Appendix B Accessories|VFD-S Series
B-6 Revision August 2008, SE09, SW V2.61
The length of motor cable
When motor is driven by an AC motor drive of PWM type, the motor terminals will experience surge
voltages easily due to components conversion of AC motor drive and cable capacitance. When the
motor cable is very long (especially for the 460V series), surge voltages may reduce insulation
quality. To prevent this situation, please follow the rules below:
Use a motor with enhanced insulation.
Connect an output reactor (optional) to the output terminals of the AC motor drive
The length of the cable between AC motor drive and motor should be as short as
possible (10 to 20 m or less)
For models 7.5hp/5.5kW and above:
Insulation level of motor 1000V 1300V 1600V
460VAC input voltage 66 ft (20m) 328 ft (100m) 1312 ft (400m)
230VAC input voltage 1312 ft (400m) 1312 ft (400m) 1312 ft (400m)
For models 5hp/3.7kW and less:
Insulation level of motor 1000V 1300V 1600V
460VAC input voltage 66 ft (20m) 165 ft (50m) 165 ft (50m)
230VAC input voltage 328 ft (100m) 328 ft (100m) 328 ft (100m)
NOTE
When a thermal O/L relay protected by motor is used between AC motor drive and motor, it may
malfunction (especially for 460V series), even if the length of motor cable is only 165 ft (50m) or less.
To prevent it, please use AC reactor and/or lower the carrier frequency (Pr. 02-03 PWM carrier
frequency).
NOTE
Never connect phase lead capacitors or surge absorbers to the output terminals of the AC motor
drive.
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