APX A: Optional Accessories | VFD-VJ
Apx A-19
Saddle on one end
Figure 2
The length of motor cable
When motor is driven by a hybrid drive of PWM type, the motor terminals will experience surge voltages
easily due to components conversion of hybrid 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 hybrid drive
The length of the cable between hybrid drive and motor should be as short as possible (10 to 20 m or
less)
For models 7.5hp and above:
Insulation level of motor 1000V 1300V 1600V
460V
AC
input voltage 66 ft (20m) 328 ft (100m) 1312 ft (400m)
230V
AC
input voltage 1312 ft (400m) 1312 ft (400m) 1312 ft (400m)
NOTE
Never connect phase lead capacitors or surge absorbers to the output terminals of the hybrid drive.
If the length is too long, the stray capacitance between cables will increase and may cause leakage
current. It will activate the protection of over current, increase leakage current or not insure the
correction of current display. The worst case is that hybrid drive may damage.
If more than one motor is connected to the hybrid drive, the total wiring length is the sum of the wiring
length from hybrid drive to each motor.
For the 460V series hybrid drive, when an overload relay is installed between the drive and the motor
to protect motor from overheating, the connecting cable must be shorter than 50m. However, an
overload relay malfunction may still occur. To prevent the malfunction, install an output reactor
(optional) to the drive or lower the carrier frequency setting (Pr.00-17).
NOTE
When a thermal O/L relay protected by motor is used between hybrid 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. 00-17 PWM carrier
frequency).
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