What to know about VFD Motor Lead Lengths
Input and output power lead length should be kept as short as possible. Reflective waves can cause high voltage at the motor terminals. Depending on the lead length, there may be parameter settings and external devices needed. For longer motor lead lengths consider the below recommendations.
Carrier Frequency
•Motor cable lengths at 50 m (160 FT) or less the carrier frequency can be set up to 15kHz (with derate).
•Motor cable lengths at 100 m (330 FT) or less, require the carrier frequency to be set at 5kHz or less.
•Motor cable lengths greater than 100 m (330 FT), require the carrier frequency to be set at 2kHz or less.
•Parameter Cn/CON 4 adjusts the carrier frequency.
Most LS VFDs also have a parameter to adjust the PWM between Normal and Low Leakage – this can be adjusted in conjunction with the carrier frequency (Cn/CON 5)
Filtering
If the cable length between the motor and the drive is above 100 FT it is recommended to install a load reactor. This is due to reflected waves – as the cable length
increases, the possibility for reflected waves increases as well. Reference to the below table for filter recommendations are various lengths.