Mitsubishi Electronics FR-S500 instruction manual Power-off and magnetic contactor MC

Main circuit terminals

1.2.6Power-off and magnetic contactor (MC)

(1) Inverter input side magnetic contactor (MC)

On the inverter's input side, it is recommended to provide an MC for the following purposes. (Refer to page 10 for selection)

1)To release the inverter from the power supply when the inverter protective function is activated or the drive becomes faulty (e.g. emergency stop operation)

2)To prevent any accident due to an automatic restart at restoration of power after an inverter stop made by a power failure

3)To rest the inverter for an extended period of time

The control power supply for inverter is always running and consumes a little power. When stopping the inverter for an extended period of time, powering off the inverter will save power slightly.

4)To separate the inverter from the power supply to ensure safe maintenance and inspection work

The inverter's input side MC is used for the above purpose, select class JEM1038- AC3 for the inverter input side current when making an emergency stop during normal operation.

REMARKS

The MC may be switched on/off to start/stop the inverter. However, since repeated inrush currents at power on will shorten the life of the converter circuit (switching life is about 100,000 times), frequent starts and stops must be avoided. Turn on/off the inverter start controlling terminals (STF, STR) to run/stop the inverter.

As shown on the right, always use the start signal (ON or OFF across terminals STF or STR-SD) to make a start or stop. (Refer to page 25)

*1. When the power supply is 400V class, install a step-down transformer.

NFB		MC
Power
supply
		T (*1)
Operation ready
OFF	ON	MC
	MC
Start/Stop
MC	Operation
		RA
OFF	RA

	R/L1		U		To
	S/L2		V
	T/L3				motor
		W
	Inverter			A
				B
RA				C
	STF(STR)
	SD

Inverter Start/Stop Circuit Example

(2) Handling of output side magnetic contactor

In principle, do not provide a magnetic contactor between the inverter and motor and switch it from off to on during operation. If it is switched on during inverter operation, a large inrush current may flow, stopping the inverter due to overcurrent shut-off. When an MC is provided for switching to the commercial power supply, for example, switch it on/off after the inverter and motor have stopped.

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