Transformer conected with a motor 2

[eduar2010]

I have a transformer conected with a motor. This transformer is connected in delta high leg in the side of low voltage.
What happens if I change the transformer to another one of equal power and voltage but connected in star in the side of low voltage

 

[waross]

It should work fine.
BUT: It may be difficult to find a transformer of the same voltage if your system is based on North American standards.
A standard delta voltage is 120:240 V delta and the corresponding wye voltage is 120:208 V wye.
However another standard is 240:480 delta and the corresponding wye voltage is 277:480 V wye.
If you go from 240 delta to 208 volt wye, your motor will not develop full torque without overheating and will not develop full starting torque. This is not an issue with many applications but if the load needs a lot of torque to start or if the load needs the full rated HP of the motor you may have issues.
Then there are 208:230 Volt rated motors and 200:230 Volt rated motors which should work fine if the original designer didn't "Push the envelope" when sizing the motor.
It depends.
What is your voltage?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

Or you can buy special transformers that will provide the same secondary voltage. If you are at 240V delta now, you can go to any electrical supply house and get a 208Y transformer very easily; you could also get a 240Y/138V transformer and wait 6-12 weeks while it is scheduled for production and then pay 2-3x what a 208Y would cost for the same rating.

 

[waross]

That works also David.
The original post begs the question;
Wye?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[petronila]

Hello Eduard

You can replace the transformer for another one with same power and voltage output, if the low voltage side is connected in star the difference is you will have a neutral point and then for a three fase system you will have single -phase voltage available, the other consideration is the neutral point could be grounded.

Regards

Carlos

 

[waross]

With the four wire delta there is a pseudo-neutral which can be used the same as a wye point neutral. It may be used for grounding or for 120 volt service. The 120:240 volt four wire delta is widely used in some areas.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[eduar2010]

The voltage is 240 volts between phases
(R to S = 240 V, R to T = 240V, S to T = 240V).
R to neutral point = 120 volts, S to neutral point = 208 volts, T to neutral point = 120 volts.
Thanks