Wye Delta Motor Help

I have a 43Kw motor that is set up with starters to start in wye and run in delta. The motor was replaced and the new motor 43Kw is drawing twice the amperage. What am I missing? This is a 480V 3PH 60HZ motor.

Any advice. I will call the OEM in the morning, but was hoping not to lose too many more shifts of work.

Thanks in advance

Glenn

A

where do have double amp on star or on delta ..?

Why was original motor replaced?
What condition is the driven load in?
Is it possible the load is bad therefore overloading motor?
Is the motor dual voltage and is it properly hooked up?
Is motor turnin the correct direction?
What is starting current with motor and load not connected together?

Dan Bentler

Please measure current at your main CB befor wye and delta cb. If the current still double, its not so difficult to solve the problem as long your name plate motor correct to your rating.
Do manual testing for motor. Uninstall motor from load and connect motor with delta. Please make sure your connection and cable motor(these are very important cause if connection not tight or one phasa loss, this will make your current double).Test and measure current. If current still high, i think some thing wrong with your motor or wrong specification.If current normal, some things wrong with your configuration star delta.
I hope this can help you.

This may sound stupid but give it a try, move all 3 phases...ie phases are A B C make it C A B.

We had a discussion on this at the other site but I can not find it now. I will keep looking and provide more details later to explain it but try it and see if things change.

This motor is for a saw blade. The amp readings are when the motor is in delta. This is a new replacement motor and according to the nameplate is correct voltage and frequency. There is another motor with the same setup on another axis of this machine that pulls approx. half the amperage of this new motor. In the "motor terminal connection point" i.e. Pec... He.. the connection block is labeled U1 V1 W1 and V2 U2 W2. We connected according to wiring of old motor. The motor is fed through two breakers. All 6 of the leads show the same amp draw, doesn't this rule out single phasing?

What would make the motor run roughly double the amps? Wound for diffent voltage? Running in WYE, starting in Delta?

Question, is it exceeding the current rating of the motor and overloads?

2 identical motors can draw different current if load/troque is different.

The load is shared between the two feed breakers each set at 40amps. It is not tripping the breakers. There is an ampmeter on the motor circuit that tells the saw carriage to slow down travel speed or stop if the amperage is above upper threshold. Right now with the new motor not cutting any wood, just running it is just below the old motor upper threshold.

How much current is the motor pulling? Using Rons formulas it looks like 43 kw at 480 v pf 75% would be 69 amps? If it`s pulling over this with no bearing problems on the mandrel and nothing else mechanically wrong sounds like the motor may be wound wrong. The motor would pull less current running on the star winding and if it happened to have enough power to do the job this might get you by??
If the motor has enough power to do the job running it in star well not hurt it. If the motor is pulling less than 69 amps just raise your threshold setting. You could also take the leads feeding the other motor run them to the motor pulling to much and see if this makes any difference. This would let you know.
Good Luck

As is well known I am a little slow at times. I am not visualizing the system. Why are there 2 feed breakers? Depending on variables a 43KW motor (assuming 480vac) would be 69 amps...2 breakers set at 40 amps would be equal to 80 amps but not sure why it was done this way.

The lead swapping thing I mentioned above has to do with phase balancing, if there is a slight unbalance on the phases it can create current issues due to voltage drops etc that are not readily apparent but doubling the current does seem extreme.

Since this is a replacement motor have you checked all the mechanical aspects...bearings etc? Have you disconnected the saw(load) from the motor to see how it operates then...if it seems normal without a driven load then I would suspect a mechanical problem.

If you have a megger and the manufacturers specs then a test may be in order, a bad winding or improperly wound could cause this issue.

Well finally got hold of the OEM. Apparently they changed the style of motor to a constant torque (some magic internal to the motor) so that it pulls higher amperage all the time (even unloaded). When load is applied (cutting wood) the amperage only jumps slightly. Would have been helpful if they had sent a note to this effect so that I would have known in the middle of the night when no one is available to ask.

So appears this was all much to do about nothing. Thanks for all the input and quick responses. This motor cost $6000 so I was very cautious not to screw it up.

Thanks again

"Apparently they changed the style of motor to a constant torque (some magic internal to the motor) so that it pulls higher amperage all the time (even unloaded)."
Pls explaine in more details, because it sounds a liitle bit weird to me.

I wish I had more description to give you. All I can tell you is the peak amps under load of the two motors (old vs new) is about the same. When unloaded the new motor pulls near the peak amps and the old motor dropped to about half the peak amps. They (the OEM) says this is the way the new style of motors for there machines have been spec'd to provide a constant torque.


To me it seems to be a way to burn energy while it is not loaded.

NEMA motors

Hi,

In Europe NEMA motors aren't frequent, but there is diferent classes of motors acording to their torque and Amperage characteristic:
-NEMA class A: High start torque, low slipping (1%) and high starting current.
-NEMA class B: Standard motors (slipping 3%).
-NEMA class C: Standard motors with high torque (slipping 5%).
-NEMA class D: High torque, high slipping (8-13%) and low starting current.
-NEMA class F: Low torque, low starting current and standard slipping.

Excuse me by my english,

Kelkoon

rsdoran said:

This may sound stupid but give it a try, move all 3 phases...ie phases are A B C make it C A B.

We had a discussion on this at the other site but I can not find it now.

Click to expand...

That would be this thread, Ron....

Click here

I remember that topic as well, because that was the first time I had heard of rotating the phase connections to 'cure' an imbalance.

Paul