- Joined
- Oct 29, 2012
- Messages
- 1,328
Transformers connected to VFD output is possible but not advisable if I understand your application correctly.
Where I work we make subsea tools that operate at the end of a 10,000ft cable. To reduce voltage drop along that cable we use 3,000V motors. We use 480V/100A VFDs into a sine filter, into a 480>3,200V transformer. We have done it successfully with many Omron and ABB VFDs.
Off-the-shelf 60Hz Transformers have a specified reluctance (measure of magnetic "resistance") appropriate for 60Hz. When you operate below 60Hz they saturate too easily. In order to maintain variable speed with this setup, we must use special-order 30Hz transformers which are huge, heavy, and expensive. If you were to use this setup to get a fixed 60Hz, this wouldn't be a consideration.
The output of VFDs is very nasty, electrically speaking. Many spikes and much noise. The sine filter helps, but it's still gross coming out of the sine filter. The transformer acts as a second filter, but the spikes that do make it through, are amplified. If you are using the setup to power an entire 480V system, expect your electronics to see some nasty power. Sine filter is a must.
If you're doing this just for one motor, fixed 60Hz, it's feasible. But it sounds like you want to power a whole machine with it, which may include electronics, therefore I don't recommend it.
Where I work we make subsea tools that operate at the end of a 10,000ft cable. To reduce voltage drop along that cable we use 3,000V motors. We use 480V/100A VFDs into a sine filter, into a 480>3,200V transformer. We have done it successfully with many Omron and ABB VFDs.
Off-the-shelf 60Hz Transformers have a specified reluctance (measure of magnetic "resistance") appropriate for 60Hz. When you operate below 60Hz they saturate too easily. In order to maintain variable speed with this setup, we must use special-order 30Hz transformers which are huge, heavy, and expensive. If you were to use this setup to get a fixed 60Hz, this wouldn't be a consideration.
The output of VFDs is very nasty, electrically speaking. Many spikes and much noise. The sine filter helps, but it's still gross coming out of the sine filter. The transformer acts as a second filter, but the spikes that do make it through, are amplified. If you are using the setup to power an entire 480V system, expect your electronics to see some nasty power. Sine filter is a must.
If you're doing this just for one motor, fixed 60Hz, it's feasible. But it sounds like you want to power a whole machine with it, which may include electronics, therefore I don't recommend it.