DC drives - a practical application of thyristors

摘要

The basic function of a dc drive is to draw electrical energy from the mains and supply electrical energy to the dc motor at whatever voltage or current is necessary to obtain the desired mechanical output. A block diagram of a simple dc drive is shown in Figure 1. There are two distinct parts to the drive: the control and firing stage and the power stage. The control stage can receive digital and analogue signals from the control panel, connection ports and communication links. It determines the speed or torque of the motor and varies the firing angle of the thyristors in the power stage. The power stage is responsible for the conversion of the mains supply to a dc voltage and the power flow to the motor. This is accomplished by using a three-phase bridge, which typically consists of six diodes (Figure 2).