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maverick83pk
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Join Date: Jul 2010
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Identify if a 3 ph Motor is Designed for Star or for Delta

07/06/2010 2:08 PM

My question is how can one identify if a motor is designed for star or for delta connection reading the name plate only?
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JRaef
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#1

Re: Identify if a 3 ph Motor is Designed for Star or for Delta

07/06/2010 2:37 PM

You don't really need to know. If your voltage matches the voltage on the nameplate, connect it for the voltage you have. The internal connection used by the motor mfr. is irrelevant. If it is a dual voltage motor it sort of matters, but again, you only need to worry about connecting to the pattern that matches what you have.

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maverick83pk
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#2
In reply to #1

Re: Identify if a 3 ph Motor is Designed for Star or for Delta

07/06/2010 3:08 PM

thanks for the prompt reply Mr. JRaef, but how will i know what voltage i have?

my 3 phase breaker has three terminals coming out, when i measure the voltage between any two terminals with multimeter it comes out to be 440 v. My guess wud be the star connection which is available in the motor's connection box by default is suitable for the power supply system that i have.

am i right?

the second question which is a bit off the topic is my 5.5HP motor has FLA of 8.8 amp. what current should my motor draw to be in safe limits when i connect load with it?
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msamad
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#3
In reply to #2

Re: Identify if a 3 ph Motor is Designed for Star or for Delta

07/06/2010 3:44 PM

The answer to the original question is YES, it can be found from the motor nameplate but it also can be found from the motor data sheet or terminal connection detail diagram from the vendor. The nameplate (or other document) may or may not have this information. Sometimes, the information may be found in the motor terminal connection diagram in the nameplate. If the motor is designed for dual voltage (one for delta and another for star, example 400∆/690Y), then the nameplate should have the information about which voltage to be applied for what type of connections. In this case, the motor has to be connected in delta for lower voltage and star for the higher voltage.

If the motor name plate doesn't have the connection information, as already mentioned by JRaef, you don't need to worry about. Apply the name plate voltage (plus/minus 10% range) to the motor terminal and the motor should be ok.

You have 3 phase 440V supply available. If the motor nameplate indicates it is 460V motor, you can connect it to the motor and run it with applicable motor protection and voltage drop in consideration.

The motor name plate FLA is 8.8A, so the maximum current the motor should draw is 8.8A during motor run time, generally the current should remain below 8.8A most of the time.

- MS

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kvsridhar
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#4

Re: Identify if a 3 ph Motor is Designed for Star or for Delta

07/06/2010 10:08 PM

If all six leads of the motor winding are brought out to terminals, as is usually the case here in India for >10 kW/15HP, the motor is designed to run in delta, with the option of starting in star, using a ΥΔ starter, to prevent disturbances to the line. If you have your own power plant and line disturbance is immaterial, you can connect the motor in delta and start DOL if you so wish.

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PWSlack
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#5

Re: Identify if a 3 ph Motor is Designed for Star or for Delta

07/08/2010 3:26 AM

If in doubt, consult a qualified electrician.

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