Variable Speed Dc Motor Drives
Description: Variable speed DC motor drives consist of a simple auto-transformer rectifier control panel. In this system, variable DC voltage is obtained by rectifying continuously variable AC output voltage of an auto transformer. The AC voltage can be changed by manual rotation of auto-transformer or by push button operated pilot motor mounted on the auto-transformer. In this open loop control system, variable DC voltage supplied to the DC motor changes the speed. This simple yet reliable system is extensively used in the industry. Closed-loop auto-transformer rectifier control panel: this system combines the simplicity of auto-transformer rectifier DC drive and closed loop control used in thyristor drive. A variable DC voltage is obtained by rectifying variable AC output voltage of an auto-transformer. This system has select able open loop control and closed loop control. In open loop control, the output DC voltage can be varied by manual relation of auto-transformer or by increase/decrease push button operated pilot motor, mounted on the auto-transformer. In closed loop control, a voltage signal proportional to speed is constantly compared with a set speed reference signal, in an electronic module. Any error voltage after amplification rotates the auto-transformer automatically, to bring about the necessary correction in the DC voltage. This feature makes the drive almost uninterrupted and highly reliable. Features: stepless control of speed from zero to full rated speed at constant torque; speed regulation of better than I%; and controlled acceleration/de-acceleration to provide gradual acceleration/ de-acceleration of motor speed even if the speed setting is changed abruptly. Variable speed DC motor drives is offered by Electro Dynamic Services.
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