晶闸管调压系统中的电机转速检测新方法

对三相异步电动机实施软起动控制，必需实时地监测电机的转速变化情况，传统的电机转速测量方法采用速度传感器，提出一种无速度传感器测量三相异步电动机转速的方法。该方法利用晶闸管调压电路的工作特点，结合电动机在不对称供电情况下的运行状况，得到电动机未供电相的感应电压与电机转速之间的函数关系，在此基础上，还可进一步获得相应的感应电压与电机电流之间的对应关系曲线，该方法应用于实际的电机软起动控制器中，满足了控制器在多种电机起动方式下的控制需要。

A novel speed measuring method for induction motor in voltage

It is essential to measure the speed of three phase induction motor when it is driven by a soft starter. Speed sensor is traditionally used for speed measurement. A novel method is suggested for measuring the speed of a machine without speed sensor. According to the properties of thyristor voltage controller and the operating state of the three phase induction motor with asymmetric power supply, the relation between the motor speed and inducted voltage of one phase of the motor without power supply can be obtained, a curve showing the relative relation between the induced voltage and the motor current is given. This method has been already applied to an actual soft start controller, and different starting requirements for various machines can be successfully met.