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Can the motor protector be installed in front of the inverter?
★The single-phase and three-phase AC power supply on the input side of the inverter is best not to use electrical components such as electromagnetic switches or AC contactors. Because the inverter is running with load, or the power supply line is unstable, the surge current generated by the action of the electromagnetic switch and the AC contactor will cause the overcurrent protection circuit of the inverter to operate.
Because of this, the motor protector can be used as an infrequently operated circuit breaker that can be connected to the input circuit of the inverter.
However, when choosing a protector with this structure, it should be noted that although the inverter has over-voltage, over-current and short-circuit protection, etc., the motor protector must be selected according to the rated output power of the inverter when it is used as the input of the inverter. It is best to adjust the rated current of the protector to the maximum value. When selecting a suitable motor, the frequency converter can implement thermal protection for the motor. If the motor does not match the rated capacity of the inverter, it is necessary to adjust the protection value inside the inverter or take other protective measures to ensure the safe operation of the motor. A simple understanding is that the protector is connected to the input side of the inverter, which is used as a circuit breaker.
★Take the NS2 series of motor protectors as an example, it is suitable for AC motor starters, and is suitable for circuits with AC voltage up to 690 V and current up to 80A, as overload, phase failure and short circuit protection for three-phase squirrel cage asynchronous motor It can be used for distribution line protection and infrequent load switching, and it can also be used as an isolator.
★In addition, you must pay attention when wiring. The input terminals of the inverter are generally marked with R, S, and T, while the output terminals of the inverter are marked with the words U, V, and W. It is strictly forbidden to reverse the input side and output side.
In addition, there is a leakage current in the inverter itself. In order to ensure safety, the inverter and the motor must be grounded safely. The grounding wire (PE) generally has a copper core wire with a diameter of 3.5mm2 or more, and the grounding resistance is less than 10Ω.