3 Transformers

[Hoggedy]

Update: after further inspection and with the help of engineering we found that the secondary load current on the transformer was way under rated for its purpose.
3- 5kva single phase transformers
So 5000v ÷ 120v load voltage = 41 amps of the necessary 100 amp per line needed.
We are going to reinstall a 45kva transformer.
This way it will be 15000v per line÷120v load voltage= 125 amp of secondary current. Giving us the necessary ampacity.
It also showed why our transformer feeding one of the phases caught fire, due to an improper amount of secondary current on the single phase transformers.

Dang details get in the way of getting things done.

Yes, as stated by others the single larger transformer would be better.

How long did this setup work? Years, months, or for a few minutes after the switch was thrown?

 

[JFletcher]

too much imbalance load can overheat one portion of the "bank" if secondary overcurrent protection is well over the rating of the bank.

Rated secondary current of 15 kVA is 41.6 amps if you configure them in a 208/120 wye or 36 amps if you configure them in a 240/120 delta, you needed to reach 100 amps secondary current before even considering having the secondary device open the circuit. And of course full (balanced) rating on primary side would have been 18 amps and you needed to draw 30 amps before even considering opening a primary device.

Might want to investigate what the loads actually are before selecting a 15 kVA replacement, or at least trying to balance those loads if they are under 15 kVA.


Add: and provide proper overcurrent protection - particularly to the secondary side.

This. As it is (sounds) now, a fault on the secondary side is going to wipe the xfmr before tripping the OCPD.

Pictures of everything would help immensely.

I didnt know Gloucester had electricity now, I thought yall boys were running portable gensets for everything.

(messin with ya; welcome to the forum and good luck)

 

[JFletcher]

Update: after further inspection and with the help of engineering we found that the secondary load current on the transformer was way under rated for its purpose.
3- 5kva single phase transformers
So 5000v ÷ 120v load voltage = 41 amps of the necessary 100 amp per line needed.
We are going to reinstall a 45kva transformer.
This way it will be 15000v per line÷120v load voltage= 125 amp of secondary current. Giving us the necessary ampacity.
It also showed why our transformer feeding one of the phases caught fire, due to an improper amount of secondary current on the single phase transformers.

Over-loaded vs under-rated? You may also want to balance loads across the phases if possible/customer will pay for it.