Soft starter having bypass switch fault protection function

Abstract

The invention provides a soft starter having the bypass switch fault protection function. The soft starter comprises a microprocessor, a silicon controlled rectifier drive circuit of a bypass switch and a fault detection circuit. The silicon controlled rectifier drive circuit with the input terminal connected with the microprocessor is used for receiving a trigger signal sent out by the microprocessor; the output terminal of the silicon controlled rectifier drive circuit is connected with a 3M phase of a three-phase asynchronous motor; and the fault detection circuit with the input terminal and output terminal connected with the silicon controlled rectifier drive circuit and the microprocessor respectively is used for detecting whether a fault exists in the bypass circuit of the soft starter. After the operation of the bypass, when the number of falling or rising edges of the detection signals that are received by the microprocessor within the preset bypass detection cycle and are fromthe fault detection circuit exceeds a preset fault threshold, the fault of the bypass switch is determined. With the fault detection circuit, the closed-loop control system having the fault protection function of the bypass switch is formed to prevent an over-heating or damage risk of the silicon controlled rectifier element in the silicon controlled rectifier drive circuit.

Description

Technical field [0001] The invention relates to the fields of electronic power, automation and motor control, in particular to a soft starter with bypass switch failure protection. Background technique [0002] When a three-phase asynchronous motor is started directly, the current will usually reach 5 to 8 times or even greater, resulting in a large inrush current, causing great fluctuations in the power grid in the same system, and adversely affecting the entire transmission system and equipment . The soft starter is connected in series between the three-phase asynchronous motor and the three-phase power grid, and by triggering and driving the soft starter's thyristor, the starting current can be set and limited to realize the smooth start of the motor. [0003] In the existing soft starter, there are two ways to trigger the thyristor circuit. One is to use a pulse transformer to trigger the circuit, and the other is to use an optocoupler to trigger the anode. However, in the op...

AI Technical Summary

Problems solved by technology

However, in the existing built-in bypass soft starter, the built-in bypass switch without arc extinguishing device is used. When the bypass operation condition is met, only the closing signal is applied to the bypass switch, but the bypass switch cannot be activated. Whether it is normally closed or not is detected. Once the bypass is in the running state, if the bypass switch is unreliable or not closed, the load current will flow through the thyristor, resulting in overheating protection or failure of the thyristor.

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