Half speed motor issue

Mr.Green · May 28, 2019

Have a 3hp direct drive motor that is running about half speed 1750 vs. 3500 judge by ear and the high amp draw, 25 amps continuous.

9 lead motor, I added onto the leads, left original numbers intact, paired leads (Y connected motor, 3, 2, 2, 2)

Rang it out, leads matched up.

Rotated 7,8,9 rang out again, which changes other pairs, still half speed.

Rotated again, same results.

Trying to avoid motor shop since I have to take entire machine, not pulling stator again unless at gun point.

What could be going on?

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9100 · May 29, 2019

Only a guess, you may have a winding reversed, effectively cancelling that pole. Three of the windings will have their commons connected so you will read continuity between them, the other windings have their commons separate. disconnect those and leave them open, then connect 240 three phase to the three remaining windings. The motor should run at normal speed but you will only be able to load it to 1/2 horsepower. If that works, you then need to identify the polarities of the remaining windings.

Bill

SAF · May 29, 2019

You likely have your windings crossed. On your typical 9 lead dual voltage motor, #7,8,9 should never be rolled.

It would be helpful if you stated the voltage your trying to run at, along with the motor tag data.

Here is a winding and connection diagram for both voltages. I suggest that you separate the leads, and check your wire tags against the winding diagram.

SAF Ω

Mr.Green · May 29, 2019

SAF said:
You likely have your windings crossed. On your typical 9 lead dual voltage motor, #7,8,9 should never be rolled.

It would be helpful if you stated the voltage your trying to run at, along with the motor tag data.

Here is a winding and connection diagram for both voltages. I suggest that you separate the leads, and check your wire tags against the winding diagram.
View attachment 257676

SAF Ω

7,8,9 pair, 3,6 pair, 5,2 and 4,1 all pair.

You use 7,8,9 to identify which of the other 3 sets each one is, then you can figure out which lead is which by watching your deflect on the meter when you flash 7,8, or 9 depending on what leads you are trying to determine.

Motor originally shipped 440v, at some point it was either rewound (doubtful as the winding insulation looks very 1940s typical) or the stator was wound for both voltages, but the connections were made internally and only 3 leads were brought out for 440v.

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CarlBoyd · May 31, 2019

According to the diagram, for low voltage operation you should connct:
T4,T5,T6 together.
T1 and T7 to power 1
T2 and T8 to power 2
T3 and T9 to power 3

Mr.Green · May 31, 2019

CarlBoyd said:
According to the diagram, for low voltage operation you should connct:
T4,T5,T6 together.
T1 and T7 to power 1
T2 and T8 to power 2
T3 and T9 to power 3

Apparently many don't know anything about ringing out a motor.

I am fully aware how to wire Y, or delta wound motors for high or low voltage, even Y start delta runs.

To me, there is an issue with a winding, unfortunately I don't own a megger yet, and I have tried every combination of 7,8,9 while ringing out the motor in order to make sure all leads were correctly identified.

I am currently over it, moved on to other projects and it will get hauled to the motor shop next week.

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atomarc · May 31, 2019

Sheesh..you came here with a problem and now your busting peoples balls who are trying to help. You need to get over more than your funked up motor Mr.Green Jeans.

Stuart

Mr.Green · May 31, 2019

atomarc said:
Sheesh..you came here with a problem and now your busting peoples balls who are trying to help. You need to get over more than your funked up motor Mr.Green Jeans.

Stuart

No, so far there was one person who actually read my first post. I never asked how to wire a Y wound motor for low voltage.

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atomarc · May 31, 2019

It would seem to me, from a purely deductive standpoint, if the motor worked as it should from the factory, you added some new motor lead extensions and now it doesn't work, that you did something wrong. Maybe that number '6' is really a number '9'..!

Stuart

Mr.Green · May 31, 2019

atomarc said:
It would seem to me, from a purely deductive standpoint, if the motor worked as it should from the factory, you added some new motor lead extensions and now it doesn't work, that you did something wrong. Maybe that number '6' is really a number '9'..!

Stuart

No, it ean like that the first time I put a wire to it, didn't change a thing. Pulled stator, inspected leads, put back together, decided that 12" of extensions on the leads would make it easier to work on.

I have paired and numbered leads in many motors that came to me unmarked.

It's about a 33% chance of getting it correct the first time ( you know what 3 leads are 7,8,9 but not necessarily which one is which)

It's a process, but not a horribly difficult one.

This one just has me stumped.

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SAF · Jun 1, 2019

Identifing Unmarked Motor Leads

Mr.Green said:
Trying to avoid motor shop since I have to take entire machine, not pulling stator again unless at gun point.

What could be going on?

Sounds like you need to invest in a megger, and take your gun in with the machine, if that's what you need to get the stator out with. Ask the motor shop to run the rotor on the growler first, before putting the gun to your head, to pull the stator out..

My local motor shop wont touch any machine, with the motor installed and wired, motor needs to be free for bench testing.

For the others interested, here is a paper with instructions to flash the windings for identification. 6 & 9 lead units. By: Augie Hand

https://www.repairzone.com/documents/tech_notes/9_lead_connection_sheet.pdf

And a video explaining the process.

Repair Zone Videos - Identifying Unmarked 9 Lead Motors WYE Connection

Repair Zone Videos - Identifying Unmarked 9 Lead Motors: Delta Connection

SAF Ω

Mr.Green · Jun 1, 2019

It's a direct drive machine, fishing the wires back in through the tiny hole in the motor housing sucks. I have had to take a couple other complete machines to them.

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9100 · Jun 1, 2019

Mr.Green said:
No, so far there was one person who actually read my first post. I never asked how to wire a Y wound motor for low voltage.

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Did you read my post? First, you have refused to tell us what voltage you want to run on. I told you how to quickly test the motor by connecting 240 three phase to the wye windings. It would only be good for 1/2 of its horsepower but if it was good, it would run.

I'm not sure why I even bothered to respond.

Bill

Mr.Green · Jun 1, 2019

9100 said:
Did you read my post? First, you have refused to tell us what voltage you want to run on. I told you how to quickly test the motor by connecting 240 three phase to the wye windings. It would only be good for 1/2 of its horsepower but if it was good, it would run.

I'm not sure why I even bothered to respond.

Bill

Yes, it was set up at 240v. I actually screen shot your post. I haven't touched the machine since Monday. Had a bunch of other stuff come in I had to deal with, like redoing the control circuits on a resaw, breaking down a few motors for bearings, kids, etc.

I believe I tried what you suggested as I tried switching 1,4, test, put back, switch 5,2, etc. I believe the results were a locked rotor everytime along with a couple blown fuses.

I didn't get to the rest of the combinations though.

Yes, I need a megger. It's the last thing I really need for motor work. It was hard to track down an analog meter that read in millivolts.

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9100 · Jun 1, 2019

I said to connect power to the three coils connected in Y, normally marked 7, 8, 9. Leave all the other leads open, not connected to anything. The motor should run normally with no or a light load.

Bill

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