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直流电动机拖动是用改变电枢电流和磁场电流来进行调节的。磁场电流是量度磁通的,而电枢电流和磁场电流的乘积是量度转矩的。在计算感应电动机的磁通和转矩时,也存在几种类似的方法。大多数这些方法是受电动机参数值变化的影响的,并且在接近零转速时就失效了。同样,由于逆变器输出为非正弦波,电动机电压和电流的谐波也会引起转矩计算产生误差的。在实际运转的环境下去测量感应电动机的磁通量的有效方法已经有了发展。利用磁通信号和定子电流就能得到实际的电磁转矩。这个转矩信号能正确地反映出电动机的饱和以及逆变器电压波形谐波的影响。由于可以精确地控制磁通,所以设计电动机时不必考虑通常需要的磁通裕量。使用这种反馈信号的控制方案也不需要用转速计了。
DC motor drag is to change the armature current and field current to be adjusted. The magnetic field current is a measure of flux, and the product of armature current and field current is a measure of torque. There are several similar ways of calculating the flux and torque of an induction motor. Most of these methods are affected by changes in motor parameter values and fail near zero speed. Also, because the inverter output is non-sinusoidal, harmonics of the motor voltage and current can also cause errors in the torque calculation. An effective way to measure the magnetic flux of an induction motor in a real-world environment has been developed. The use of flux signals and stator currents can be the actual electromagnetic torque. This torque signal correctly reflects the effects of motor saturation and inverter voltage waveform harmonics. Since the flux can be precisely controlled, it is not necessary to consider the flux margin typically required when designing a motor. The control scheme that uses this feedback signal also does not require a tachometer.