75 kva transformer Primary and Secondary feed

[hillbilly1]

How often does that happen?

Have you ever done industrial?

 

[petersonra]

Have you ever done industrial?

I have been doing industrial controls for close to 40 years. Have not had a transformer crap out on me that I can recall.

Fuses have been an issue.

 

[ActionDave]

If it's from Europe it will be 50Hz. f you want to import to USA you need to consider that - especially where motors are involved.

OP says the nameplate says 60Hz

... Nameplate says 3 x400vac, fla:83a ,60hz, supply fuse 90a, Phase: 3 phase +pe, 4 wire...

 

[Besoeker3]

OP says the nameplate says 60Hz

Apologies - I missed that. Still surprises me that it would be 400 V if it is European (Netherlands).

 

[electricbird]

Thank you for all the replies. Looks like largest motor is 2.2 hp, largest load is 1 heater : 13.3 hp. This facility does have a bigger panel, (800 amp), 2 bays over, at least 100 feet of wire away. ( Not line of sight). Talked with local inspector, he said he hadn't done transformers in a while, he was retired,( had been shaking bad, 2nd inspector to retire with this condition,??!!!), stated to talk with local tech guy from power co. to advise. So either lug kit or come from 800 amp panel. The issue of nuisance tripping sounds like a pain, 400 amp???!!! , 200 amp sounds more reasonable, there must be a middle ground on this nuisance tripping issue.

 

[topgone]

Thank you for all the replies. Looks like largest motor is 2.2 hp, largest load is 1 heater : 13.3 hp. This facility does have a bigger panel, (800 amp), 2 bays over, at least 100 feet of wire away. ( Not line of sight). Talked with local inspector, he said he hadn't done transformers in a while, he was retired,( had been shaking bad, 2nd inspector to retire with this condition,??!!!), stated to talk with local tech guy from power co. to advise. So either lug kit or come from 800 amp panel. The issue of nuisance tripping sounds like a pain, 400 amp???!!! , 200 amp sounds more reasonable, there must be a middle ground on this nuisance tripping issue.

Yep. If the primary current is 180A, then apply the maximum factor of 250%. You'll come up with 450A, methinks a 400A CB will do.

 

[jim dungar]

...there must be a middle ground on this nuisance tripping issue.

The tripping on inrush issue is dealt with by having a large enough nagnetic/instantaneous pickup point.
For many breaker styles a 300A shares the same magnetic point as a 400A.

You need to ask the transformer manufacturer for the inrush current and compare it to the breaker pickup.

 

[topgone]

The tripping on inrush issue is dealt with by having a large enough nagnetic/instantaneous pickup point.
For many breaker styles a 300A shares the same magnetic point as a 400A.

You need to ask the transformer manufacturer for the inrush current and compare it to the breaker pickup.

If you can't have the inrush data, it is best to use the transformer inrush checkpoints as suggested by Cooper Systems Fusing Manual:
25X FLA @ 0.01 sec,
12 X FLA @ 0.10 sec,
6 X FLA @ 1 sec,
3 X FLA @ 10 sec, and
2 X FLA @ 100 seconds.
Then check if the breaker TCC indicates it does not trip on those checkpoints.

 

[jim dungar]

If you can't have the inrush data, it is best to use the transformer inrush checkpoints as suggested by Cooper Systems Fusing Manual:
25X FLA @ 0.01 sec,
12 X FLA @ 0.10 sec,
6 X FLA @ 1 sec,
3 X FLA @ 10 sec, and
2 X FLA @ 100 seconds.
Then check if the breaker TCC indicates it does not trip on those checkpoints.

Those are good for MV and transformers over 300kVA, they are not as reliable for smaller dry type transformers like in the OP.