Transformer check

It is difficult to make any suggestions on the basis of the information that you have provided. Induction motors can easily take 5 times full load starting, so with a total of 37.5 HP on a 50 kva transformer I would expect to see very significant dips during starting.

What are the three line to neutral voltages on no load, and the three line to line voltages on no load ?

John

| Our factory is currently being fed by a dedicated 50KvA transformer | taking its source from a 33Kv line. | | We have however been experiencing voltage drops on the BLUE phase to | about levels of 150volts (with the RED and YELLOW phases at about | 220volts) when we switch on our equipment. Our total three phase motor | KW rating is about 37.5 and anytime we start up to 20KW of these | motors they cut off due to the quality of supply from the BLUE phase. | We also do not have any other loads on these phases when the motors | are on. | | We shall be grateful if you could help.

It sounds like something for your power utility to address, especially if they own/maintain the transformer(s). It could be a bad primary connection. There are many other possibilities, too.

It might help to know how the transformers are wired (D-D, D-Y, etc).