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INSTALLATION AND WIRING
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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.
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Line-to-Line Leakage Current Data Example (200V class)
Leakage Current (mA)
Motor Capacity
(kW (HP))
Rated Motor
Current (A)
Wiring length 50m
(164.04feet)
Wiring length 100m
(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
Motor: SF-JR 4P
Carrier frequency: 14.5kHz
Cable used: 2mm
2
4-core
cable
*The leakage current of the 400V class will be approximately twice that of the 200V class.
IM
NFB
Line-to-Line Leakage Current Path
Power
supply
Inverter
Thermal relay
Line static capacitances
Motor
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##
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Countermeasures
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Use the electronic overcurrent protection (Pr. 9) of the inverter.
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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:
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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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