Overcurrent protection method and overcurrent protection device for motor driver

Abstract

The invention discloses an overcurrent protection method and an overcurrent protection device for a motor driver, which can prevent damages imposed on a driver and a motor by overcurrent. The method comprises the steps of acquiring an input current peak value of a bridge rectifier and a three-phase current peak value of the motor; judging an interval where the input current peak value of the bridge rectifier or the three-phase current peak value of the motor is currently located according to the input current peak value of the bridge rectifier and the three-phase current peak value of the motor; keeping the current target frequency to be unchanged if the input current peak value of the bridge rectifier or the three-phase current peak value of the motor is located in a first interval; controlling the current target frequency to be reduced to first safe frequency or controlling the input current peak value of the bridge rectifier or the three-phase current peak value of the motor to withdraw from the second interval if the input current peak value of the bridge rectifier or the three-phase current peak value of the motor is located at a second interval; and using second safe frequency as the current target frequency if the input current peak value of the bridge rectifier or the three-phase current peak value of the motor is located at a third interval.

Description

technical field [0001] The invention relates to the technical field of motors, in particular to an overcurrent protection method and device for a motor driver. Background technique [0002] With the improvement of consumers' energy-saving requirements for electromechanical products, variable frequency motor drives with higher efficiency have been more and more widely used. However, the inverter circuit in the variable frequency motor driver is easily affected by the AC power supply, and the instantaneous change of the input voltage is relatively large. Therefore, it is necessary to equip an electrolytic capacitor with a large capacitance to reduce the impact of the instantaneous change of the voltage. However, an electrolytic capacitor with a larger capacitance has a larger volume, which increases the volume of the driver and increases the cost. In addition, electrolytic capacitors have a limited lifespan, and their effective working time is often the bottleneck of the driv...

AI Technical Summary

Problems solved by technology

However, the inverter circuit in the variable frequency motor driver is easily affected by the AC power supply, and the input voltage has a large instantaneous change. Therefore, it is necessary to use an electrolytic capacitor with a large capacitance to reduce the impact of the instantaneous voltage change.

However, an electrolytic capacitor with a larger capacitance has a larger volume, which increases the size of the driver and increases the cost

In addition, the life of electrolytic capacitor is limited, and its effective working time is often the bottleneck of the life of the driver

[0003] In related technologies, film capacitors or ceramic capacitors with small capacitances are used to replace electrolytic capacitors with large capacitances. However, due to the small capacitance of the capacitors, the magnitude of the DC voltage will fluctuate with the cycle of the AC voltage, which will easily lead to rectification. The input current of the bridge stack and the three-phase current of the motor are too large, which will damage the motor driver or motor

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