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Any motor experts on the forum?

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Ed Duffner04/03/2020 22:02:03
800 forum posts
91 photos

Hello guys,


At work I am trying to restore a Scabbler (concrete de-chipper) machine. Problem is, the motor makes a weird noise when running.

The motor is an induction type with permanent magnet rotor and a wound field-coil. There is no centrifugal switch and starting is handled by two 80uf capacitors wired in parallel.

It's switched on via a cylinder type, multi-pole switch which energises a contactor coil in a start position then springs back to a run position.

In the start position the motor sounds very smooth but when in the run position it sounds rough and the motor speed drops somewhat. It's like there's a choking effect or field being introduced.

I'm pretty sure I have wired the motor and controls according to the circuit diagram. Please excuse the use of an earth wire in one of the below photos, it's just a link, not an earth connection.

In the video I start the motor and release it twice so I can let you hear the 'choking' sound. It doesn't quite work on the first start.

 

I'd appreciate any ideas and your input as always.

Thank you,
Ed.

 

 

 

 

 
Contactor.

m1.jpg

 

Motor connections.

m3.jpg


On-Off-Start Switch.

m5.jpg


Circuit Diagram

m6.jpg

Edited By Ed Duffner on 04/03/2020 22:18:57

Edited By Ed Duffner on 04/03/2020 22:27:33

Simon Williams 304/03/2020 22:58:41
508 forum posts
80 photos

I think the clue is in the fact that it started OK the first time, and only made the straining noise when you moved the switch. That's a faulty switch. No I would definitely not be happy to let that go out of my shop behaving like that, but I think the fault is in the rotary switch.

Looks like it's a pretty standard sort of switch - the internals and the spring return will be specially designed for this application but you should be able to obtain a direct replacement.

If you would like to put up a photo of the labels on the switch which hopefully will show a manufacturer (Kraus and Naimer?) and a type number we can probably locate a supplier.

You may even be able to get a replacement from Marcrist as it seems to be their name on the drawing.

Worth spending the money for the right thing - should be £20 - 30 or thereabouts. While you're at it replace the contactor as well at the same time and have done with it. That looks to me like a Siemens contactor (edit - sorry the clue's on the picture it's Eaton if you blow it up big enough - but any similar contactor will do) - should be possible again to buy a direct replacement for about the same again. If you can get a picture of the label on the side of the contactor it will show manufacturer and part number.

HTH Simon

Edited By Simon Williams 3 on 04/03/2020 23:03:26

Ed Duffner05/03/2020 00:07:17
800 forum posts
91 photos

Hi Simon,

Thank you very much indeed for your expertise. It's always good to get another pair of eyes on a problem.

I can contact Marcrist to see about a replacement switch. The contactor was actually a replacement itself, some years ago but the machine was left in disrepair because it would not start at all. I traced that problem to an open-circuit thermal overload in the motor. I've bypassed that for now just to get the motor running. It'll be another required part, if its available.

Thanks again,
Ed.

Brian Morehen08/03/2020 08:28:07
avatar
81 forum posts
6 photos

Is this a single phase motor or a 3 Phase one that has been altered..

Brian

J Hancock08/03/2020 11:00:16
406 forum posts

Good point, details on nameplate worth showing here.

duncan webster08/03/2020 11:18:17
avatar
2591 forum posts
34 photos

I'm confused by the description as an induction motor with a permanent magnet rotor. Can anyone clarify?

Les Jones 108/03/2020 11:58:02
2130 forum posts
146 photos

I too have never heard of " an induction motor with a permanent magnet rotor ". I think Brian's question about it being a 3 phase motor that has been modified needs to be answered.

Les.

Brian Morehen08/03/2020 13:33:30
avatar
81 forum posts
6 photos

The motor name plate and details will teel us all a lot , This looks like a 5hp or more size motor. Are you running this through a 3ph Inverter .The motor sound chages when running I wonder if this is running on 2 phases because the inverter has brocken down and lost a phase .

Brian M

Steviegtr08/03/2020 15:18:32
avatar
1233 forum posts
115 photos

Look at the wiring diagram, lower right portion. It shows a single phase supply.

Steve.

Paul Barter08/03/2020 16:25:00
103 forum posts
7 photos

Sounds like a dud bearing, damaged ball or balls skidding rather than rotating.This may only be happening when the motor has run at full speed for a few seconds and a lack of lubrication and or roundness starts the music.

Paul

Mike Poole08/03/2020 19:30:43
avatar
2575 forum posts
60 photos

It is a single phase 110v machine, looks to be identical to a Von Arx machine.

Mike

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