Help with lathe motor capacitor

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Help with lathe motor capacitor

This topic has 24 replies, 7 voices, and was last updated 28 March 2021 at 12:36 by Mark H.

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21 March 2021 at 14:08 #10758
Mark H
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@markh20821
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21 March 2021 at 14:08 #535221
Mark H
Participant
@markh20821
Guys, I'm on with restoring a old pools 4" special lathe, the motor on it is a brooks crompton (I could just about see the sticker) but I don't know any of the spec as the sticker was very faded… Has MH097849 stamped on it

I need a start capacitor but no idea of uf rating…any idea's?

The motor is a single phase 240v

When the power is switched on, the motor hums but I needed to spin the pulley on the lathe to get it running. There is only provision for 1 capicator (ive got the cap cover and there is 2 spade end wires coming out from the motor) so i assume its a combined start/run capacitor I need?

Thanks
21 March 2021 at 14:32 #535227
Dave Halford
Participant
@davehalford22513
Is the cap body not marked?
21 March 2021 at 14:42 #535230
Harry Wilkes
Participant
@harrywilkes58467
Mark see is there's any info here link http://www.lathes.co.uk/pools/

H
21 March 2021 at 15:14 #535246
John Haine
Participant
@johnhaine32865
You probably wouldn't go far wrong with an 8uF start capacitor from RS or Farnell
21 March 2021 at 15:27 #535248
Phil Whitley
Participant
@philwhitley94135
and make sure it is 400v working capacity! I agree with John 8uF will do it!

Phil
21 March 2021 at 20:03 #535327
Mark H
Participant
@markh20821
Posted by Dave Halford on 21/03/2021 14:32:50:

Is the cap body not marked?

No cap fitted when I got it, spin to start !!
21 March 2021 at 20:05 #535328
Mark H
Participant
@markh20821
Thanks guys, I'll try a 8uf
21 March 2021 at 21:03 #535332
JohnF
Participant
@johnf59703
Give the chaps at Power Capacitors / Trnaswave in Birmingham a call I'm sure they will advise, I had a problem with a compressor motor the makers agent wanted an eye watering sum for a replacement I think PCap charged about a fiver !

John
21 March 2021 at 21:51 #535341
noel shelley
Participant
@noelshelley55608
Is there a circuit diagram on the terminal cover. ? As has been said it MUST be 400V. There are several ways to start an induction motor, from split phase to numerous ways to use a centrifugal switch. The important thing is that the motor spins up almost instantly, if it stays on the start windings for more than a few seconds it will soon cook ! Noel.
22 March 2021 at 07:59 #535373
Mark H
Participant
@markh20821
The motor fitted looks very much like this:

Motor

The wiring is 4 wires coming from the top, only 2 were connected to the main plug so that must be the run circuit, the other 2 wires, i assume would be direction..

Once i source a cap, im i right in thinking, i will need to wire in the spare 2 wires for the direction?

There is 2 wires for the missing capacitor, ive got the cap cover.

When plugged in the motor hummed but you had to spin the pulley (in either direction) to get the lathe to turn, the guy has been using it for years like that but i dont fancy it !!

Would this be ok for a cap: Cap

Thanks

Edited By Mark H on 22/03/2021 08:02:50
22 March 2021 at 08:28 #535379
John Haine
Participant
@johnhaine32865
Made for the job.
22 March 2021 at 09:29 #535388
noel shelley
Participant
@noelshelley55608
Now we have more of the story/history it could be that the start windings are cooked rather than just that the capacitor is missing. I would check the resistance of the windings. What letters are on the terminal plate ? If when you wire it up it spins in the wrong direction the start winding connections will need swaping over, BUT only the start. Good Luck Noel
22 March 2021 at 13:51 #535422
Mark H
Participant
@markh20821
Posted by noel shelley on 22/03/2021 09:29:19:

Now we have more of the story/history it could be that the start windings are cooked rather than just that the capacitor is missing. I would check the resistance of the windings. What letters are on the terminal plate ? If when you wire it up it spins in the wrong direction the start winding connections will need swaping over, BUT only the start. Good Luck Noel

No markings on the terminal plate, the 4 wires just come out of the motor body into the plastic housing, i'll get a pic up as it will make more sense…
22 March 2021 at 19:29 #535451
Mark H
Participant
@markh20821
Hopefully a pic of the motor…

Edited By Mark H on 22/03/2021 19:43:06
22 March 2021 at 19:47 #535459
Mark H
Participant
@markh20821
The red and black wires were connected to the mains plug, the blue/brown wasn't connected at all

Edited By Mark H on 22/03/2021 19:49:05
22 March 2021 at 21:47 #535466
noel shelley
Participant
@noelshelley55608
black and red are the correct colours for the run windings ! Blue and yellow were the normal colours for the start. In your case blue and brown. One has to assume that there is internal wiring for the centrifugal switch ! Therefore capacitor to the two spade connectors on the side – do you have the proper cover for the capacitor as the terminals will be at mains potential 240Volt. Live and neutral to red / black and blue / brown. If the direction of rotation is wrong then swap blue and brown. Good luck, Noel
23 March 2021 at 22:25 #535685
Mark H
Participant
@markh20821
Yep, i'll got the cover for the Cap
27 March 2021 at 15:25 #536532
Mark H
Participant
@markh20821
Well, this is confusing me, red/black connected, motor runs but anti clock, needs to be clockwise.

Brown/blue, I can connect to br/red and blue/black and runs anti, if I swop them, the rd trips..

If I just use red/black but swop them, motor runs anti, I can connect blue/Brown to mains and still runs anti.

Without cap I can get it to run clock if I spin the pulley, with cap connected..anti

No wire combo with cap fitted seems to get the motor to run clock only anti..

Wonder if something is knackered in the motor ??
27 March 2021 at 15:26 #536533
Mark H
Participant
@markh20821
I'm wondering because its a old motor, it only runs in one direction, thats why the cap had been removed so you could manually spin the motor clockwise to start it…..

Edited By Mark H on 27/03/2021 15:45:22
27 March 2021 at 15:26 #536534
Mark H
Participant
@markh20821
Edited By Mark H on 27/03/2021 15:48:35
27 March 2021 at 19:35 #536582
Dave Halford
Participant
@davehalford22513
I suspect it may be only running on the start coil only with one of your swaps.

Search on cap start and induction run motors, you will get wiring diagrams

It should reverse if you swap the connections of the capacitor where it meets the run coil and the start coil where it meets the run coil.

Measure the resistance across both motor bn to bl and also r to bk, the lowest resistance is the start coil if you disconnect the cap that one should go high resistance.

You will need to take the back plate off the motor, where you should find the centrifugal switch. Leave the switch wiring alone but look at the cap wire colours and see what it changes to, one leg will go to the switch on the end plate ignore that one.

Edited By Dave Halford on 27/03/2021 19:39:38
27 March 2021 at 21:27 #536600
Mark H
Participant
@markh20821
Posted by Dave Halford on 27/03/2021 19:35:59:

I suspect it may be only running on the start coil only with one of your swaps.

Search on cap start and induction run motors, you will get wiring diagrams

It should reverse if you swap the connections of the capacitor where it meets the run coil and the start coil where it meets the run coil.

Measure the resistance across both motor bn to bl and also r to bk, the lowest resistance is the start coil if you disconnect the cap that one should go high resistance.

You will need to take the back plate off the motor, where you should find the centrifugal switch. Leave the switch wiring alone but look at the cap wire colours and see what it changes to, one leg will go to the switch on the end plate ignore that one.

Edited By Dave Halford on 27/03/2021 19:39:38

Thanks Dave, I'll see how I get on, be a shame to buy another motor if I can suss this one out…..
28 March 2021 at 00:11 #536617
noel shelley
Participant
@noelshelley55608
As so often happens, the fault may be a simple one, IF you have the test gear and know how to use it. The best plan may now be to strip the non drive end off and check the internal wiring and the centrifugal switch. If the C switch is sound, the insulation is good, and the windings have not been cooked then there is every chance that the motor can be got working.The first thing is to assertain which starting circuit is being used, as there are several.

Having twice in the last 3 months seen a type of motor wiring diagram that I did not know existed at first, to be told I was wrong when the poster had shown said diagram and it's operation was obvious because I had seen a motor of this type apart still counted for nothing in some's eyes. The fact that the diagram was also published in the Model Engineers Handbook by Tubal Cain still counted for nothing. It has been said by some that giving advice to an unskilled man on the subject of 240V electrics is to put said mans life at risk in this brave new world we live in. All I can do is offer advice and hope that common sence will prevail, or if you are not to far off and can travel I will test and if possible fix it. Good luck Noel
28 March 2021 at 12:36 #536693
Mark H
Participant
@markh20821
Posted by noel shelley on 28/03/2021 00:11:10:

As so often happens, the fault may be a simple one, IF you have the test gear and know how to use it. The best plan may now be to strip the non drive end off and check the internal wiring and the centrifugal switch. If the C switch is sound, the insulation is good, and the windings have not been cooked then there is every chance that the motor can be got working.The first thing is to assertain which starting circuit is being used, as there are several.

Having twice in the last 3 months seen a type of motor wiring diagram that I did not know existed at first, to be told I was wrong when the poster had shown said diagram and it's operation was obvious because I had seen a motor of this type apart still counted for nothing in some's eyes. The fact that the diagram was also published in the Model Engineers Handbook by Tubal Cain still counted for nothing. It has been said by some that giving advice to an unskilled man on the subject of 240V electrics is to put said mans life at risk in this brave new world we live in. All I can do is offer advice and hope that common sence will prevail, or if you are not to far off and can travel I will test and if possible fix it. Good luck Noel

Thanks Noel, I'll get my meter on it to suss out the circuit, ive wired the motor to a NVR switch.

I'm in morecambe in the NW
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