Drive isolation transfomer?

[mbrooke]

How is a drive isolation transformer different from a standard off the shelf unit for power and light? Can a drive isolation transformer of the same KVA replace a failed general service unit serving only panel boards with basic lighting and utilization equipment?

 

[petersonra]

Drive isolation transformers are made to handle more harmonics and usually are better shielded.

I see no reason why they could not be used as a GP transformer.

 

[Jraef]

Drive isolation transformers are made to handle more harmonics and usually are better shielded.

I see no reason why they could not be used as a GP transformer.

Yes, just not the other way around.

Also, drive isolation transformers are available with 1:1 ratios, ie 480 primary, 480/277Y secondary. There would be little to no need for that in the GP transformer world. Lastly, drive isolation transformers are often available in sizes to match typical motor HP ranges, not the same standard kVA ranges that GP transformers come in. That helps with throughput efficiency of the drive system by not having to grossly oversize the transformer.

 

[Besoeker]

How is a drive isolation transformer different from a standard off the shelf unit for power and light? Can a drive isolation transformer of the same KVA replace a failed general service unit serving only panel boards with basic lighting and utilization equipment?

Why use one in the first place?

 

[SceneryDriver]

Why use one in the first place?

Many VFD's do NOT like corner grounded services. They don't like ungrounded services even MORE. A drive isolation transformer allows you to derive a wye-connected solid earth reference that the drive needs. Many VFD's have MOV-based surge protectors wired in a star configuration, from each incoming phase to ground. Without the isolation transformer, the MOV's try to become the star point for the whole power supply. The technical term for that is usually "fire."


SceneryDriver

 

[Jraef]

Many VFD's do NOT like corner grounded services. They don't like ungrounded services even MORE. A drive isolation transformer allows you to derive a wye-connected solid earth reference that the drive needs. Many VFD's have MOV-based surge protectors wired in a star configuration, from each incoming phase to ground. Without the isolation transformer, the MOV's try to become the star point for the whole power supply. The technical term for that is usually "fire."


SceneryDriver

Something you likely don't have to deal with I'd venture, Besoeker.

 

[mbrooke]

Yes, just not the other way around.

Also, drive isolation transformers are available with 1:1 ratios, ie 480 primary, 480/277Y secondary. There would be little to no need for that in the GP transformer world. Lastly, drive isolation transformers are often available in sizes to match typical motor HP ranges, not the same standard kVA ranges that GP transformers come in. That helps with throughput efficiency of the drive system by not having to grossly oversize the transformer.

Elaborate:dunce:. Since these are built for motors, what is their true KVA for resistive loads? Also these are less likely to be shielded?

Why use one in the first place?

:lol: Good question. This is a fairly new free hold over, while a general purpose unit would have to ordered brand new.

 

[GoldDigger]

I thought that because the only limiting factors in transformers are saturation and resistive heating, would not the VA rating be pretty much independent of power factor?
For a generator the PF matters because the prime mover must be able to deliver the real energy.

 

[Besoeker]

Something you likely don't have to deal with I'd venture, Besoeker.

On some occasions but where the the purpose is to change the voltage or provide 12-pulse operation.
And I've done the odd drive with a polygonal transformer to provide a phase shift from other previously installed drives.

But you're right. We don't have the plethora of different distribution systems you have to suffer from....

 

[mbrooke]

On some occasions but where the the purpose is to change the voltage or provide 12-pulse operation.
And I've done the odd drive with a polygonal transformer to provide a phase shift from other previously installed drives.

But you're right. We don't have the plethora of different distribution systems you have to suffer from....

:lol: Nor is something as simple as installing a commercial coffee maker a bummer. Get this, 3500 watt espresso machine. 2 wire 208 volts plus ground right? Bzzzztttt wrong. Turns out the stupid water valve is 120 volts. So it needs a neutral in addition to two hots and a ground :roll: :rant:

 

[markstg]

Also, drive isolation transformers are available with 1:1 ratios, ie 480 primary, 480/277Y secondary. There would be little to no need for that in the GP transformer world.

Unless your system is resistance grounded, then there is big need for them.

 

[markstg]

Also, drive isolation transformers are available with 1:1 ratios, ie 480 primary, 480/277Y secondary. There would be little to no need for that in the GP transformer world.

Unless your system is resistance grounded, then there is big need for them.

 

[Jraef]

Unless your system is resistance grounded, then there is big need for them.

For what?

 

[mbrooke]

So its safe to assume that say a 75kva drive isolation unit will be able to handle a 75kva max resistive load?