Mitsumi electronic FR-F520-0.75K Inverter-driven 400V class motor, Line-to-line leakage currents

INSTALLATION AND WIRING

(2) Line-to-line leakage currents

Harmonics of leakage currents flowing in static capacities between the inverter output cables might operate the external thermal relay unnecessarily. When the wiring length is long (50m (164.04feet) or more) for the 400V class small-capacity model (7.5kW (10HP) or less), the external thermal relay is likely to operate unnecessarily because the ratio of the leakage current to the rated motor current increases.

•Line-to-Line Leakage Current Data Example (200V class)

Motor Capacity	Rated Motor	Leakage Current (mA)
		Wiring length 50m	Wiring length 100m
(kW (HP))	Current (A)
		(164.04feet)	(328.08feet)
0.4 (1/2)	1.8	310	500
0.75 (1)	3.2	340	530
1.5 (2)	5.8	370	560
2.2 (3)	8.1	400	590
3.7 (5)	12.8	440	630
5.5 (7.5)	19.4	490	680
7.5 (10)	25.6	535	725

*The leakage current of the 400V class will be approximately twice that of the 200V class.

Motor: SF-JR 4P

Carrier frequency: 14.5kHz

Cable used: 2mm2 4-core cable

NFB	Thermal relay	Motor
Power	Inverter	IM
supply
	Line static capacitances
	Line-to-Line Leakage Current Path	2

#Countermeasures

•Use the electronic overcurrent protection (Pr. 9) of the inverter.

•Decrease the carrier frequency. Note that motor noise increases. Selection of Soft-PWM (Pr. 240) will make it unoffending.

To ensure that the motor is protected against line-to-line leakage currents, it is recommended to use a temperature sensor to directly detect motor temperature.

2.3.5 Inverter-driven 400V class motor

In the PWM type inverter, a surge voltage attributable to wiring constants is generated at the motor terminals. Especially for a 400V class motor, the surge voltage may deteriorate the insulation. When the 400V class motor is driven by the inverter, consider the following measures:

•Measures

It is recommended to take either of the following measures:

(1) Rectifying the motor insulation

For the 400V class motor, use an insulation-rectified motor. Specifically,

1)Specify the “400V class inverter-driven, insulation-rectified motor”.

2)For the dedicated motor such as the constant-torque motor and low-vibration motor, use the “inverter- driven, dedicated motor”.

(2) Suppressing the surge voltage on the inverter side

On the secondary side of the inverter, connect the optional surge voltage suppression filter (FR-ASF-H).

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