芙蓉王妃安知晓:高频感应加热

Introduction介绍
Induction heating is a non-contact heating process. 感应加热是一种非接触式的加热过程。It uses high frequency electricity to heat materials that are electrically conductive. 它使用高频电加热材料,将其可导电的。Since it is non-contact, the heating process does not contaminate the material being heated. 因为它是接触、加热过程中不污染物料被加热。It is also very efficient since the heat is actually generated inside the workpiece. 它也是非常有效的自从热队实际上是内部产生的工件。This can be contrasted with other heating methods where heat is generated in a flame or heating element, which is then applied to the workpiece. 这可以与其他供热方法对比,那里高温产生于火焰或加热元件,然后应用于工件。For these reasons Induction Heating lends itself to some unique applications in industry.由于这些原因感应加热适合一些独特的应用的工业产品。
 
How does Induction Heating work ?感应加热如何工作?
A source of high frequency electricity is used to drive a large alternating current through a coil. 源高频电是用来开一辆大型交流电通过线圈。This coil is known as the work coil. 亥姆霍兹线圈被称为工作线圈。See the picture opposite.看到那张图相反。
The passage of current through this coil generates a very intense and rapidly changing magnetic field in the space within the work coil. 通过电流通过亥姆霍兹线圈产生一场激烈的及快速变化的磁场分布的工作空间内卷。The workpiece to be heated is placed within this intense alternating magnetic field.工件进行加热放置在交变磁场强烈的痛苦。
Depending on the nature of the workpiece material, a number of things happen...根据工作性质,工件的资料,很多事情发生…

The alternating magnetic field induces a current flow in the conductive workpiece. 交变磁场的流动产生电流导电的工件。The arrangement of the work coil and the workpiece can be thought of as an electrical transformer. 工作的安排线圈工件能被认为是电子变压器。The work coil is like the primary where electrical energy is fed in, and the workpiece is like a single turn secondary that is short-circuited. 工作和主线圈电能被输入进去的地方,工件像同一只把二次那是造成短路。This causes tremendous currents to flow through the workpiece. 这造成了巨大的电流流到工件。These are known as eddy currents.这些被称为涡流。
In addition to this, the high frequency used in induction heating applications gives rise to a phenomenon called skin effect. 此外,使用高频感应加热应用程序产生一种叫做皮肤的效果。This skin effect forces the alternating current to flow in a thin layer towards the surface of the workpiece. 这迫使交流电肤效应中运转对薄层表面的工件。The skin effect increases the effective resistance of the metal to the passage of the large current. 皮肤效果增加了金属的有效抵抗课文的大电流。Therefore it greatly increases the heating effect caused by the current induced in the workpiece.因此热效应,极大地提高了造成当前感应的工件。

(Although the heating due to eddy currents is desirable in this application, it is interesting to note that transformer manufacturers go to great lengths to avoid this phenomenon in their transformers. (尽管加热由于涡流是可取的,在这个应用程序,有趣的是,要注意变压器生产商要竭尽全力避免这一现象对他们的变压器。Laminated transformer cores, powdered iron cores and ferrites are all used to prevent eddy currents from flowing inside transformer cores. 层合变压器滤芯,铁粉岩心和铁素体都用于预防涡流从流出内变压器核心。Inside a transformer the passage of eddy currents is highly undesirable because it causes heating of the magnetic core and represents power that is wasted.)在变压器通过涡流极不相宜,因为它会引起热磁核心和代表力量,被浪费掉了。)
 
And for Ferrous metals ?和黑色金属吗?
For ferrous metals like iron and some types of steel, there is an additional heating mechanism that takes place at the same time as the eddy currents mentioned above. 为黑色金属如铁和某些类型的钢,还有一个额外的加热机理发生的同时涡流提到的之外。The intense alternating magnetic field inside the work coil repeatedly magnetises and de-magnetises the iron crystals. 强烈的交变磁场在工作magnetises和de-magnetises反复线圈铁晶体。This rapid flipping of the magnetic domains causes considerable friction and heating inside the material. 这种快速的反转引起的磁域内的摩擦和加热材料。Heating due to this mechanism is known as Hysteresis loss, and is greatest for materials that have a large area inside their B-H curve. 加热由于该机构是被称为滞回损失,是最大的材料,都拥有大面积在他们的B-H曲线。This can be a large contributing factor to the heat generated during induction heating, but only takes place inside ferrous materials. 这是一个大的因素,感应加热过程中产生的热,但只有发生在黑色的材料。For this reason ferrous materials lend themselves more easily to heating by induction than non-ferrous materials.因为这个原因黑色金属材料让他们更容易感应加热比非金属材料。
It is interesting to note that steel looses its magnetic properties when heated above approximately 700°C. 有趣的是,要注意钢失去它的磁性受热后约700人以上°C。This temperature is known as the Curie temperature. 这个温度就被称为·居里温度。This means that above 700°C there can be no heating of the material due to hysteresis losses. 这意味着700°C以上,就不可能有加热的物质由于磁滞损耗。Any further heating of the material must be due to induced eddy currents alone. 任何进一步的加热的物质一定是由诱导涡流孤独。This makes heating steel above 700°C more of a challenge for the induction heating systems. 这使得700°C以上加热钢更多的是一种挑战感应加热系统。The fact that copper and Aluminium are both non-magnetic and very good electrical conductors, can also make these materials a challenge to heat efficiently. 铜和铝的事实都是采用非磁性和很好的电导体,也可以使这些材料热,这是一个挑战,效率高。(We will see that the best course of action for these materials is to up the frequency to exaggerate losses due to the skin effect.)(我们会发现最佳的行动对这些材料的频率,夸大造成皮肤效果。)
 
What is Induction Heating used for ?什么是感应加热被用来做什么?
Induction heating can be used for any application where we want to heat an electrically conductive material in a clean, efficient and controlled manner.感应加热能被用在任何应用程序中我们想要热导电材料的清洁、高效、受控的方式。
One of the most common applications is for sealing the anti-tamper seals that are stuck to the top of medicine and drinks bottles. 最常见的一种应用程序的密封anti-tamper印上粘滞的医学、饮料瓶子。A foil seal coated with "hot-melt glue" is inserted into the plastic cap and screwed onto the top of each bottle during manufacture. 一个金属密封涂以“法胶水插入到塑料帽和完蛋了门楣上沿,每个瓶子在生产。These foil seals are then rapidly heated as the bottles pass under an induction heater on the production line. 这些箔密封,然后迅速加热下经过的瓶子的感应加热生产线上。The heat generated melts the glue and seals the foil onto the top of the bottle. 热气的融胶水和封衬托的上部瓶子。When the cap is removed, the foil remains providing an airtight seal and preventing any tampering or contamination of the bottle's contents until the customer pierces the foil.当帽子被移走,锡箔纸仍然提供密闭密封、防止篡改或污染的瓶子的内容,直到客户刺入金属箔上。
Another common application is "getter firing" to remove contamination from evacuated tubes such as TV picture tubes, vacuum tubes, and various gas discharge lamps. 另一个共同的应用是“吸附发射“清除污染疏散管。如有电视画面管、真空管,各种气体放电灯。A ring of conductive material called a "getter" is placed inside the evacuated glass vessel. 导电材料的戒指被称为“吸附”是贴在疏散玻璃容器。Since induction heating is a non-contact process it can be used to heat the getter that is already sealed inside a vessel. 因为感应加热是一种非接触式的过程,它可以用来加热吸附已经是在一个密封的容器。An induction work coil is located close to the getter on the outside of the vacuum tube and the AC source is turned on. 感应工作线圈是位于靠近吸附在真空管和AC电源打开。Within seconds of starting the induction heater, the getter is heated white hot, and chemicals in its coating react with any gasses in the vacuum. 数秒之内从感应热水器、吸附加热白色热,化学反应核燃料的任何气体真空。The result is that the getter absorbs any last remaining traces of gas inside the vacuum tube and increases the purity of the vacuum.这样做的结果是最后存留吸附吸收任何内气体的痕迹,增加的真空管纯净的真空。
Yet another common application for induction heating is a process called Zone purification used in the semiconductor manufacturing industry. 另一个常见应用感应加热过程被称为区净化用于半导体制造业。This is a process in which silicon is purified by means of a moving zone of molten material. 这是一个过程,在此过程中,硅净化,通过一个移动区熔化的材料。An Internet Search is sure to turn up more details on this process that I know little about.国际互联网搜索的一定会出现更多的细节,就我所知甚少这样的过程。
Other applications include melting, welding and brazing or metals. 其他的应用包括熔化、焊接和钎焊或金属。Induction cooking hobs and rice cookers. 感应烹饪hobs和大米烹饪。Metal hardening of ammunition, gear teeth, saw blades and drive shafts, etc are also common applications because the induction process heats the surface of the metal very rapidly. 金属硬化的弹药、齿轮牙,锯片和传动轴等也常用的感应加热过程中由于金属表面非常快。Therefore it can be used for surface hardening, and hardening of localised areas of metallic parts by "outrunning" the thermal conduction of heat deeper into the part or to surrounding areas. 由此可以用于表面硬度,硬金属部分的局部地区由“防热导”热深入到部分或周围的区域。The non contact nature of induction heating also means that it can be used to heat materials in analytical applications without risk of contaminating the specimen. 性质的非接触式感应加热也意味着它可以用于加热材料在分析应用没有风险挥发这标本。Similiarly, metal medical instruments may be sterilised by heating them to high temperatures whilst they are still sealed inside a known sterile environment, in order to kill germs.Similiarly、金属医疗器械可以由无菌高温加热而他们仍然在一个密封的已知的无菌的环境时,为了杀细菌。
 
What is required for Induction Heating ?什么是必需的感应暖气设备吗?
In theory only 3 things are essential to implement induction heating:在理论上是必要的,只有三件事实施感应加热:
A source of High Frequency electrical power,源高频电力之时, A work coil to generate the alternating magnetic field,工作线圈产生交变磁场, An electrically conductive workpiece to be heated,导电工件进行加热,
Having said this, practical induction heating systems are usually a little more complex. 马大说了这话、实用感应加热系统通常稍微复杂了一些。For example, an impedance matching network is often required between the High Frequency source and the work coil in order to ensure good power transfer. 例如,一个阻抗匹配网络之间经常需要高频率源和工作线圈以确保具有良好的力量转移。Water cooling systems are also common in high power induction heaters to remove waste heat from the work coil, its matching network and the power electronics. 水冷系统也共同在大功率异步加热器除去废热从工作线圈,与之相匹配的网络和电力电子。Finally some control electronics is usually employed to control the intensity of the heating action, and time the heating cycle to ensure consistent results. 最后一些控制电子是控制通常采用高强度的加热作用,和时间加热周期计划一致的结果。The control electronics also protects the system from being damaged by a number of adverse operating conditions. 控制电子还可以保护系统不受损坏有许多不良的操作条件。However, the basic principle of operation of any induction heater remains the same as described earlier.然而,基本的工作原理是一样的任何感应热水器所描述的更早。
 
Practical implementation切实实施
In practice the work coil is usually incorporated into a resonant tank circuit. 在实践中,工作线圈通常是合并到共振坦克电路。This has a number of advantages. 这有许多优点。Firstly, it makes either the current or the voltage waveform become sinusoidal. 首先,它使或电流、电压波形成为正弦。This minimises losses in the inverter by allowing it to benefit from either zero-voltage-switching or zero-current-switching depending on the exact arrangement chosen. 这互信的逆变器的损失由允许它受益zero-voltage-switching或zero-current-switching也取决于准确的安排的选择。The sinusoidal waveform at the work coil also represents a more pure signal and causes less Radio Frequency Interference to nearby equipment. 正弦波形在工作卷还代表了一个更加纯净信号和原因射频干扰少到附近的设备。This later point becoming very important in high-powered systems. 这后来又点日益重要大功率系统。We will see that there are a number of resonant schemes that the designer of an induction heater can choose for the work coil:我们会看到目前仍有不少共振方案设计师感应加热可以选择工作缠绕:
 
Series resonant tank circuit系列谐振坦克电路
The work coil is made to resonate at the intended operating frequency by means of a capacitor placed in series with it. 工作了线圈产生共振操作频率本利用电容放置在系列。This causes the current through the work coil to be sinusoidal. 这使得电流通过工作线圈视为正弦。The series resonance also magnifies the voltage across the work coil, far higher than the output voltage of the inverter alone. 系列谐振也夸大了工作电压,远远高于线圈的逆变器的输出电压独自一人。The inverter sees a sinusoidal load current but it must carry the full current that flows in the work coil. 变频器看到一个正弦负荷电流但必须把全部的电流流过工作线圈。For this reason the work coil often consists of many turns of wire with only a few amps or tens of amps flowing. 因为这个原因工作线圈通常包括多次转变的电线只有几个安培的电流或数十安培的流动。Significant heating power is achieved by allowing resonant voltage rise across the work coil in the series-resonant arrangement whilst keeping the current through the coil (and the inverter) to a sensible level.重要的热力获得是通过允许共振电压上升的线圈在工作series-resonant安排而保持的电流流过线圈(及逆变器)使企业保持水平。
This arrangement is commonly used in things like rice cookers where the power level is low, and the inverter is located next to the object to be heated. 这个安排常用的饭箱之类的东西在较低,功率电平逆变器工作位置紧邻对象进行加热。The main drawbacks of the series resonant arrangement are that the inverter must carry the same current that flows in the work coil. 主要缺点系列谐振安排是逆变器必须携带同一电流流经在工作中线圈。In addition to this the voltage rise due to series resonance can become very pronounced if there is not a significantly sized workpiece present in the work coil to damp the circuit. 除此之外,由于电压上升系列谐振可以变得非常明显如果没有明显存在于工作工件尺寸线圈潮湿的这条赛道。This is not a problem in applications like rice cookers where the workpiece is always the same cooking vessel, and its properties are well known at the time of designing the system.这个问题不是在应用在工件像大米炊具炊具永远都是一样的,并对其特性进行很了解这种病的设计的系统。
The tank capacitor is typically rated for a high voltage because of the resonant voltage rise experienced in the series tuned resonant circuit. 坦克电容器通常适用高压因为谐振电压上升在经历了系列谐振电路,调整。It must also carry the full current carried by the work coil, although this is typically not a problem in low power applications.它必须承担全部当前所携带的工作线圈,尽管这是一个问题一般都不是低功率的应用。
 
Parallel resonant tank circuit坦克并联谐振电路
The work coil is made to resonate at the intended operating frequency by means of a capacitor placed in parallel with it. 工作了线圈产生共振操作频率本利用电容放置在平行。This causes the current through the work coil to be sinusoidal. 这使得电流通过工作线圈视为正弦。The parallel resonance also magnifies the current through the work coil, far higher than the output current capability of the inverter alone. 平行共振还增加当前通过工作线圈,大大高于美国的逆变器的输出电流能力独自一人。The inverter sees a sinusoidal load current. 变频器看到一个正弦负荷电流。However, in this case it only has to carry the part of the load current that actually does real work. 然而,在这种情况下它只是有带负载电流的部分,实际上是真正的工作。The inverter does not have to carry the full circulating current in the work coil. 逆变器工作没有携带完整的循环电流在工作线圈。This is very significant since power factors in induction heating applications are typically low. 这是非常重要的因为功率因数感应加热应用是典型的低。This property of the parallel resonant circuit can make a tenfold reduction in the current that must be supported by the inverter and the wires connecting it to the work coil. 这个属性的平行谐振电路,能使十倍的减少必须支持的电流通过变频器与电线连接到工作线圈。Conduction losses are typically proportional to current squared, so a tenfold reduction in load current represents a significant saving in conduction losses in the inverter and associated wiring. 办理损失通常与10平方,所以目前对负载电流的减少是一种重要的储蓄在办理损失相关变频器及线路。This means that the work coil can be placed at a location remote from the inverter without incurring massive losses in the feed wires.这意味着工作线圈刊登在一个位置远离逆变器不产生巨大损失在饲料电线。
Work coils using this technique often consist of only a few turns of a thick copper conductor but with large currents of many hundreds or thousands of amps flowing. 工作线圈使用这项技术经常由只有几把一个粗铜导体,但许多大电流的成百上千的电流的流动。(This is necessary to get the required Ampere turns to do the induction heating.) (这是必要的,所需要的安培转感应加热。)Water cooling is common for all but the smallest of systems. 水冷却是常见的为所有,但最小的系统。This is needed to remove excess heat generated by the passage of the large high frequency current through the work coil and its associated tank capacitor.只有这样,才能清除多余的热气通过大的高频电流通过工作线圈及相关的坦克电容器。

In the parallel resonant tank circuit the work coil can be thought of as an inductive load with a "power factor correction" capacitor connected across it. 坦克在并联谐振电路工作线圈可看成是个感性负载与“功率因数校正”电容器连接通过。The PFC capacitor provides reactive current flow equal and opposite to the large inductive current drawn by the work coil. 全氟化碳的电容器提供无功电流的流动相同和相反的大画的感应电流工作线圈。The key thing to remember is that this huge current is localised to the work coil and its capacitor, and merely represents reactive power sloshing back-and-forth between the two. 关键要记住的是,这个巨大的电流线圈及对工作的局部的电容器,仅仅象征着无功功率来回晃动的两者之间的。Therefore the only real current flow from the inverter is the relatively small amount required to overcome losses in the "PFC" capacitor and the work coil. 所以唯一的真正的电流从逆变器,所需金额比较小的损失克服“全氟化碳的“电容器和工作线圈。There is always some loss in this tank circuit due to dielectric loss in the capacitor and skin effect causing resistive losses in the capacitor and work coil. 总有一些损失由于这种膨胀罐电路在电容和变压器油介损的趋肤效应造成电阻的损耗,电容和工作线圈。Therefore a small current is always drawn from the inverter even with no workpiece present. 因此,小电流总是来自逆变器即使没有工件的礼物。When a lossy workpiece is inserted into the work coil, this damps the parallel resonant circuit by introducing a further loss into the system. 当一个有损工件插入到工作线圈,这个会遏制并联谐振电路,通过引入一个更大的损失到系统中。Therefore the current drawn by the parallel resonant tank circuit increases when a workpiece is entered into the coil.因此当前制定由并联谐振电路增加坦克时进入工件卷。
 
Impedance matching阻抗匹配
Or simply "Matching". This refers to the electronics that sits between the source of high frequency power and the work coil we are using for heating. 或者仅仅是“匹配”。这涉及到电子位于的来源之间高频大功率和工作线圈,我们使用取暖。In order to heat a solid piece of metal via induction heating we need to cause a TREMENDOUS current to flow in the surface of the metal. 为了热一块实心的金属通过感应加热我们需要引起巨大的电流流的金属表面。However this can be contrasted with the inverter that generates the high frequency power. 然而这可以与生成逆变器高频大功率。The inverter generally works better (and the design is somewhat easier) if it operates at fairly high voltage but a low current. 变频器一般运作得更好(而设计有点容易)如果它的运作是相当高的电压但低电流。(Typically problems are encountered in power electronics when we try to switch large currents on and off in very short times.) (通常是问题出现在电力电子当我们试图开关断断续续的大电流在很短的时间。)Increasing the voltage and decreasing the current allows common switch mode MOSFETs (or fast IGBTs) to be used. 增加电压和减少当前允许常见的转换模式mosfet(或快IGBTs),使用寿命长。The comparatively low currents make the inverter less sensitive to layout issues and stray inductance. 比较低流让逆变器较不敏感的布局问题和电感。It is the job of the matching network and the work coil itself to transform the high-voltage/low-current from the inverter to the low-voltage/high-current required to heat the workpiece efficiently.工作配比网络和工作将自身盘卷将高压/电流的从变频低压/支大电流须加热工件效率。
We can think of the tank circuit incorporating the work coil (Lw) and its capacitor (Cw) as a parallel resonant circuit.我们可以把坦克电路将工作圈(妳)和它的电容器(连续波)并联谐振电路。
This has a resistance (R) due to the lossy workpiece coupled into the work coil due to the magnetic coupling between the two conductors.这电阻(R)由于有损工件耦合至工作线圈由于两者之间的磁耦合导体。
See the schematic opposite.看到该电路的相反。

In practice the resistance of the work coil, the resistance of the tank capacitor, and the reflected resistance of the workpiece all introduce a loss into the tank circuit and damp the resonance. 在实践工作的阻力线圈,其电阻,电容罐的抗反射工件所有介绍一种损失进油箱电路和潮湿的共振。Therefore it is useful to combine all of these losses into a single "loss resistance." 因此它是有用的,将所有的这些损失为一个“损失抵抗。”In the case of a parallel resonant circuit this loss resistance appears directly across the tank circuit in our model. 如果这一损失谐振电路,平行的阻力直接出现在坦克电路在我们的典范。This resistance represents the only component that can consume real power, and therefore we can think of this loss resistance as the load that we are trying to drive power into in an efficient manner.该电阻代表唯一真正的力量,它可以消耗组成部分,因此我们可以认为这种损失阻力负荷,我们想把能力以一种有效的方式。

When driven at resonance the current drawn by the tank capacitor and the work coil are equal in magnitude and opposite in phase and therefore cancel each other out as far as the source of power is concerned.在共振电流驱动时画的坦克电容器和工作线圈是平等的在大小和相对相位一致,因此彼此对消出去,直到力量的来源是有关的。This means that the only load seen by the power source at the resonant frequency is the loss resistance across the tank circuit.这意味着只有负荷被电源在共振频率阻力是丧失在坦克电路。(Note that, when driven either side of the resonant frequency, there is an additional "out-of-phase" component to the current caused by incomplete cancellation of the work coil current and the tank capacitor current. (注意:驱动时的共振频率的两边,还有一个额外的“异相当前部分造成不完全取消工作线圈电流、槽内电容电流。This reactive current increases the total magnitude of the current being drawn from the source but does not contribute to any useful heating in the workpiece.)这无功电流的大小总额增加了电流为来自源,但不造成任何有用的加热工件。)
The job of the matching network is simply to transform this relatively large loss resistance across the tank circuit down to a lower value that better suits the inverter attempting to drive it. 匹配网络的工作仅仅是将这相对较大的阻力损失在坦克电路到较低的价值,更适合变频器试图开车。There are many different ways to achieve this impedance transformation including tapping the work coil, using a ferrite transformer, a capacitive divider in place of the tank capacitor, or a matching circuit such as an L-match network.有很多不同的方法实现这一阻抗变革包括开发工作线圈,用铁素体变压器、一个电容分压器代替坦克电容器、或匹配电路,如一个L-match网络。
In the case of an L-match network it can transform the relatively high load resistance of the tank circuit down to something around 10 ohms which better suits the inverter. 如果它能转变L-match网络相对较高的容器的负载电阻电路下来大概10欧姆,更适合变频器。This figure is typical to allow the inverter to run from several hundred volts whilst keeping currents down to a medium level so that standard switch-mode MOSFETs can be used to perform the switching operation.这个数字是典型的允许逆变器逃避几百伏特而保持电流到中等水平以便标准大多数的开关型mosfet可以用来做转换操作。
The L-match network consists of components Lm and Cm shown opposite.L-match网络遍及组件的显示和厘米的激光束相反。

The L-match network has several highly desirable properties in this application. L-match的网络有几个非常可取的性能在这申请。The inductor at the input to the L-match network presents a progressively rising inductive reactance to all frequencies higher than the resonant frequency of the tank circuit. 做成电感器在输入逐步上升L-match网络提出了感应电抗引入高于所有频率谐振频率容器的电路。This is very important when the work coil is to be fed from a voltage-source inverter that generates a squarewave voltage output. 这是非常重要的,当工作饲料的线圈从voltage-source逆变器产生squarewave输出电压。Here is an explanation of why this is so…这是一种解释,为什么是这样的…
The squarewave voltage generated by most half-bridge and full-bridge circuits is rich in high frequency harmonics as well as the wanted fundamental frequency. 所产生的电压squarewave半桥电路,最丰富的高频率以及希望基本频率。Direct connection of such a voltage source to a parallel resonant circuit would cause excessive currents to flow at all harmonics of the drive frequency! 这样的直接连接的电压源的平行谐振电路,将导致过度的电流流在所有谐波的驱动频率!This is because the tank capacitor in the parallel resonant circuit would present a progressively lower capacitive reactance to increasing frequencies. 这是因为坦克电容器在平行谐振电路,要将一个逐步降低电容式电抗引入增加频率。This is potentially very damaging to a voltage-source inverter. 这是一个非常有害的潜在voltage-source变频器。It results in large current spikes at the switching transitions as the inverter tries to rapidly charge and discharge the tank capacitor on rising and falling edges of the squarewave. 它导致大电流峰值在开关转换为逆变器试图迅速充放电坦克电容对上升和下降squarewave的边缘。The inclusion of the L-match network between the inverter and the tank circuit negates this problem. 包括了L-match网络之间、槽的逆变器电路否认这个问题。Now the output of the inverter sees the inductive reactance of Lm in the matching network first, and all harmonics of the drive waveform see a gradually rising inductive impedance. 现在的逆变器的输出看到在Lm的感应电抗引入网络第一,和所有匹配谐波驱动波形看到一个日渐崛起的感应阻抗。This means that maximum current flows at the intended frequency only and little harmonic current flows, making the inverter load current into a smooth waveform.这意味着最大电流流年龄只打算频率,使小谐波电流流逆变均匀负载电流波形。
Finally, with correct tuning the L-match network is able to provide a slight inductive load to the inverter. 最后,以正确的调整L-match网络能提供轻微的感性负载到变频器。This slightly lagging inverter load current can facilitate Zero-Voltage-Switching (ZVS) of the MOSFETs in the inverter bridge. 负载电流略微落后的逆变器能促进的Zero-Voltage-Switching(零电压逆变器的钳桥。This significantly reduces turn-on switching losses due to device output capacitance in MOSFETs operated at high voltages. 这大大降低刺激的开关损耗由于设备输出电容在mosfet运行在高电压。The overall result is less heating in the semiconductors and increased lifetime.整体的结果不加热半导体和增加了一生。
In summary, the inclusion of an L-match network between the inverter and the parallel resonant tank circuit achieves two things.总之,这其中包括L-match之间的网络和并联谐振逆变电路实现坦克两件事。
Impedance matching so that the required amount of power can be supplied from the inverter to the workpiece,阻抗匹配,使需要量的电源可以直接来自变频器与工件, Presentation of a rising inductive reactance to high frequency harmonics to keep the inverter safe and happy.介绍一个崛起中的感应电抗引入高频率保持逆变器安全与快乐。
Looking at the previous schematic above we can see that the capacitor in the matching network (Cm) and the tank capacitor (Cw) are both in parallel. 看着以前的电路图中,我们可以看出,电容器在匹配网络(Cm)、槽内电容器(连续波)都在平行。In practice both of these functions are usually accomplished by a single purpose built power capacitor. 实际上这两种功能通常是一个单一的目的建造了电力电容器。Most of its capacitance can be thought of as being in parallel resonance with the work coil, with a small amount providing the impedance matching action with the matching inductor (Lm.) 大多数的电容可以看成是并联共振与工作线圈,有少量的行动提供的阻抗匹配的匹配电感(激光束。)Combing these two capacitances into one leads us to arrive at the LCLR model for the work coil arrangement, which is commonly used in industry for induction heating.这两个只结合成一个引领我们到达LCLR模型线圈安排工作,也就是一般用于工业感应加热。

 
The LCLR work coilLCLR线圈的工作
This arrangement incorporates the work coil into a parallel resonant circuit and uses the L-match network between the tank circuit and the inverter. 这个安排了工作卷成一个并联谐振电路,采用网络之间的L-match坦克电路和变频器。The matching network is used to make the tank circuit appear as a more suitable load to the inverter, and its derivation is discussed in the section above.匹配网络是用来使坦克电路出现更合适的荷载逆变、生成了部分以上。
The LCLR work coil has a number of desirable properties:LCLR线圈的工作有一定数量的理想的特性:
A huge current flows in the work coil, but the inverter only has to supply a low current. 一个巨大的电流在工作中线圈,但变频器只有提供一种低电流。The large circulating current is confined to the work coil and its parallel capacitor, which are usually located very close to each other.大型循环电流限于工作线圈及其并联电容器,通常位于彼此非常接近。 Only comparatively low current flows along the transmission line from the inverter to the tank circuit, so this can use lighter duty cable.只有相对较低的电流沿传输线从变频器在罐电路,所以这只能用轻责任电缆。 Any stray inductance of the transmission line simply becomes part of the matching network inductance (Lm.) 任何电感的输电线路简单地成为匹配网络电感的激光束。)Therefore the heat station can be located away from the inverter.因此热车站完全可以距变频器。 The inverter sees a sinusoidal load current so it can benefit from ZCS or ZVS to reduce its switching losses and therefore run cooler.变频器看到一个正弦负荷电流,所以它能受益于ZCS减少或零电压开关损耗,因此,运行冷却器。 The series matching inductor can be altered to cater for different loads placed inside the work coil.系列匹配电感都会被更改以迎合不同的负载都放置在工作线圈。 The tank circuit can be fed via several matching inductors from many inverters to reach power levels above those achievable with a single inverter. 坦克电路可以喂养通过几个匹配电感器外,还可以从许多功率电平逆变器达到上述可达到的单一变频器。The matching inductors provide inherent sharing of the load current between the inverters and also make the system tolerant to some mismatching in the switching instants of the paralleled inverters.匹配电感器提供内在分享负载电流的逆变器之间,同时使系统能在开关瞬发源于一些平行的应用。
For more information about the behaviour of the LCLR resonant network see the new section below labelled "LCLR network frequency response."提供更多有关的行为共振LCLR网络可以看到新的参考下述标为“LCLR网络频率回应。”
Another advantage of the LCLR work coil arrangement is that it does not require a high-frequency transformer to provide the impedance matching function. LCLR工作的另一个好处是,它线圈安排高频变压器不需要提供阻抗匹配功能。Ferrite transformers capable of handling several kilowatts are large, heavy and quite expensive. 铁氧体变压器有能力处理几千瓦是大的,重,太贵了。In addition to this, the transformer must be cooled to remove excess heat generated by the high currents flowing in its conductors. 此外,变压器必须冷却到热气去除多余的高电流流在它的导体。The incorporation of the L-match network into the LCLR work coil arrangement removes the necessity of a transformer to match the inverter to the work coil, saving cost and simplifying the design. 公司成立的L-match网络纳入到LCLR线圈安排工作的必要性解除变压器匹配的逆变器的工作线圈,降低成本、简化设计。However, the designer should appreciate that a 1:1 isolating transformer may still be required between the inverter and the input to the LCLR work coil arrangement if electrical isolation is necessary from the mains supply. 然而,设计人应懂得1:1隔离变压器可能仍然被要求变频器与之间的输入工作LCLR线圈安排是必要的,如果电气隔离电源供应。This depends whether isolation is important, and whether the main PSU in the induction heater already provides sufficient electrical isolation to meet these safety requirements.是否要隔离是重要的,是否在感应热水器主要大学已经提供了足够的电气隔离符合这些安全要求。
 
Conceptual schematic概念原理
The system schematic belows shows the simplest inverter driving its LCLR work coil arrangement.以下材料显示系统原理的最简单的变频驱动LCLR线圈的工作安排。

Note that this schematic DOES NOT SHOW the MOSFET gate-drive circuitry and control electronics!注意此原理并没有显示gate-drive场效应晶体管电路和控制电子装置!
 
The inverter in this demonstration prototype was a simple half-bridge consisting of two MTW14N50 MOSFETs made my On-semiconductor (formerly Motorola.) 变频器在这次示威的原型是一个简单由两个半MTW14N50 mosfet使我的On-semiconductor(原摩托罗拉。)It is fed from a smoothed DC supply with decoupling capacitor across the rails to support the AC current demands of the inverter. 从一个平滑的输入直流电源去耦电容铁轨上支持交流电流的需求变频器。However, it should be realised that the quality and regulation of the power supply for induction heating applications is not critical. 但是,它应该意识到,质量和规律的感应加热应用电力供应并不苛刻。Full-wave rectified (but un-smoothed) mains can work as well as smoothed and regulated DC when it comes to heating metal, but peak currents are higher for the same average heating power. 全纠正(但un-smoothed)水管可以工作以及抚平,稳压直流谈到加热金属,但是峰值电流提高是同样的普通热力。There are many arguments for keeping the size of the DC bus capacitor down to a minimum. 有许多理由让直流母线的大小电容器到最低限度。In particular it improves the power factor of current drawn from the mains supply via a rectifier, and it also minimises stored energy in case of fault conditions within the inverter.它尤其提高功率因数的电流通过来自供电线路组成的,它也存储能量的互信的故障状态下时在变频器。
The DC-blocking capacitor is used merely to stop the DC output from the half-bridge inverter from causing current flow through the work coil. 使用DC-blocking电容器的仅仅是为了阻止直流输出从半桥逆变器所造成的工作电流流过线圈。It is sized sufficiently large that it does not take part in the impedance matching, and does not adversely effect the operation of the LCLR work coil arrangement.这是大小的足够大,它不参加阻抗匹配,不不良影响工作LCLR的操作线圈的安排。
 
In high power designs it is common to use a full-bridge (H-bridge) of 4 or more switching devices. 在大功率设计通常用一个桥(H-bridge四或更多的开关。In such designs the matching inductance is usually split equally between the two bridge legs so that the drive voltage waveforms are balanced with respect to ground. 在这样设计匹配电感通常是分裂的两个桥之间的平等双腿,以便你的驱动电压波形是平衡就地面。The DC-blocking capacitor can also be eliminated if current mode control is used to ensure that no net DC flows between the bridge legs. 这DC-blocking电容器也可以被淘汰如果当前模式控件可用来确保没有净直流之间流动时,这座桥腿。(If both legs of the H-bridge can be controlled independently then there is scope for controlling power throughput using phase-shift control. (如果双腿的H-bridge可独立控制还有吞吐量控制能力范围使用离散控制。See point 6 in the section below about "Power control methods" for further details.)看下文在6点关于“功率控制方法”)为进一步的细节。

 
At still higher powers it is possible to use several seperate inverters effectively connected in parallel to meet the high load-current demands. 在更高的力量就可能使用几个独立有效逆变器并联连接于load-current满足更高要求。However, the seperate inverters are not directly tied in parallel at the output terminals of their H-bridges. 然而,分离变频器平行没有直接关系的H-bridges的输出端子。Each of the distributed inverters is connected to the remote work coil via its own pair of matching inductors which ensure that the total load is spread evenly among all of the inverters.每一个分布式逆变器连线到远端工作线圈通过其自己的一双匹配电感就是保证总负载的传播是均匀分布于所有的应用。

These matching inductors also provide a number of additional benefits when inverters are paralleled in this way. 这些匹配电感器也提供大量的额外收益逆变器时平行。Firstly, the impedance BETWEEN any two inverter outputs is equal to twice the value of the matching inductance. 首先,任何两个之间的阻抗逆变器的输出的价值将双倍的匹配电感。This inductive impedance limits the "shoot between" current that flows between paralleled inverters if their switching instants are not perfectly synchronised. 这感应阻抗限制了《射之间的“电流并联变频器之间流动时,如果他们并不完全同步开关瞬间。Secondly, this same inductive reactance between inverters limits the rate at which fault current rises if one of the inverters exhibits a device failure, potentially eliminating failure of further devices. 其次,这个之间感应电抗引入逆变器的速度限制故障电流上升如果变频器,潜在的设备故障展示了一种消除失败的进一步的设备。Finally, since all distributed inverters are already connected via inductors, any additional inductance between the inverters merely adds to this impedance and only has the effect of slightly degrading current sharing. 最后,因为所有的分布已连接针对逆变器通过电感器,任何额外的电感之间仅仅增加了变频器此阻抗的影响,仅略降解当前共享。Therefore the distributed inverters for induction heating need not necessarily be located physically close to each other. 因此分布式逆变器为感应加热,不一定是位于身体上的接触到每一个人。If isolation transformers are included in the designs then they need not even run from the same supply!如果隔离变压器设计包括那时,你就再也不必甚至跑同一供应!
 
Fault tolerance容错
The LCLR work coil arrangement is very well behaved under a variety of possible fault conditions.LCLR线圈的工作安排很表现得好下的各种可能发生的故障条件。
Open circuit work coil.开断工作线圈。 Short circuit work coil, (or tank capacitor.)线圈短路工作,(或坦克电容器。) Shorted turn in work coil.将缩短工作线圈。 Open circuit tank capacitor.开断坦克电容器。
All of these failures result in an increase in the impedance being presented to the inverter and therefore a corresponding drop in the current drawn from the inverter. 所有这些失败导致的阻抗的增加被介绍与变频器,因此在当前相应下降来自变频器。The author has personally used a screwdriver to short-circuit between turns of a work coil carrying several hundred amps. 作者亲自用螺丝刀之间短路造成的转向工作线圈提着几名电流。Despite sparks flying at the location of the applied short-circuit, the load on the inverter is reduced and the system survives this treatment with ease.尽管火花飞在应用的位置上荷载短路、过的逆变器,减少了系统在这治疗与安心。
The worst thing that can happen is that the tank circuit becomes detuned such that its natural resonant frequency is just above the operating frequency of the inverter. 最可怕的事情是,坦克电路变得失谐,这样它的自然的谐振频率就在上面操作频率的变频器。Since the drive frequency is still close to resonance there is still significant current flow out of the inverter. 因为驱动频率仍接近共振电流仍然很大的变频器。But the power factor is reduced due to the detuning, and the inverter load-current begins to lead the voltage. 但功率因数降低由于,变频器的失谐load-current开始带领电压。This situation is undesirable because the load current seen by the inverter changes direction before the applied voltage changes. 这种情况是不受欢迎的,因为负荷电流被检测者看到的逆变器会改变方向在电压的变化。The outcome of this is that current is force-commutated between free-wheel diodes and the opposing MOSFET every time the MOSFET is turned on. 结果是,电流之间force-commutated free-wheel二极管和对方MOSFET每次打开场效应晶体管。This causes a forced reverse recovery of the free-wheel diodes whilst they are already carrying significant forward current. 这导致了一强迫反向恢复的free-wheel二极管而他们已经带着重要的前锋电流。This results in a large current surge through both the diode and the opposing MOSFET that is turning on.这样就导致了大电流激增,经过两个二极管和反对MOSFET,也就是如何转变。
Whilst not a problem for special fast recovery rectifiers, this forced recovery can cause problems if the MOSFETs intrinsic body diodes are used to provide the free-wheel diode function. 虽然没有什么问题,但是对于特殊快恢复二极管、这些强迫的复苏可能会造成问题如果mosfet内在的身体二极管是用来提供free-wheel二极管的功能。These large current spikes still represent a significant power loss and threat to reliability. 这些大电流峰值还代表着重大的功率损耗和威胁的可靠性。However, it should be realised that proper control of the inverter operating frequency should ensure that it tracks the resonant frequency of the tank circuit. 但是,它应该意识到,合理控制的逆变器的操作频率应该确保它收集了谐振频率容器的电路。Therefore the leading power factor condition should ideally not arise, and should certainly not persist for any length of time. 因此,领先的电力因素状况最好应该不再起来,并应当然不是持续一段时间。The resonant frequency should be tracked up to its limit, then the system shut-down if it has wandered outside of an acceptable frequency range.人要追踪的共振频率其限制,系统关闭这头生的、若有在外边闲逛的可接受的频率范围。
 
Power control methods功率控制方法
It is often desirable to control the amount of power processed by an induction heater. 控制常常要处理的权利量的感应加热。This determines the rate at which heat energy is transferred to the workpiece. 这就决定了速率被转移到热能的工件。The power setting of this type of induction heater can be controlled in a number of different ways:电力设定的类型的感应加热可控制在多种不同的方法:
 
1. 1。Varying the DC link voltage.不同的直流环节电压。
The power processed by the inverter can be decreased by reducing the supply voltage to the inverter. 电力处理均可降低逆变电源的供应减少变频器。This can be done by running the inverter from a variable voltage DC supply such as a controlled rectifier using thyristors to vary the DC supply voltage derived from the mains supply. 这可以通过从变频器运行直流供电的变压等使用thyristors控制整流器以不同的直流电源电压供电线路中派生出来的。The impedance presented to the inverter is largely constant with varying power level, so the power throughput of the inverter is roughly proportional to the square of the supply voltage. 阻抗呈现给变频器在很大程度上不断用不同的能量水平的功能的逆变器的生产量大约是成正比的平方米的电压。Varying the DC link voltage allows full control of the power from 0% to 100%.不同的直流环节电压允许完全控制权力从0 ~ 100%。
It should be noted however, that the exact power throughput in kilowatts depends not only on the DC supply voltage to the inverter, but also on the load impedence that the work coil presents to the inverter through the matching network. 然而,值得注意的,精确的电力优化千瓦不仅取决于直流供电电压逆变器,而且还对负载线圈的工作impedence礼物逆变器通过匹配网络。Therefore if precise power control is required the actual induction heating power must be measured, compared to the requested "power setting" from the operator and an error signal fed back to continually adjust the DC link voltage in a closed-loop fashion to minimise the error. 因此,如果精确的功率控制是需要实际感应加热权力必须测量要求相比,在“权力设置“操作者的和一个错误信号反馈不断调整直流环节电压在闭环时尚降到最低的错误。This is necessary to maintain constant power because the resistance of the workpiece changes considerably as it heats up. 这是必要的,保持固定的权利因为的电阻变化很大,因为它加热工件。(This argument for closed-loop power control also applies to all of the methods that follow below.)(这个观点闭环功率控制也适用于所有的方法,遵循下文。)
 
2. 2。Varying the duty ratio of the devices in the inverter.不同的占空比的设备在变频器。
The power processed by the inverter can be decreased by reducing the on-time of the switches in the inverter. 电力处理均可降低逆变器开关的及时减少在变频器。Power is only sourced to the work coil in the time that the devices are switched on. 只有采购能力的工作时间的线圈的设备都有所增长。The load current is then left to freewheel through the devices body diodes during the deadtime when both devices are turned off. 负载电流然后留给freewheel通过设备在deadtime身体二极管当两者的装置被关上。Varying the duty ratio of the switches allows full control of the power from 0% to 100%. 不同的占空比开关的允许完全控制权力从0 ~ 100%。However, a significant drawback of this method is the commutation of heavy currents between active devices and their free-wheel diodes. 然而,一个重要的退税该方法的沉重的变换和有源装置之间的电流free-wheel二极管。Forced reverse recovery of the free-wheel diodes that can occur when the duty ratio is considerably reduced. 强迫反向恢复的free-wheel二极管,可能发生当占空比是相当的减少。For this reason duty ratio control is not usually used in high power induction heating inverters.因为这个原因占空比控制通常不用于高功率感应加热应用。
 
3. 3。Varying the operating frequency of the inverter.不同的操作频率的变频器。
The power supplied by the inverter to the work coil can be reduced by detuning the inverter from the natural resonant frequency of the tank circuit incorporating the work coil. 逆变电源供给的工作可以减少线圈失谐变频器从自然共振频率提供量身定制的容器的电路工作线圈。As the operating frequency of the inverter is moved away from the resonant frquency of the tank circuit, there is less resonant rise in the tank circuit, and the current in the work coil diminishes. 运行频率的逆变器,离开共振frquency燃料箱电路,有不少共鸣起来在坦克电路的设计与工作电流线圈不断缩水。Therefore less circulating current is induced into the workpiece and the heating effect is reduced.因此不循环电流感应到工件以及采暖效果降低。
In order to reduce the power throughput the inverter is normally detuned on the high side of the tank circuits natural resonant frequency. 为了减少电力生产能力的逆变器通常是失谐偏高燃料箱电路自然共振频率。This causes the inductive reactance at the input of the matching circuit to become increasingly dominant as the frequency increases. 这使得感应电抗引入的输入端的日益匹配电路的频率占据主导地位的增加而增加。Therefore the current drawn from the inverter by the matching network starts to lag in phase and diminish in amplitude. 因此当前来自逆变器环节匹配网络开始落后振幅和减少阶段。Both of these factors contribute to a reduction in the real power throughput. 这两种因素以减少真正的权力的吞吐量。In addition to this the lagging power factor ensures that the devices in the inverter still turn on with zero voltage across them, and there are no free-wheel diode recovery problems. 除此之外,落后的功率因数确保了设备逆变器还开零电压她们,也没有free-wheel二极管恢复问题。(This can be contrasted with the situation that would occur if the inverter were detuned on the low side of the work coil's resonant frequency. (这可以变通的情况下,会出现在失谐变频器偏低的工作线圈的共振频率。ZVS is lost, and the free-wheel diodes see forced reverse-recovery whilst carrying significant load current.)零电压的丢失了,reverse-recovery free-wheel二极管看到迫使负载电流同时携带重要。)
This method of controlling power level by detuning is very simple since most induction heaters already have control over the operating frequency of the inverter in order to cater for different workpieces and work coils. 该方法控制能力失谐水平很简单,因为大多数磁感应加热器已经控制操作频率为满足变频器在不同工件和工作线圈。The downside is that it only provides a limited range of control, as there is a limit to how fast power semiconductors can be made to switch. 它的坏处是只是提供有限的范围的控制,作为是有限制的,以多快可以功率半导体器件的转换。This is particularly true in high power applications where the devices may already be running close to maximum switching speeds. 事实也确实如此,在大功率应用在这些设备可能已经接近最大的切换运行速度。High power systems using this power control method require a detailed thermal analysis of the results of switching losses at different power levels to ensure device temperatures always stay within tolerable limits.高功率系统运用这种力量控制方法需要一份详细的热分析的结果在不同功率电平开关损耗使器件内始终保持温度可限制。
For more detailed information about power control by detuning see the new section below labelled "LCLR network frequency response."要获取更详细的信息,对电力控制下面栏目看到新的失谐标为“LCLR网络频率回应。”
 
4. 4。Varying the value of the inductor in the matching network.不同的价值在匹配电感网络。
The power supplied by the inverter to the work coil can be varied by altering the value of the matching network components. 逆变电源供给的工作线圈可以变换的价值通过改变的匹配网络组件。The L-match network between the inverter and the tank circuit technically consists of an inductive and a capacitive part. L-match之间的网络技术、槽逆变器电路由一个电感和电容式的部分。But the capacitive part is in parallel with the work coil's own tank capacitor, and in practice these are usually one and the same part. 但电容式部分是并联工作线圈的自己的坦克电容器;在实践上这些通常都是同一的部分。Therefore the only part of the matching network that is available to adjust is the inductor.因此,只有部分匹配网络调整可做成电感器。
The matching network is responsible for transforming the load impedance of the workcoil to a suitable load impedance to be driven by the inverter. 负责的匹配网络的负载阻抗转变在一个合适的负载阻抗workcoil遗志变极器。Altering the inductance of the matching inductor adjusts the value to which the load impedance is translated. 改变的电感匹配电感值的调整的负载阻抗翻译。In general, decreasing the inductance of the matching inductor causes the work coil impedance to be transformed down to a lower impedance. 一般来说,降低电感线圈电感使工作匹配阻抗的变化到较低的阻抗。This lower load impedance being presented to the inverter causes more power to be sourced from the inverter. 这更低的负载阻抗呈现于变频器引起更多的权利来源于变极器。Conversely, increasing the inductance of the matching inductor causes a higher load impedance to be presented to the inverter. 相反,增加电感的匹配电感导致更高的负载阻抗已知才能够被提交变频器。This lighter load results in a lower power flow from the inverter to the work coil.这只打火机负荷低功耗的结果流动的逆变器的工作线圈。
The degree of power control achieveable by altering the matching inductor is moderate. 功率控制的程度通过改变成为可能的匹配电感适中。There is a also a shift in the resonant frequency of the overall system - This is the price to pay for combining the L-match capacitance and tank capacitance into one unit. 有一个也改变整个系统的共振频率——这是要付出的代价为结合L-match电容和坦克电容成一个单位。The L-match network essentially borrows some of the capacitance from the tank capacitor to perform the matching operation, thus leaving the tank circuit to resonate at a higher frequency. 向人借钱的L-match网络的本质上的一些电容从内胆电容器进行匹配操作,因此剩下坦克电路产生共振频率较高的一个。For this reason the matching inductor is usually fixed or adjusted in coarse steps to suit the intended workpiece to be heated, rather than provide the user with a fully adjustable power setting.因为这个原因匹配电感通常是固定或调整以适应在粗糙的步骤预期工件进行加热,而不是为用户提供了一个全功率可调设置。
 
5. 5。Impedance matching transformer.阻抗匹配变压器。
The power supplied by the inverter to the work coil can be varied in coarse steps by using a tapped RF power transformer to perform impedance conversion. 逆变电源供给的工作卷在粗糙的步骤可以变换用拍了射频电力变压器进行阻抗转换。Although most of the benefit of the LCLR arrangement is in the elimination of a bulky and expensive ferrite power transformer, it can cater for large changes in system parameters in a way that is not frequency dependent. 虽然大多数的效益进行了分析,LCLR安排在消除铁素体笨重又昂贵的电源变压器,它能迎合系统参数大的变化,在某种意义上来说,就是不频率依存的。The ferrite power transformer can also provide electrical isolation as well as performing impedance transformation duty to set the power throughput.铁素体也可以提供电力变压器电隔离阻抗变革以及履行责任能力的吞吐量。
Additionally if the ferrite power transformer is placed between the inverter's output and the input to the L-match circuit its design constraints are relaxed in many ways. 加之,如果铁素体安置在电力变压器逆变器的输入和输出L-match电路设计的限制是轻松的在很多方面。Firstly, locating the transformer in this position means that the impedances at both windings are relatively high. i.e. voltages are high and currents are comparitively small. 首先,定位变压器在这个职位上,意味着阻抗都是相对high.即绕组电流是呈高电压comparitively小。It is easier to design a conventional ferrite power transformer for these conditions. 这是更容易设计常规铁氧体电力变压器为这些条件。The massive circulating current in the work coil is kept out of the ferrite transformer greatly reducing cooling problems. 大量流通工作电流线圈铁素体拒之门外变压器大大减少冷却的问题。Secondly, although the transformer sees the square-wave output voltage from the inverter, it's windings carry currents that are sinusoidal. 其次,虽然变压器输出电压方波看到从逆变器,它是绕组电流正弦是进行。The lack of high frequency harmonics reduces heating in the transformer due to skin effect and proximity effect within the conductors.缺乏高频率加热降低变压器由于皮肤效果和邻近效应,在导体。
Finally the transformer design should be optimised for minimum inter-winding capacitance and good insulation at the expense of increased leakage inductance. 最后,变压器设计应优化的最低inter-winding电容和良好的保温效果费用增加的泄漏的电感。The reason for this is that any leakage inductance exhibited by a transformer located in this position merely adds to the matching inductance at the input to the L-match circuit. 其原因是,任何泄漏电感变压器所展现出位于这个职位仅仅增加了匹配电感在L-match的输入电路。Therefore leakage inductance in the transformer is not as damaging to performance as inter-winding capacitance.因此泄漏电感在变压器不伤害了性能,inter-winding电容。
 
6. 6。Phase-shift control of H-bridge.H-bridge控制相位。
When the work coil is driven by a voltage-fed full-bridge (H-bridge) inverter there is yet another method of achieving power control. 当工作线圈端由一个voltage-fed桥(H-bridge)逆变器还有另一种方法来实现电源的控制。If the switching instants of both bridge legs can be controlled independently then it opens up the possibility of controlling power throughput by adjusting the phase shift between the two bridge legs.如果交换的瞬间都可独立控制桥臂就打开了可能的吞吐量控制能力,通过调整相位变换的两个桥之间的腿。
When both bridge legs switch exactly in phase, they both output the same voltage. 当两桥臂开关完全阶段,他们都输出相同电压。This means there is no voltage across the work coil arrangement and no current flows through the work coil. 这意味着没有工作电压和电流线圈安排通过工作线圈。Conversely, when both bridge legs switch in anti-phase maximum current flows through the work coil and maximum heating is achieved. 相反地,当两桥臂最大逆相开关的电流通过工作线圈和最大的加热效率。Power levels between 0% and 100% can be achieved by varying the phase shift of the drive to one half of the bridge between 0 degrees and 180 degrees when compared to the drive of the other bridge leg.功率电平0%和100%之间,才能实现由不同的相位差的二分之一的动力,0度之间的桥梁和180度相比于驱动的一座桥腿。
This technique is highly effective as power control can be achieved at the lower power control side. 这一技术是非常有效的权力控制能达到了低功耗控制的一面。The power factor seen by the inverter always remains good because the inverter is not detuned from the resonant frequency of the work coil, therefore reactive current flow through free-wheeling diodes is minimised.被功率因数的逆变器始终如一的良好,因为逆变器,从共振频率不嗡嗡作响的工作线圈,因此无功电流流过防续流二极管。
 
Induction Heating Capacitors感应加热电容器
The requirements for capacitors used in high power induction heating are perhaps the most demanding of any type of capacitor. 电容器的要求用于高功率感应加热也许是最苛刻的任何类型的电容器。The capacitor bank used in the tank circuit of an induction heater must carry the full current that flows in the work coil for extended periods of time. 电容器银行使用了在坦克电路的感应加热要把全部的电流流过线圈工作很长时间。This current is typically many hundreds of amps at many tens or hundreds of kilohertz. 当前是典型的成百上千的电流在许多几十或几百个千赫之间。They are also exposed to repeated 100% voltage reversal at this same frequency and see the full voltage developed across the work coil. 他们也暴露在重复100%在这相同的频率电压逆转,看看完整的电压在工作了卷。The high operating frequency causes significant losses due to dielectric heating and due to skin effect in the conductors. 高的操作频率造成带来重要影响介质加热和由于在集肤效应导体。Finally stray inductance must be kept to an absolute minimum so that the capacitor appears as a lumped circuit element compared to the reasonably low inductance of the work coil it is connected to.最后电感必须保持绝对的最低,使电容器,看起来就像一个集中电路元件的合理相比,低的电感线圈工作相关。
Correct choice of dielectrics and extended foil construction techniques are used to minimise the amount of heat generated and keep effective-series-inductance to a minimum. 正确地选择扩展电介质和铝箔施工工艺是用来将产生的热量,保持effective-series-inductance降到最低。However, even with these techniques Induction heating capacitors still exhibit significant power dissipation due to the enormous RF currents they must carry. 但是即使在这些技术感应加热电容器仍然表现出明显的功耗由于巨大的射频电流他们必须携带。Therefore an important factor in their design is allowing the effective removal of heat from within the capacitor to extend the life of the dielectric.因此在他们的设计的一个重要因素,允许移热设备从内部有效延长使用寿命的电容的绝缘体。
The following manufacturers produce purpose built components:下面的制造商生产的目的建造的组成部分:
 
High Energy Corp.高能总公司。(UK distributer is AMS Technologies.)(英国distributer是自动对盘及成交系统技术。)
Vishay Components.Vishay组件。
Celem Power Capacitors.Celem电力电容器。based in Israel.位于以色列。

Range of high power induction heating capacitors from范围的高功率感应加热电容器High Energy Corp.高能总公司。

High power conduction cooled mica capacitor from高功率办理冷却云母电容器Celem Power Capacitors.Celem电力电容器。CelemCelem
(Pictures courtesy of(图由Steve Conner史蒂夫拼贴)
Note the large surface area of the connection plates on the Celem conduction-cooled components and the reactive power rating (KVAR) printed on the rating label. 注意那个大的表面积的Celem连接上的盘碟conduction-cooled部件和无功功率??名()印制KVAR,评分的标签。Higher power units pictured above in aluminium cases have connections for water cooling hoses to remove the heat generated internally.上图发电机组高铝案例已经连接软管水冷热气移除的内部。
 
LCLR network frequency responseLCLR网络频率响应
The LCLR network is a 3rd order resonant system consisting of two inductors, one capacitor and one resistor. 这LCLR网络是一个三阶谐振系统由两个电感器,一个电容和一个电阻。The bode plot below shows the way in which some of the voltages and currents within the network change as the drive frequency is altered. 这预示着阴谋的下面显示的内部网络的电流和电压变化的驱动频率的改变。The GREEN traces represent the current passing through the matching inductor, and therefore the load current seen by the inverter. 绿色的痕迹经过代表当前匹配电感,因此负荷电流被检测者看到的变频器。The RED traces represent the voltage across the tank capacitor, which is the same as the voltage across the induction heating work coil. 红色代表痕迹电压坦克一样,电容器的感应加热的电压工作线圈。The top graph shows the AC magnitudes of these two quantities, whilst the bottom graph shows the relative phase of the signals relative to the AC output voltage from the inverter.前图显示了交流重要的很少,而这两个数量相对相图显示了底部的讯号,相对于交流输出电压从变极器。

From the amplitude part of the bode plot it can be seen that maximum voltage is developed across the work coil (top red trace) at one frequency only. 从振幅的一部分情节现象可以看出,最大电压在工作了线圈上红微量)频率而已。At this frequency current through the work coil is also maximum and the largest heating effect is developed at this frequency. 在这个频率上工作电流流过线圈也是最大和最大的采暖效果不了这个频率。It can be seen that this frequency corresponds to the maximum load current drawn from the inverter (top green trace.) 可以看出,这个频率的最大负载电流与来自逆变器(顶绿色的痕迹。)It is worth noting that the magnitude of the inverter load current has a null at a frequency only slightly lower than that which gives maximum heating. 值得注意的是这逆变器的大小负载电流的频率空了,仅略低于为最大供暖。This plot shows the importance of accurate tuning in an induction heating application. 该地块显示的重要性,精确的调整感应加热的申请。For a high Q system these two frequencies are very close together. 高问体系这两个频率是非常接近。The difference between maximum power and minimum power can be only a few kilohertz.最大的区别力量和最小的能力可以只是几个千赫之间。
From the bottom graph we can see that for frequencies below the maximum power point, the work coil voltage (green) is in-phase with the output voltage from the inverter. 从底部图表我们可以看出频率最大功率点下面,工作线圈电压(绿色)是同步的输出电压从变极器。As the operating frequency increases the phase angle of the work coil voltage changes abruptly through 180 degrees (phase inversion) right at the point where maximum power is being processed. 运行频率的升高相位变化的工作线圈电压突然通过180度(即相位反转)正确,最大功率的地方被加工。The phase angle of the work coil voltage then remains shifted by 180 degrees from the inverter output voltage for all frequencies above the maximum power point.相位的工作线圈电压,然后是180度的转变对所有的频率输出电压逆变器的最大功率点以上。
From the bottom graph we can also see that the load current from the inverter exhibits not one but two abrupt phase changes as the operating frequency is progressively increased. 从底部图表我们可以看到负荷电流逆变器的展品的不是一团而是两团突兀,操作频率相位变化逐步增加。Inverter load current initially lags the inverter's output voltage by 90 degrees at low frequencies. 逆变器负载电流的逆变器的最初滞后90度后输出电压在低频率。Load current abruptly slews through 180 degrees to a phase lead of 90 degrees as the operating frequency passes through the "null frequency" of the network. 突然slews负载电流通过一个阶段180度,领先的90度操作频率经过“零的频率”网络。Inverter current remains leading by 90 degrees until the maximum power point is reached, where it again abruptly slews through 180 degrees and returns to the 90 degree lagging phase once again.逆变器电流强度保持领先90度,直到达成共识,最大功率点的地方突然又slews通过180度,回到了90度落后的阶段的一次。
When we consider that only current out of the inverter that is in-phase with the output voltage contributes to real power transfer we can see that these abrupt transitions from -90 degrees to +90 degrees clearly need a more detailed examination...只有当我们考虑其电源电流,输出电压同步,有助于真正的功率传输我们注意到这些突然转折+ 90度-90度显然需要一个更详尽的…

The bode plot above shows the area of interest around the null frequency and the maximum power point in more detail. 这预示着阴谋上面显示了感兴趣的地区在空频率和最大功率点进行更详细的讨论。It also shows a family of curves depicting the behaviour of the induction heating tank circuit with a variety of different workpieces present. 它也演示了一个家庭的曲线描述感应加热的行为坦克电路以多种不同工件的礼物。This allows us to get a feel for how the network behaves with a large lossy workpiece to having no workpiece present at all, and all loads in between.这让我们感受一下如何表现有一个很大的网络有损工件没有存在在所有工件,所有装载之间。
 
With no workpiece installed, losses are low and Q factor is high. 没有工件安装、损失都很低,问因素是高。This gives rise to the sharply peaking currents and voltages in the top graph, and the abruptly changing phase shifts in the bottom graph. 这大大增加了急剧率电流、伏特的上图中突然改变,并在底部相移图。As a lossy workpiece is introduced the overall Q factor of the LCLR network falls. 介绍了作为一个有损工件的整体问因素的LCLR网络下降。This causes less resonant rise in the inverter load current and the voltage across the work coil. 这导致不少共鸣的逆变器负载电流上升和电压工作线圈。The resonant peaks become less tall, and broader as the Q factor falls. 共振峰变得不那么高,和更广阔的为问因素下降。Likewise the phase of the inverter current waveform and the work coil voltage slew less rapidly for lower Q factors.同样的相位逆变器电流波形和工作线圈电压那么快地杀了低问因素。
 
From these graphs we can deduce a few implications for any control system that must track the resonant frequency of the LCLR arrangement and control power throughput. 从这些图表我们可以推断出一些影响必须跟踪任一个控制系统的共振频率LCLR布局和控制能力的吞吐量。Firstly there is more resonant rise in the LCLR network when there is no workpiece present. 首先有更多的共振上升网络LCLR没有工件的礼物。Therefore the current delivered from the inverter should be decreased to prevent the work coil and tank capacitor currents sky-rocketing in the absence of any significant loss in the system. 因此当前脱离了逆变器应降低防止和坦克电容电流线圈工作专门在缺乏任何重大的损失的实现。Secondly, the inverter load current with no load must be tracked very accurately if the inverter is not to see either a leading or lagging load current because it slews so quickly through zero degrees.其次,逆变器工作负荷电流没有负荷必须跟踪非常准确如果逆变器并不是看到这两头部或负载电流滞后,因为它slews如此迅速地在0度。
Conversely we can say that with a large lossy workpiece present, there will be less resonant rise inherent in the LCLR arrangement and the inverter will have to supply more load current in order to achieve the required level of current in the work coil. 相反地,我们可以说,有一个很大的有损工件礼物,将有更少的共振上升LCLR固有的布置和逆变器将提供更多的负荷电流以达到所需一级工作电流线圈。However, the control electronics now do not need to track the resonant frequency so closely since the diminished Q gives a load current that shifts phase in a more leisurely manner.然而,控制电子现在不需要跟踪如此紧密的共振频率的减少以来给负载电流的Q,不断调整阶段更悠闲自得的态度。
Finally a number of points are worthy of consideration from the plot above when considering an automatic control stratergy to track the resonant frequency of an LCLR induction heater. 最后的几个点是值得考虑的情节在考虑以上的自动控制stratergy跟踪的谐振频率LCLR感应加热。For very lossy workpiece materials, (or large volumes of metal that introduce a significant overall loss) we can see that the inverter load current phase (bottom green plot) sometimes fails to ever cross through zero degrees to leading phase. 对于非常有损工件材料,(或大量的金属介绍一个重要的整体丢失),我们可以看出,逆变器负荷电流相位(下)也未能绿色情节穿过零摄氏度永远领先的阶段。This means that the inverter load current with heavy workloads cannot be in-phase and is always lagging by some amount. 这意味着逆变器与负载电流不能繁重的工作及总是落后的一些金额。Furthermore the inverter load current is not monotonic as frequency is swept. 此外逆变器工作负荷电流不随频率的单调清扫。Therefore direct feedback from a Current Transformer (CT) on the inverter output is not a viable option. 因此直接反馈从电流互感器在逆变(CT)产量不一种可行的方案。Whilst it may appear to work fine with no workpiece fitted or only moderate heating loads, it does not track the resonant frequency correctly and will fail to operate satisfactorily as the workload increases and network Q falls!虽然看起来做工精细,没有工件装配或仅有中度热负荷,它不跟踪共振频率就会不正确的操作满意工作量增加和网络问掉!(Direct feedback from inverter output current using a CT to form a free-running power oscillator results in a design which oscillates at low load but falls out of self-oscillation when the workload is increased.)(直接变频输出电流反馈使用电脑断层形成一个自由振荡电力振荡器设计的结果在振荡的却下降低负荷工作时振荡频率的增加。)
In contrast we can see that the work-coil voltage (and tank capacitor voltage) phase (bottom red plot) is monotonic with increasing frequency. 相反,我们可以看出,work-coil电压(和槽罐电容式电压)阶段(下红情节)是单调的越来越频繁。Furthermore it consistently passes through the -90 degree phase-lag point exactly at the frequency which gives maximum power regardless of how heavily the work coil is loaded. 此外,他们一致通过-90程度频率点上,确切地说是phase-lag为最大功率,不管有多么喘线圈工作载入。These two merits make the tank capacitor voltage waveform an excellent control variable.这两个优点使坦克电容电压波形具有良好的控制变量。In conclusion the inverter frequency should be controlled so as to achieve a consistent 90 degree lag between the tank capacitor voltage and the inverter output voltage in order to achieve maximum power throughput.总之进口变频应受到控制,以达到一致的90度的时间差电容式电压和坦克输出电压逆变器以达到最大限度地电力的吞吐量。We can now label some areas of interest on the bode plot diagram below.我们现在可以标签一些地区的兴趣在这预示着阴谋图表。

The white vertical line indicates the frequency at which the tank capacitor voltage (and also the work coil voltage) lag the inverter output voltage by 90 degrees. 白色垂直线表示频率的坦克电容式电压(也)工作线圈电压滞后的输出电压逆变器由90度。This is also the point where maximum voltage is developed across the work coil and maximum current flows through it. 这也是的地步了最大电压在工作和最大的电流通过线圈。The white line is where you want to be to develop the maximum possible heating effect in the workpiece. 白线是另一个想去的地方发展提供最大限度的采暖效果在工件。If we look at the inverter load current phase (bottom green plot) we can see that this is always between 0 degrees and -90 degrees when it crosses the white line no matter how abruptly or slowly it slews. 如果我们考察逆变器负荷电流相位(下)我们可以看到绿色的阴谋,这总是介于0度,-90度当它越过白线无论多么突然或慢慢地把slews。This means that the inverter always sees a load current that is either in-phase or at worst slightly lagging in power factor. 这意味着逆变器总把负载电流,要么是同步或在最坏的情况下,略滞后的功率因数。Such a situation is ideal for supporting ZVS soft-switching in the inverter and preventing free-wheel diode reverse-recovery problems.这种情况下是理想的支持零电压在逆变器,防止放大free-wheel二极管reverse-recovery问题。
Looking to the right of the white line we have the area shaded in blue labelled "Inductive Load region." 展望右边的白线我们有区域着色标为“蓝色感性负载地区。”As the operating frequency is increased above the maximum power point, the voltage across the work coil decreases and less heating effect is generated in the workpiece. 运行频率增加最大功率点以上,线圈电压降低,工作减少采暖效果不产生的工件。The inverter load current also falls and begins to lag in phase relative to the output voltage of the inverter. 变频器负载电流滞后,并开始也属于相对相位的输出电压变频器。These properties make the blue shaded region the ideal place to operate in order to achieve control over induction heating power. 这一特性使蓝色的阴影区域的理想场所和操作以达到控制感应加热的力量。By detuning the inverter drive frequency on the high-side of the maximum power point, power throughput can be reduced and the inverter always sees a lagging power factor.通过失谐变频器驱动频率与高端的最大灵能点、电力能力可以减少,逆变器总是能看到滞后的功率因数。
Conversely, to the left of the white line we have a band of frequencies labelled "Capacitive Load region." 相反的,白线的左边我们有的频率波段标为“电容负载地区。”As the operating frequency is decreased below the maximum power point, the work coil voltage also falls and less heating effect takes place. 操作频率降低的最大功率点下面,工作也属于线圈电压和更少的采暖效果发生。However, this is accompanied by the inverter load current possibly slewing to a leading phase angle when losses in the workpiece are low and Q factor is high. 然而,这是伴随着变频器负载电流的回转可能领先相位角当损失很低,问因素工件高。This is undesirable for many solid-state inverters as the leading load current causes loss of ZVS and leads to forced reverse-recovery of free-wheeling diodes incurring raised switching losses and voltage overshoots. 这是不受欢迎的许多固态变频器负载电流为主导的零电压造成损失,导致reverse-recovery身处随心所欲的被迫承担了二极体开关损耗和电压超调量。Therefore the capacitive load region is not recommended for achieving power throughput control.所以电容负载地区是不推荐用于实现电力吞吐量控制。
The vertical purple line marks the other end of the capacitive load region, where the inverter load current transitions again to lagging "Inductive" load current. 垂直紫色线的另一端标志的电容负载,那里的逆变器地区再转换负载电流的“归纳“负载电流滞后。This second Inductive region is of little interest since it does not achieve significant power throughput, and cannot be reached without passing through the potentially damaging capacitive load region anyway. 这第二个感应区域是不感兴趣的,因为他只获得强大的力量生产能力,通过离不开地区的潜在负面电容负载吧。When the LCLR network is driven from a squarewave inverter voltage there is also risk of significant current flow at a harmonic of the drive frequency. 当LCLR网络从squarewave逆变器驱动电压也有显著的风险在谐波电流驱动频率。It is marked on the diagram here merely for completeness.在这张图上为这里仅仅是为了完整性。
Note:注:The phase of the tank capacitor voltage was suggested as a control variable and discussed extensively in the plots above. 坦克的相位提出了电容式电压为控制变量,在进行了广泛的阴谋以上。This is because this voltage can be easily sensed using a high-frequency voltage transformer and provides all the necessary control information. 这是因为这个电压可以很容易地感觉到使用高频电压互感器,并提供一切必要的控制的信息。Whilst it exhibits a 90 degree phase shift relative to the inverter output voltage (which may at first appear undesirable) it is still a better control variable than trying to sense the tank capacitor current. 同时它也显示一个90度的相移相对于变频器输出电压(可能在第一次出现不良)它仍然是一种较好的控制变量,比试图感觉坦克电容电流。Although the tank capacitor current is in-phase with the inverter output this current can be many hundreds of amps making closed-core ferrite CTs impractical. 虽然坦克电容电流与变频器输出同步这电流可以成百上千的电流使closed-core铁氧体百强不切实际。Furthermore the 90 degree phase shift of the tank capacitor voltage waveform means that it's zero crossings are intentionally displaced in time away from the potentially noisy switching instants of the inverter. 另外,90度的相位差坦克电容电压波形意味着它是零十字路口故意转移时间离开造成潜在的噪音切换瞬间的变频器。This -90 degree phase shift of the voltage feedback signal can be allowed for in the design of the control electronics and is a small price to pay for the eased sensing and increased noise immunity gained.这-90程度的电压相位差允许反馈信号的设计控制电子装置和是一个小的代价,这减轻了感应和增加能消除杂音。
 
Cooling requirements冷却要求
#Add comments here about water cooling##添加注释这里大约水冷却#
 
Heating pictures加热图片







 
Waveforms波形

This shows the inverter output current waveform when driving the LCLR work coil arrangement close to its resonant frequency. 这说明变频器输出电流波形开车时LCLR线圈的工作安排接近其共振频率。This point corresponds to maximum power throughput and therefore maximum heating effect. 这一点符合最大功率吞吐量和因此最大采暖效果。Note how the inverter load current is almost a pure sinusoid.注意到逆变器负荷电流几乎是纯正弦波。
 

This shows the inverter output current waveform when driving the LCLR work coil arrangement substantially above its natural resonant frequency. 这说明变频器输出电流波形开车时LCLR线圈的工作安排要大大高于自然共振频率。This operating point gives reduced power throughput and diminished heating effect. 这个操作的刀尖能提供电力生产能力,减少减少采暖效果。At frequencies above the natural resonant frequency of the LCLR work coil arrangement the inductive reactance of the matching network dominates and the inverter's load current lags the applied voltage. 频率在自然共振频率LCLR线圈的工作安排的感应电抗引入的匹配网络占主导地位的和逆变器负载电流电压滞后。Notice the triangular load current caused by the inductive load integrating the inverter's squarewave voltage output over time.注意到当前三角形荷载作用下的感性负载引起的整合squarewave逆变器输出电压。
 

This shows the voltage across the work coil under normal operation when driven close to resonance. 这表明工作电压驱动时在正常操作线圈接近共振。Notice that the voltage waveform is a pure sinusoid in shape. 值得注意的是,基于电压波形是一个纯粹的形状。This is also true for the current waveform and minimises harmonic radiation and RF interference. 这也是为真正的电流波形和互信谐波辐射和RF干扰。In this case the voltage across the work coil is also higher than the DC bus voltage supplied to the inverter. 在这种情况下,电压线圈的工作也高于直流脉动电压逆变器提供的。Both of these properties are attributed to the high-Q factor of the induction heating tank circuit.这些属性都属于高q值因素的感应加热坦克电路。
 

This shows the output voltage from the inverter when it is mistuned to a frequency that is below the natural resonant frequency of the work coil. 这反映了逆变器的输出电压时,mistuned次数太多,低于自然的谐振频率的工作线圈。Notice the very fast rise and fall times of the squarewave accompanied by excessive voltage overshoot and ringing. 注意到非常迅速上升和下降的陪同下squarewave过度电压超调量和响了。These are all attributed to forced reverse-recovery of the MOSFET body diodes whilst enduring this undesirable operating mode. 这些都是归因于迫使场效应晶体管的reverse-recovery身体二极管而持久的这个令人不快的运行模式。(Overshoot and ringing is due to reverse recovery current spikes shock-exciting stray inductance in the inverter layout into parasitic oscillation.)(超调量和响是由于反向恢复电流峰值shock-exciting电感在逆变器布局到寄生振荡。)
 

This shows the output voltage from the inverter when it is tuned very slightly above the natural resonant frequency of the work coil. 这反映了逆变器的输出电压调整的时候非常略高于自然的谐振频率的工作线圈。Notice that the rise and fall times of the squarewave are more controlled, and there is comparatively little overshoot or ringing. 注意到上升和下降的squarewave更控制,或超调量较少响了。This is due to the Zero Voltage Switching (ZVS) which takes place when the inverter runs in this favourable operating mode.这是由于零电压开关(零电压)所发生当变频器运行在这个优惠的运行模式。
 

This shows the output voltage from the inverter when it is tuned precisely to the resonant frequency of the work coil. 这反映了逆变器的输出电压调整的时候就是谐振频率的工作线圈。Although this situation actually achieves maximum power throughput, it does not quite achieve Zero Voltage Switching of the MOSFETs. 尽管这种情况下达成这般最大功率的吞吐量,并不完全达到零电压开关的mosfet。Notice the little notches on the rising and falling edges of the voltage waveform. 注意到小切口在上升和下降电压波形的边缘。These occur because the mid-point of the bridge leg has not been fully commutated to the opposite supply rail during the dead-time before the next MOSFET turns on. 这些发生的,因为我们这座桥腿尚未完全commutated到对面的供应前dead-time轨道在下场效应晶体管导通。In practice a small amount of inductive reactance presented to the inverter helps provide the required commutating current and achieve ZVS. 在实践中少量的感应电抗引入呈现给我们的逆变器帮助提供所需的交换电流和实现零电压。For this reason the situation described for the previous photograph is preferable to being precisely in tune.因为这个原因中描述的状况比前的照片被精确调好了。