2.2 Wiring
2-9
2.2.4 Precautions for long wiring (between inverter and motor)
(1) When multiple motors are connected to one inverter, the wiring length is the total of all wire lengths.
(2) Precautions for high-frequency leakage current
Precautions shall be taken for high frequency leakage current when the wiring length from the inverter to the
motor is long, in this case the high frequency current may flow through the stray capacitance between the
wires with various phases. The effect may cause the inverter to become overheated, or trip due to overcurrent.
Leakage current may increase and the accuracy of the displayed current may not be ensured. Depending on
the conditions, excessive leakage current may damage the inverter. To avoid the above problems when
directly connecting an inverter to a motor, keep the wiring length to 50 m (164 ft) or less for FRN0018G2S-2G
/ FRN0009G2□-4G inverters or lower, and to 100 m (328 ft) or less for FRN0032G2S-2G / FRN0018G2□-
4G inverters or higher.
If using with longer wire lengths than those above, use with a carrier frequency of 5 kHz or less, and if using
a 400V series inverter, use an output circuit filter (OFL-□□□-4A) (option).
When multiple motors are operated in parallel connection configuration (group operation), and especially
when shielded cables are used for the connections, the ground to ground stray capacitance will be large. In
this case, use with a carrier frequency of 5 kHz or less, and if using a 400V series inverter, use an output
circuit filter (OFL-□□□-4A) (option).
Without output circuit filter
With output circuit filter
Below
50 m(164ft)/100 m(328ft)
When the output circuit filter is used, the total wiring length should be below 400 m (1312ft) in case of using
V/f control.
For motors with encoders, the wiring length between the inverter and motor should be below 100 m (328ft).
The restriction comes from the encoder specifications. For distances beyond 100 m (328ft), insulation
converters should be used. Please contact Fuji Electric when operating with wiring lengths beyond the upper
limit.
(3) Precautions on the surge voltage when driving the inverter (especially for 400 V series motor)
When motors are driven by inverters using the PWM method, the surge voltage generated by the switching
of the inverter elements is added to the output voltage and is applied onto the motor terminals. Especially
when the motor wiring length is long, the surge voltage can cause insulation degradation in the motor. Please
perform one of the countermeasures shown below.
∙ Use motor with insulation enhancement (Fuji’s standard motors have insulation enhancements)
∙ Connect a surge suppression unit on the motor side (SSU50/100TA-NS).
∙ Connect an output circuit filter (OFL-□□□-4A) to the inverter output side (secondary side).
∙ Reduce the wiring length from the inverter to the motor to less than 10 to 20 meters (33 to 66 ft).
(4) When an output circuit filter (OFL-□□□-4A) is inserted in the inverter, or when the wiring length is long, the
voltage applied to the motor will decrease due to the voltage drop caused by the filter or wiring. In these cases,
current oscillation and lack of torque may occur due to insufficient voltage.
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