Способ формирования мягкой механической характеристики бесконтактных двигателей постоянного тока

Abstract

A method using which it is possible to obtain a soft mechanical characteristic of contactless DC motors without transforming their power electrical circuit is considered. The motor is additionally fitted with a pulse-width modulator (PWM) and a sensor of the current consumed by the winding. The characteristic is synthesized in the form of an open polygon consisting of sections. In the PWM, the sensor output voltage proportional to the current and shaft torque is compared with a periodic sawtooth voltage, as a result of which rectangular pulses closing the switch power transistors are generated. The higher the torque and, accordingly, the higher the consumed current, the longer the pulses and the lower the mean voltage applied to the winding and the motor shaft rotation frequency. The transition from one section of the characteristic to another is done by discretely changing the parameters of the periodic sawtooth voltage in response to the current sensor signals. Joint operation of the PWM and current sensor is described, and requirements for their voltage values are formulated. Expressions for the soft mechanical characteristic are obtained. An example of calculating the soft mechanical characteristic is given.