cheap drive

[RETRAINDAILY]

I have a Control panel that is marked at 5k because of 3 drives that are in it.

and I'm at 35k.

What are the options?
isolation transformer?
a reactor ?
a current limiting device?






or change the drives?

what is this ?
FPN: Equipment intended to interrupt current at other than fault levels?

 

[mcclary's electrical]

I have a Control panel that is marked at 5k because of 3 drives that are in it.

and I'm at 35k.

What are the options?


isolation transformer?
a reactor ?
a current limiting device?




or change the drives?

what is this ?
FPN: Equipment intended to interrupt current at other than fault levels?

I f I'm understanding you correctly, your available fault current is highter than your drives are rated for? Where did those numbers come from? I find it hard to believe that you fault current is that high at a remote distribution panel. Did the POCO give you those numbers?

 

[RETRAINDAILY]

I f I'm understanding you correctly, your available fault current is highter than your drives are rated for? Where did those numbers come from? I find it hard to believe that you fault current is that high at a remote distribution panel. Did the POCO give you those numbers?

no POCO gave us 65k at the service
then we set a 1200amp i line about 150' away and was still in the 40k range. now a new piece of equipment is 10k SCCR about 100' from there.

last time it took 400' to get down to 8k and that was out of a 800amp panel that is 250' from the service.

so I assume we will still be in the 30k range at the new control panel

I called my EE guy he will be there tomorrow.

The factory guys are ready to buy a isolation transformer today.witch is fine by me I know were to get those :roll:

but would like to have some knowledge of the facts and options before I go and say things I shouldn't

 

[mcclary's electrical]

no POCO gave us 65k at the service
then we set a 1200amp i line about 150' away and was still in the 40k range. now a new piece of equipment is 10k SCCR about 100' from there.

last time it took 400' to get down to 8k and that was out of a 800amp panel that is 250' from the service.

so I assume we will still be in the 30k range at the new control panel

I called my EE guy he will be there tomorrow.

The factory guys are ready to buy a isolation transformer today.witch is fine by me I know were to get those :roll:

but would like to have some knowledge of the facts and options before I go and say things I shouldn't

IMO, you already have a grip on the situation. Once you get hard numbers from your engineer, you'll konw what you have to do. Although others hear might have different options, you have a good plan

 

[kingpb]

Based on a lot of assumptions, I come up with 8kA, 100' away from the 1200A switchboard.

Assumptions are:

480V and no transformers involved.

65kA is at the LV side of the utility service, again no transformers involved.

100' of cable to the control panel is installed in metal conduit, above grade, size #4AWG THWN, i.e. 100 A.

You can reduce fault current by simply adding reactance in the line ahead of the drive/panel.

A few options, some not very practical.

1. Take a long route from source to load, i.e. lots of cable.
2. You could use a whole bunch of cable coiled up at the load, not very practical, but in a pinch it works.
3. Add a line reactor, they are essentially a big short circuit choke but can hurt voltage regulation of the supply voltage to your load. If that is concern, then watch out for that.
4. A transformer with the right impedance would also work, i.e. isolation transformer with a one-one voltage ratio. But that will do essentially the same thing as a line reactor, and probably be more expensive.
5. If you can reduce load requirement to 80 Amps at the control panel, or less, I think you can get to the 5KA by using #6 or smaller cable.

 

[LarryFine]

Wouldn't current-limiting fuses help?