3 Phase Motor Wiring Trouble 3

[phoenixMetal]

I am having trouble wiring a 3 phase motor to work properly.

The motor is 3 phase, switchable between 760/440/380/220 volts. It has a terminal block with jumpers to choose the input voltage. I have 208V 3 phase power.

When I jumpered it to 220V, the motor appeared to be running extremely fast and got hot. The motor is connected to a hydraulic pump, and from the sound the pump was making, it appeared that the motor was running faster than normal.

The motor works normally when jumpered to 440V, however it does not have enough power when a significant load is put on the system.

Here is the wiring diagram that came with the machine:

I noticed that for the 440V option, it shows a single Delta, whereas for the 220V option it shows TWO Deltas. Is this significant?

The previous owner of the machine had 440V power. Could there be anything in the machine's control box with any settings that need to be changed to allow for the changover to 220V?

Has anybody here ran into this problem or know a solution?

I appreciate your help!
Thank you,
Andrew (phoenixMetal)

 

[roydm]

For 440V you have 2 coils in series 220 V each.
For 220 V you wire the coils in parallel for 220V each.
My guess is somehow the coils got connected to the wrong terminals so when you connect them in parallel the two coils on each pair of phases are not together somehow changing the number of poles per phase. Either that or one winding is shorted out by the jumper.
I would take all the jumpers off and verify that each coil is connected to the apropriate terminal

A B C
1 * * *
A1-A3, B1-B3, C1-C3
2 * * *

3 * * *
A2-A4, B2-B4, C2-C4
4 * * *

I think that's how it goes.
It's possible that a coil cold be conected from row1 to row 2 instead of row 3 and it would still run ok with the 440V connections.
I'm sure there must be a simple trick for verifying the different coils are on the same pole.
Regards
Roy

 

[Skogsgurra]

This appears to be an Italian motor, probably designed for 50 Hz.

Then, it needs 264 volts if run at 60 Hz. You only have 208. So, you are 11-12% on the low side.

That increases slip around twice as much, which increases losses tremendously. No wonder the motor runs hot. It shall.

Struggling to run at 20 percent overspeed, it is possible that it makes the pump run faster than expected, hence the sound.

Conclusion (if you are running this off a 60 Hz grid, which the 208 V indicate): The connection is OK. But the voltage and the frequency is wrong. Not much to do about that except changing motor or use a step-up transformer to get 264 V. The motor will then run at twenty percent overspeed and that may also present a problem - or not.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

The reason that the motor seems to be running faster on 208 V is that it would be running too slow on the 440 V connection.
If you can find 3 transformers rated 120:32 V you can use then as a wye connected autotransformer bank to boost the voltage.
The 32 V winding must be capable of carrying the motor full load current.
If you an find transformers rated 208:56 V, or 240:60 V
or 480:120 V you can use an open delta autotransformer boost.
Again the secondary winding must be capable of carrying motor full load current. 208:48 V would be close enough.
As Gunnar pointed out, the pump will be running faster and may overload the motor in any event.
How about a VFD and let the VFD sort out the details. 47 Hz or so would be right for 208 volts. Close enough that you could push it up to 50 Hz.

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

 

[phoenixMetal]

Hey Guys, thanks for your posts - you know a lot!

As Skogsgurra pointed out, this is an italian motor, however it is rated on its nameplate for 50/60hz, so it should be able to handle the 20% overspeed. But your note about the need for an actual 264V (220V + 20%) is interesting - I never thought about it that way.

As Waross pointed out, perhaps my perception of the motor running too fast when wired at 220V is due to my baseline expectation being based on it running too slow when wired at 440V. However, having been around a handful of machines with hydraulic systems, the pumps all tend to have a similar sound. While wired at 440V, its sound was within that normal range, but at 220V it was significantly abnormal sounding (much higher pitched whine), telling me that it running quite a bit faster than +20%.

I will first double check that a winding isn't incorrectly shorted out by a jumper as suggested by Roydm earlier.

Thanks for all your help and keep it up!

-Andrew (phoenixMetal)

 

[waross]

It is not impossible for an induction motor to run above base synchronous speed but it can happen. Depending on how your winding coils are placed physically in the stator, you may have created a consequent pole motor which will run at twice base speed and get very hot very soon.
This could happen if all the connections to one of the two deltas were inadvertently reversed. It takes a combination of the "right" wrong connections and the right physical placement of the windings in the stator. Not likey but possible. And, if through a misunderstanding, one winding is connected backwards, the same mistake could easily be made on the other two.


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

 

[edison123]

but at 220V it was significantly abnormal sounding (much higher pitched whine), telling me that it running quite a bit faster than +20%.

.

That was not a speed whine. It was due to wrong connection at 220 V. Did you measure all the three line currents ? If they are significantly different from each other, then the winding is wrongly connected either at the terminals or internally.

 

[waross]

I apologize for my mis-information. An inadvertent consequent pole connection will make the motor run slower, not faster. I am sorry for any confusion I may have caused.

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

 

[LionelHutz]

I'd check what Roy suggested. The motor could also have a coil reversed. I think you'd need a motor shop to help determine that.

Did you measure the current going to the motor?

Was this overheating with the pump loaded? I'm thinking not considering your testing on 440V but thought I'd ask anyways.

If this is a 50hz system being run on 60hz then the pump is running over speed and that will cause it to load the motor much more than when running at 50hz.

 

[zlatkodo]

You must change winding data and calculate new windings for your voltage and freq. only.
See:

http://www.youtube.com/watch?v=guPfSCPNiZI

Zlatkodo

 

[burnt2x]

"My guess is somehow the coils got connected to the wrong terminals so when you connect them in parallel the two coils on each pair of phases are not together somehow changing the number of poles per phase. Either that or one winding is shorted out by the jumper.
I would take all the jumpers off and verify that each coil is connected to the appropriate terminal

Another presentation how to do what roy meant, as I understand it, please see attached.