Unknown motor 5

[Jwprice84]

I have an old motor that has been rewound incorrectly, I have no information on the motor does anyone recognise the type of motor it could be from the pictures, I have been told it may possibly be an old mod motor off of a ship

 

[dArsonval]

The lengthy end bracket register fit somewhat suggests the motor was possibly intended for use in a hazardous location.

"But", the hefty register fit combined with the robust opposite drive end shaft... could also imply a large item was mounted to the motor's output shaft. (A big fan blade perhaps.)

It'd be interesting to see a view of the stator winding.

John

 

[edison123]

Going by the long shaft and the middle of the frame mounting, I would say a stirrer (vertical mount) or a fan on a horizontal mount. Probably 4 poles (1500/1800 RPM) to 6 poles (1000/1200 RPM) at 50/60 Hz. Going by the long shoulder/rabbet and sturdy construction, probably Ex class motor. Guessing around 5 to 7.5 HP.

What is your speed requirement? A good rewinding shop can do a stator winding redesign from scratch.

Muthu

http://www.edison.co.in

 

[Jwprice84]

Thank you for the info, it is used as an extractor motor, not sure if the blade attached is original

It was rewound and bearings replaced by one firm and since then when the blade is attached it overheats, it was perfectly fine for 40 years but there only answer was the blade is probably too heavy. A second firm have tried fixing it but said after the repair that they only copy wind so if the windings are not right there is nothing they can do

 

[waross]

I am sorry for your lo$$.
By the time it is rewound again the cost may be three times the cost of a new motor.
The only time a motor that small is rewound is if it is a special, very expensive motor.
If the motor is to be returned to the original service, you may be stuck with the cost of another rewind.
As a WAG, (Wild Assed Guess) It may have been a 950 RPM motor and the shop stripped out the original winding without checking the number of poles. Then it was rewound for the more common speed of 1450 RPM,
You may talk to the original shop again and suggest that they rewind it for the original speed.
By the way, do you know the current that it draws, before and after the rewind, if possible.
Failing that, can you describe how fast the motor heats up?
You may consider a large disk mounted on the propeller blades to block some of the air flow.
If you go with this red-neck fix, you will probably be surprised at how large the disk must be to be effective.
Even better, if you can get it balanced, would be a ring, so that cooling air may still pass over the motor directly.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Jwprice84]

Here are some pictures of the stator windings from the taken front of the motor

 

[Jwprice84]

I dont know what current it draws, the motor is too hot to touch and has a burnt winding smell after 30 minutes of running

 

[edison123]

Thanks for pics. It is clearer now.

It's a 24 slots, 4 pole, 1500/1800 RPM, 50/60 Hz stator winding. Possible reasons for overheating a) new blade is heavier than the old one or b) winding design is wrong (too many turns resulting in less ampacity). The workmanship of winding is not great either but that's not the reason for overheating.

Muthu

http://www.edison.co.in

 

[Jwprice84]

The fan blade has been used on the motor since 1978 running 8 hours a day and I have had it balanced also so doubtful that's the issue. I was hoping the first firm may have used a sub standard grade of bearings but it seems like the most likely answer is the windings are incorrect. I have been trying to get it repaired as where it is installed it will be alot of work to change the mountings and I haven't seen any other motors that are mounted the same way

 

[edison123]

I was going by your 'only answer was the blade is probably too heavy' which gave the impression the blade was changed. If the blade was original, then the winding design is wrong and I suggest rewinding it with a better repair shop since I doubt you can source an identical motor with this type of construction.

Muthu

http://www.edison.co.in

 

[Jwprice84]

Does anyone have any decent recommendations for a repair shop? I obviously am not good at judging after 2 attempts. I need to find somewhere that won't just copy the windings again

 

[waross]

Consider a complete fan assembly.

Another option may be to mount the fan on a jack shaft.
Replace the motor with a plate with a pair of bearings to support the jack shaft.
Then belt drive it from the side with an off the shelf motor.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

By the way, try running the motor for a half hour without the fan.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Jwprice84]

It runs ok without the fan doesn't overheat, it's only with the blade attached that it struggles seems like it's trying to draw too much power and spinning too fast, attached is a sound clip of the noise it makes motor is running at the start, power is cut 8 seconds in and restarted 13 seconds in. Before the first repair it ran pretty much silently after reaching full speed

 

[dArsonval]

The audio "WAV" file adds an interesting troubleshooting tool to this thread.

Unrelated to the re-wind issue...
It kind of sounds like a bearing noise ramps down in amplitude after the motor is shut off indicating a mechanical issue
in addition to the incorrect stator winding. If it were an electrical noise, it would disappear immediately upon cutting power.
It also sounded to me as if the motor took longer than necessary to come up to speed for the size it is.
Almost as if it was trying to start on a lower voltage. Others may chime in on what they hear and offer their interpretation of the noise.

As for finding a repair shop, here's an option:

https://my.easa.com/find/active

Depending on where you are located, fill in what blanks you can, and scroll the results.

But here's the thing. Just because a business may be listed, it does not mean the repair shop is competent.

Not all shops have state-of-the-art resources and equipment.
And not all shops have people aboard who can competently develop a winding for a bare core.
So in seeking out help... it will be necessary to explain you're looking for a shop that can redesign, or reestablish a winding.

Don't rely on, "Oh sure, we can do that." Explore their oh sureness with additional questions.

Today, developing a winding for a bare core has been simplified by computer software.
Once upon a time, shops had to do all the math with a calculator, determine stator-rotor slot combinations, approximate flux densities,
and chord factors utilizing published charts etc. Computer software has streamlined the whole process now.

If you decide to get it fixed AGAIN... I wish you productive success.

John

 

[edison123]

With 24 slots, it is unlikely the original winding was 6 pole, 1000/1200 RPM. So, the fan is not spinning faster than the original 4 pole, 1500/1800 RPM from before. It's overheating due to excess turns and poor ampacity.

As John says, EASA is a very good source for locating good motor doctors in your area.

Muthu

http://www.edison.co.in

 

[waross]

Winding Gurus: Could it be as simple as a star connection that should have been a delta connection?

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[edison123]

Good point, Bill. That could explain the heating (too many turns for a star connection and more current density at full load).

Pity only 3 leads are brought instead of 6, which would allow changing the connection. Now, the delta connection has to be done at the winding.

Muthu

http://www.edison.co.in

 

[RedSnake]

If some one would have played that for me and just sade it is a motor and nothing else.

I would say the the first 8 sek sounds as a bearing fault.
The second sound: it sound as if it is a direct start but would have needed a Y/D start, or a Y/D start where the timing is off.

The first part of the second try it sound as dArsonval says, as if it is stuck or the power isn't enough.

We hade a problem with a hydraulik pump that didn't angel back when going on max pressure and when the power "ran out" and it started to slow down and stop it sounded like that. whaaooooOOOO...

Is the sound file with or without the blade?
How is the motor started?
And are the sound file taken when the motor is in ordinary place or is it been tested at work bench?

I was hoping the first firm may have used a sub standard grade of bearings but it seems like the most likely answer is...

And it is confirmed that it wasn't a substandard bearing?

Another observation is that the stator is very scratched.
I am no motor "specialist" so I will ask all the "stupid" questions.
How is the stator centered so that the rotor do not start, do not know the EN word for this rubb against it?

It seems like a heavy blade a little unbalance can make a lot of problem if the bearings can't stabilize the unbalance.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[waross]

I was unable to open the sound file, but from the descriptions of the sound, could that be consistent with a star connection that should have been delta?
A question to the shop on the possibility of a wye/delta mistake may be productive.
There is nothing wrong with the winding, just an easily made connection issue.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!