Mitsumi electronic 55K Leakage currents and countermeasures, To-ground leakage currents

INSTALLATION AND WIRING

#Example of counter measures against noise

Reduce carrier

Control box frequency.

Install filter (FR-BLF,FR-

BSF01) to inverter input side.

Inverter power	FR-	Inverter	FR-
	BLF		BLF
supply

Install filter (FR-BLF,FR-BSF01) to inverter output side.

Motor

Install filter FR-BIF to inverter input side.

Separate inverter and power line 30cm (11.81inches) or more (at least 10cm (3.94inches)) from sensor circuit.

Control power supply

Do not ground control box directly.

Stop earthing the control cable.

FR-	Use 4-core cable for motor
BIF	power cable and use one
	cable as ground cable.

Use twisted pair shielded cable. Sensor

Power supply for sensor

Do not ground shield but connect it to signal common cable.

2.3.4 Leakage currents and countermeasures

Due to the static capacitance existing in the inverter I/O wiring and motor, leakage currents flow through them. Since their values depend on the static capacitance, carrier frequency, etc. take counter measures using the following methods.

(1) To-ground leakage currents

Leakage currents may flow not only into the inverter's own line but also into the other line through the ground cable, etc. These leakage currents may operate earth leakage circuit breakers and earth leakage relays unnecessarily.

#Countermeasures

•Decrease the carrier frequency (Pr. 72) of the inverter.

Note that motor noise increases. Selection of Soft-PWM (Pr. 240) will make it unoffending.

•By using earth leakage circuit breakers designed for harmonics and surge suppression (e.g. Mitsubishi's Progressive Super Series) in the inverter's own line and other line, operation can be performed with the carrier frequency kept high (with low noise).

#To-ground leakage current

•Note that a long wiring length will increase leakage currents. Decrease the carrier frequency of the inverter to reduce leakage currents.

•Higher motor capacity leads to larger leakage currents. Larger leakage currents occur in 400V class than in 200V class.

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