CONTACTORS FOR AC MOTOR CENTER TEST

[petronila]

Dear All,

We want to design an AC Motor Center Test For a small electric motor repair shop.To perform No load test.
Today They have a 3 Phase, 112.5 KVA 13.2 KV/ 220V distribution transformer Exclusive for feed the test center, and one 3 Phase Low Voltage 112.5 KVA transformer with this features : Primary Volts 220 and a multi tap secundary Winding : 80-150-230-380-460 Volts, any of this winding taps can handle the 112,5 KVA. 60 Hz.

The Main Idea is Use a PLC to control the contactors and the Test center will operate applying first the 80 Volts and then secuencially the other Voltages Up to 230 or 380 or 460 Volts. The test center only will test one motor at time , no test simultanelly.

How calculate the Contactors?? What protective device did you use?? Any other Design Ideas??

Thanks for the Inputs.

Petronila

 

[ScottyUK]

Contactors and thermal overloads are rated based on current. Choose them according to the current they will switch. Or have I misunderstood the question?


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Sometimes I only open my mouth to swap feet...

 

[edison123]

petronila

How about using a 0-220 V stepless, variac feeding into a 220 / 460 V testing trafo ? This way you get any voltage from 0 - 460 V without any switching / tap changing contactors ?

Of course, if the shop has 400 V supply, then can just use a 0-460 V stepless, variac ?

*Why make the same mistake twice when there so many new ones available*

 

[waross]

The contactors should be sized for the largest motors that will be tested.
respectfully

 

[jraef]

If you want just one common contactor that switches whatever you connect to it at whatever voltage you are testing with, size the contactor for the largest motor AND the current at the lowest voltage that it will see.

As far as protection devices, if you want just one prootective device do work on anything, use something solid state that can be easilly reprogrammed for the expected current.

JRaef.com
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[powerjunx]

Petronila, in our workshop we simply uses contactor which has the highest possible ampere machine rating that could put into test usually for general purpose motors. Other test set up, we uses simple primary liquid resitor.