I am setting up a die casting shop and I ran across a problem with the electricity. I have in particular a machine which has a 50 HP motor which starts using the Star Delta configuration. The power company told me I need to get a place that has three phase 208 volts WY3. The locations that I have found only have 240 delta 3 phase. The power company told me once the HP is over 25 HP I need the 208. With this motor that I have starting with the Star Delta option, could I use the delta 249? Will I have any problems using the 240 delta? What else can I do?

Thank you
Nicolas Gengenbach

 

Is the power provider saying that they cannot change your transformers to wye 208?

If they have 3 high voltage lines outside (5,000 volts or higher), then they can change your system to wye 208 by changing transformers.

 

For a three phase motor wired for star/delta starting, you need only a three phase supply and the neutral is not needed.
If you already have a motor with different name plate voltage other than the supply voltage, you will need an auto transformer to step up /down to the correct motor voltage (3ph/3ph auto transformer) and a small control transformer to connect your suppy to the correct control voltage.
best regards
Sekar

 

Please send additional information:

a) What is the nameplate data of the existing 50 Hp motor?

b) Is the power company saying that only a 208 volt, wye-derived source, is available?

c) What is the Hp limit on the 240 volt source you have found? The fact that it is a delta-derived source is unimportant! What is important is whether or not it is compatible with the motor's rated voltage.

d) Could the power company mean that if the Hp is over 25, then star-delta starting is mandatory?

Regards,
Phil Corso, PE
(Boca Raton, FL)