How to Reduce the Damage of Inverter to Motor

The inverter will cause a certain degree of damage to the motor, the current commonly used motor protection methods are the following four:

1) Install reactors at the output of the inverter: This measure is the most commonly used, but it should be noted that this method has a certain effect on shorter cables (below 30 meters), but sometimes the effect is not ideal.

2) Install dv/dt filter at the output of the inverter: This measure is suitable for occasions where the cable length is less than 300 meters, and the price is slightly higher than the reactor, but the effect has been significantly improved.

3) Install a sine wave filter at the output of the inverter: This measure is ideal. Because here, the PWM pulse voltage is changed into a sine wave voltage, the motor works under the same conditions as the power frequency voltage, and the problem of spike voltage is completely solved (no matter how long the cable is, there will be no spike voltage).

4) Install the spike voltage absorber at the position of the cable and the motor interface: The disadvantage of the previous measures is that when the power of the motor is large, the reactor or filter is large in size and weight, and the price is high. In addition, the reactor and The filter will cause a certain voltage drop, which will affect the output torque of the motor. The use of the inverter spike voltage absorber can overcome these shortcomings. The SVA spike voltage absorber developed by the 706 of the Second Academy of Aerospace Science and Industry Group adopts advanced power electronics technology and intelligent control technology, which is an ideal equipment to solve motor damage. In addition, the SVA spike absorber can also protect the motor bearings.

The spike voltage absorber is a new type of motor protection device, which is connected in parallel to the power input terminal of the motor.

Its working process is as follows:

1) The spike voltage detection circuit detects the voltage amplitude on the motor power line in real time;

2) When the amplitude of the detected voltage exceeds the set threshold, control the peak energy buffer circuit to absorb the energy of the peak voltage;

3) When the energy of the peak voltage is full of the peak energy buffer, the peak energy absorption control valve is opened, so that the peak energy in the buffer is discharged to the peak energy absorber, and the electric energy is converted into heat energy;

4) The temperature monitor monitors the temperature of the peak energy absorber. When the temperature is too high, close the peak energy absorption control valve appropriately to reduce the energy absorption (under the premise of ensuring that the motor is protected) and avoid the peak voltage absorber from overheating and damage;

5) The function of the bearing current absorption circuit is to absorb the bearing current and protect the motor bearing.

Compared with the aforementioned du/dt filter, sine wave filter and other motor protection methods, the biggest advantage of the spike absorber is that it is small in size, low in price, and easy to install (parallel installation). Especially in the case of high power, the advantages of the peak absorber in terms of price, volume and weight are very prominent. In addition, because it is installed in parallel, there will be no voltage drop, and du/dt filter and sine wave!