Emerging Inverter Motor Protection Common Methods
Many people found that Emerson Inverter damaged the motor. For example, in a pump factory, in the past two years, his users have often reported that the pump was damaged during the warranty period. In the past, the quality of the pump factory was very solid. After investigation, it was found that these damaged pumps were driven by the inverter.
Although the frequency converter caused the damage of the motor is getting more and more attention, but the mechanism is still not clear, let alone how to prevent. The purpose of this article is to deal with these confusions.
1) Reactors at the output of the converter: This measure is more common, but it should be noted that this method has a certain effect on shorter cables (less than 30 meters), but sometimes The effect is not ideal.
2) Install dv/dt filter at the output of the converter: This measure is suitable for cable length less than 300 meters, the price is slightly higher than the reactor, but the effect has been significantly improved, as shown in Figure 6. (d) is shown.
3) Sinusoidal filter at the output of the inverter: this measure is ideal. Since the PWM pulse voltage becomes a sinusoidal voltage here, the motor operates under the same conditions as the power frequency voltage, and the peak voltage problem is completely dealt with (the cable is long and there is no spike voltage).
4) Install a spike voltage absorber at the interface between the cable and the motor: The drawback of the above measures is that the reactor filter has a large volume and weight and a high price when the motor power is large. In addition, the use of inverter spikes, reactors and filters will incur a certain voltage drop, affecting the output torque of the motor. Peak voltage absorbers are able to suppress these defects.
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