Transformer check

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.
We hope our request receives the required attention.
Thank You,
Michael Obeng Appiah (For: Pavetech Ltd.)
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On 19 Apr 2007 09:55:58 -0700 snipped-for-privacy@gmail.com wrote:
| 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).
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|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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Hello Michael

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
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John Rye
Hadleigh IPSWICH England
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