电动机和控制它们的电力电子之间存在微妙的平衡。这是因为功率电子器件以与绕线电感器完全不同的方式进行电。然而，他们需要设计得很好，因为这些天，几乎所有电动机技术都取决于两个组件作为电路一起运行的结果。
主要区别是浪涌电流。在交流电动机中，电流浪涌和电流承载能力是无限的，直到绕组燃烧并捕获火灾。通过电机绕组电力产生热量。电子必须对它们有某种摩擦。这就是使超导如此吸引人的原因。没有热量的电导率。但它具有成本，超导仅在低温温度下进行。因此，您必须拥有一个足够大的系统，以至于保持液体氢气温度的成本是有益的。
For power semiconductors voltage is less the issue, we have mosfets for low voltage systems and IGBT for higher voltage systems. The limitation is that power semiconductors can usually handled double their rating and no more. Also, the rate of current inrush is a slope that cannot be exceeded. These are critically different behaviors from inductors and require users to make sure that they have a good match between the current requirement for a given application.
In both systems, however, any form of thermal management can make a huge difference in the size, weight and cost of an electric motor. The size and weight of electric motorcycle power converters and motors are amazingly small, and they are all liquid cooled. The liquid cooling adds some volume and cost, but this is far less than the size and weight increase required for ambient air cooling.
Fan cooled AC motors were notorious for failure with the early variable frequency systems. The motor was designed for constant 1800 RPM operation and the fan cooling, using ambient air over the motor housing was sufficient for normal operation. If significant operating time took place at lower speed, the fan was no longer able to move enough air to keep the motor cool, leading to overheating and eventual failure of the winding.
Mis-matching of variable frequency drives to high starting loads was also a common failure in early systems. High inrush current that are acceptable to an AC motor across the line would cause power electronic failures if they were applied strictly based on the horsepower of the load.
More next week.
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