Forced commutation four-leg silicon controlled rectifier PWM (Pulse Width Modulation) soft starter and control method thereof

Abstract

The invention discloses a forced commutation four-leg silicon controlled rectifier PWM soft starter and a control method thereof, belongs to the technical field of AC-DC-AC frequency converters, and aims to solve the problem that an existing AC-DC-AC frequency converter starter has the problems of lower starting torque, more power switch devices and higher cost. The forced commutation four-leg silicon controlled rectifier PWM soft starter comprises a rectifier circuit, a filter circuit and an inverter circuit; the rectifier circuit and the inverter circuit are connected with a power source and a load respectively, the input end of the filter circuit is connected with the output end of the rectifier circuit; the output end of the filter circuit is connected with the input end of the inverter circuit and the W phase of the motor, and the output end of the inverter circuit is connected with the U phase and the V phase of the motor. A PWM signal is adopted to control the silicon controlled rectifier to carry out forced commutation, step voltage regulation and variable frequency speed regulation can be realized, the number of power switch devices is effectively reduced, the production cost is reduced, and the control performance of the soft starter is improved.

Description

technical field [0001] The invention belongs to the technical field of AC-DC-AC converters, and in particular relates to a forced commutation four-bridge thyristor PWM soft starter and a control method thereof. Background technique [0002] AC-DC-AC inverters are widely used to drive three-phase AC asynchronous motors. Generally, traditional AC-DC-AC inverters are mainly composed of rectifiers and inverters. The rectification part is diode three-phase bridge uncontrolled rectification. Such rectifiers are generally simple in structure. Reliable performance and easy maintenance. The inverter is a three-phase bridge circuit composed of IGBTs, which is widely used in the market. Since the inrush current is large when the motor is started directly, a soft starter is usually used to start it, which can also prevent the feedback current of the motor from causing an impact on the power grid. The starting torque of the traditional thyristor voltage-regulating soft starter is low, ...

AI Technical Summary

Problems solved by technology

The starting torque of the traditional thyristor voltage-regulating soft starter is low, which is difficult to apply to the on-load starting of high-power motors. There are many power switching devices when starting with traditional AC-DC-AC inverters, resulting in increased equipment volume, higher costs, and higher prices. More expensive and many other disadvantages lead to weak market competitiveness of AC-DC-AC inverters for soft start applications of high-power motors

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