Induction Motor Taking Full Load Current at No Load in Delta Connection

Check your voltage....

http://electrical-engineering-portal.com/basics-of-3-phase-induction-motor-1

He said 380-415V delta in original post

Motor name plate reads 380-415V delta connection

Can you answer my #5? Is it OK driving the load? That's the acid test!

In most electrical motor (depend upon each country) as in my counrty, are offen design to run in delta connection at 415Vac/50hz. In delta connection, during running in NO Load condition, the running amp are usually lower than the FLC about 35% - 40% lower. This is condition is also depend upon the design of the electrical motor. By connection the Delta connection electrical motor in to the Star connection, the impendance of the motor winding will increase. The electrical motor still can be run but the motor torque are very much lower. Running the Delta connection electrical motor in to the Star connection with NO Load condition at 10 A is something not correct.

Does the motor do its job OK, under load? If so there maybe isn't a problem.

On no load the power factor is much lower, so although the amps seem high the power drawn from supply is well below motor rating

Tell me what the motor manufacturer said during the phone calls, please?

No-load 60 amp seems too much. Star 10 amp with constant impedance suggests about 30 amp delta connected, no-load, which is reasonable.

Are all phase currents the same?

Is the motor vibrating a lot or noisy on Delta?

Is it turning in the standard direction? Standard is clockwise looking on drive end, when the supply sequence is ABC at the motor terminals

Are you sure winding connections are correct - do you have the maker's connection diagram?

Phase currents are Balanced.
There is no vibration
Direction is clockwise in ABC phase sequence
We have checked with makers connection diagram, Also tested the polarity of windings.

Thanks for reply. This is very odd...............

What is the motor speed nameplate value and measured speed at frequency? If available..

This is a 4 pole 50 HZ motor & measured speed is 1492 RPM

But what are the figures when it's driving the load?

Thanks for further information. 1500 rev/min would mean more amps no-load compared to 3000 rev/min, roughly 40 amp. There is a tolerance, maybe +/- 20% on any winding impedances - that makes 48 amp. These figures for 45 kW Crompton motor at 400V. In proportion at 415V +10% = 456.5 V is 55 amp - plus there will be increased saturation.

To 55 amp can be added the probable meter error - maybe 5% or more if 60 amp is low compared to full scale. Maybe you have a CT error to add??

What meter ranges full-scale are you using, measuring 10 amp and 60 amp??

Considering the low current star connected there does not seem to be any mechanical fault.

What is actual supply voltage was there when you got 60 amp??

I think the suggestion posted that you should try the motor on-load is reasonable.

If you wish to be careful, I suggest backing-up the 60 amp reading with a different ammeter or a power factor or watts measurement.

Why do you say no-load amps would be higher on 4-pole than 2-pole? I don't get that, please explain.

My gut feeling is 1492 rpm no-load is a tad low, but I suppose could be right. My motor data says full load rpm 1475 - 1480 rpm (different makes). As you suggest, the actual supply voltage on the tests (presumably in range 380 - 415) would be of interest, as it affects slightly the rpm.

I'm not holding my breath for a reply about on-load operation ��

Further to post #20 and to be sure this is not an unusual situation.....

Are you at a high altitude above sea level? This would need derating e.g. your 45 kW motor - normally a 225 frame could be a 55 kW motor frame 250. But no-load current would increase for larger motor. The 45 kW motor data I used was frame 225

For a normal horizontal, foot mounted, motor the size "225" is the vertical distance from shaft centre to bottom of feet in millimetres.

What does the rating plate of the motor have on it?

67model

Motor is of 225 Frame.

At 30 KW input loading motor is taking 80 A which is not correct.

The measured current have no error. We have cross checked it with Clamp meter.

You have not told us the motor terminal voltage when you tested it - as noted in post #20, this has significant effect on no-load current.

Do you mean by post #23 that you have measured kW input?

If so, proper comparison with current - VA cannot be calculated without motor terminal voltage.

Since you gave 60 amp no-load current previously, may we take it 30 kW, 80 amps, ?? volts is with motor driving its intended mechanical shaft load?

Since the phase currents are the same, I am wondering if there is some odd error, like a rewind with too few turns.

I really have nothing to add, others here have not already pointed out. You have not done all your homework on this one yet. Check EVERYTHING, take nothing for granted, or nothing will turn around and bite you in the posterior.

Also check the motor bearings and couplings to make sure alignment is correct.

Usually motors 4 kW and larger 380 – 415 Volt 50 Hz are DELTA connected.

If the no-load currents in all three phases are equal it could be a wrong connection-that means it is for star winding connection made nevertheless the rating plate says other.

Since the gap is very small a small difference could change the no-load current.

It could be an air gap problem-as ball bearing damaged. In this case the currents will be unbalanced.

At a second glance the airgap is not the source of the problem.

What is confusing is the huge fraction between delta no-load current and star.

It has to be 2 about and here is 6. I think something wrong with the measurement has to be.

huge fraction =huge ration [I meant]

If you overfeed a cat for a long time, do not be surprised when it exhibits a paunch.