500-KW VFD Motor and Ordinary Cable

Hello Samir Saha

VFD Motors can be run without shielded cable, but read the cautions below please.

A VFD running a 500kW motor would be best to have the motor cable shielded.

Even motors as small as 5kW on a VFD, and using unshielded cable to the motor have been known to cause radiated interference with other nearby electronic equipment, and there has been caused more than one factory accident from that very cause.

Please note that some Makers state that their VFD equipment does not cause any harmonics, but in practice this is not entirely true.

The reason is to prevent high order harmonics from being radiated to other electronic equipment from an unshielded cable on a larger motor as you intend.

Most electronic equipment is screened and filtered against such radiated harmonics, but for the very practical reasons of personnel and equipment safety, the small extra cost of shielding the motor cable will ensure that there is no interference.

Kind Regards....

Hello,

for temporary usage is ok but should not place cable next by electronic devices

The size of cable seems smaller than the power. be careful with fire risk.

Regards

Hello dbt

I did note that the Topic Question did not list the motor voltage.

The cable may well be cross-linked polythene cable, or other high-temperature cable.

It may also be that the motor voltage is 3-Phase 660 Volt, 1.1kv or 3.3kV, since we have yet to be advised by Samir Saha.

Kind Regards....

I would like to add that i would prefer the neutral to be of same size as main due to harmonics

Friend,

For this application, I believe the fourth conductor is a ground (earthing) conductor, so its reduced size is acceptable. I would agree with you, if it were a neutral.

--JMM

If it is not practical to to use shielded motor cables, adding a passive harmonic filter directly on the output of the VFD could be your solution.

Samir Saha,

In my experience, many times you can do without a shelded (screened) motor cable. However, it will be radiating electronic noise. Pay very close attention to the manufacturer's instructions regarding this as well as where to connect the ground (earthing) conductor. Failure to exactly follow their instructions is a code violation and can create more serious noise problems also. I have seen equipment malfunction because of improper ground connections as well as from induced noise on 4-20mA current loops from non-shielded VFD motor cables.

Regards--JMM