VFD cable install?

NetNathan · Oct 22, 2021

I have a VFD rated for 125HP at 480V. After the VFD, there is a sine wave filter, then a 480/240 150KVA transformer, before the 100HP motor running at 240V.
Is VFD cable required here, and if so... how should the shields be grounded, or wired, at each device?

thingstodo · Oct 22, 2021

NetNathan said:
I have a VFD rated for 125HP at 480V. After the VFD, there is a sine wave filter, then a 480/240 150KVA transformer, before the 100HP motor running at 240V.
Is VFD cable required here, and if so... how should the shields be grounded, or wired, at each device?

VFD cable is important in long cable runs (if you want wireless stuff to work properly anywhere near it!). For short runs (particularly if the cable does not exit the VFD enclosure) I would not bother with the expense and the problems training the electricians in terminating the extra 2 grounds and the shield.

After the sine wave filter you *FOR SURE* don't need VFD cable.

100 HP at 240VAC? That works out to .. . around 300 amps? I don't think I've seen a transformer that size inside a panel.

NetNathan · Oct 22, 2021

thingstodo said:
VFD cable is important in long cable runs (if you want wireless stuff to work properly anywhere near it!). For short runs (particularly if the cable does not exit the VFD enclosure) I would not bother with the expense and the problems training the electricians in terminating the extra 2 grounds and the shield.

After the sine wave filter you *FOR SURE* don't need VFD cable.

100 HP at 240VAC? That works out to .. . around 300 amps? I don't think I've seen a transformer that size inside a panel.

it is an external transformer. I have to run the motor at 240V due to NFPA 86 (Standard for ovens and furnaces) because it is enclosed in an Argon atmosphere.
Is is a big cost savings to run the VFD on the 480V primary side of the transformer.

Saffa · Oct 22, 2021

Between the drive and the sinus filter, definitely. After that, no need.

NetNathan · Oct 22, 2021

Saffa said:
Between the drive and the sinus filter, definitely. After that, no need.

The sine wave filter is only about 18" from the drive. In the same enclosure.

rupej · Oct 22, 2021

I've never heard of running a drive output through a transformer. Have you done that before? I was curious if low frequencies would cause issues. Or is it effectively the same effect as a load reactor?

Saffa · Oct 22, 2021

NetNathan said:
The sine wave filter is only about 18" from the drive. In the same enclosure.

Ah sorry, I missed this fact. If your control cables are shielded, and separately run away from the power cable then all good.

Ventilation is probably your most important consideration, those sinus filters generate some substantial heat.

thingstodo · Oct 22, 2021

rupej said:
I've never heard of running a drive output through a transformer. Have you done that before? I was curious if low frequencies would cause issues. Or is it effectively the same effect as a load reactor?

After the sine wave filter, the high frequencies are almost gone. The transformer does it's thing ... lower voltage higher current ...

We had a different setup for a test. A 600 HP low voltage VFD fed to a step-up transformer that ran a 5 KV motor. I was surprised ... but it worked well, at least for the 3 month test.

NetNathan · Oct 23, 2021

rupej said:
I've never heard of running a drive output through a transformer. Have you done that before? I was curious if low frequencies would cause issues. Or is it effectively the same effect as a load reactor?

Used many times, but have been curious if i should be using shielded VFD output cables in this use. I did not really think so, just wanted views.
I have actually started using more 480V motors (inductive wound) and not the sine wave filter and stepdown transformer. In those instances, yes I am using shielded VFD motor cable.

Saffa said:
Ah sorry, I missed this fact. If your control cables are shielded, and separately run away from the power cable then all good.

Ventilation is probably your most important consideration, those sinus filters generate some substantial heat.

As far as shielding, I was only referring to if I really needed to use shielded VFD output cables. Control is Profinet.
Yes, the enclosure is well ventilated.

VFD cable install?

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