electric motor rewinds

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electric motor rewinds

This topic has 11 replies, 6 voices, and was last updated 18 April 2013 at 15:45 by Les Jones 1.

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17 April 2013 at 10:08 #22584
Rufus Roughcut
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@rufusroughcut
rotation changes after rewinds
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17 April 2013 at 10:08 #117137
Rufus Roughcut
Participant
@rufusroughcut
I have recently had a 1800 watt three lead 240v brushed motor rewind and when refitted it ran in reverse, does any member know if this can be corrected by swapping the brush leads

Edited By Rufus Roughcut on 17/04/2013 10:09:44
17 April 2013 at 10:50 #117140
roy entwistle
Participant
@royentwistle24699
May I suggest you contact whoever did the rewind
17 April 2013 at 15:21 #117153
Les Jones 1
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@lesjones1
Hi Rufus,
Is the motor AC or DC ? If it is AC then it is probably series wound. (Also called universal as it could run on either AC or DC). If it is DC then is it series wound, shunt wound or permanent magnet ? When you say it is three lead do you mean two plus earth or or three wires plus earth ? If it is three wires plus earth then how is it connected ?

Les
17 April 2013 at 18:56 #117162
Rufus Roughcut
Participant
@rufusroughcut
Hi Les

Sorry yes 240V AC Induction with three wire being a start coil and run coil wound stata the three wires seem to be Black thin start coil IN, Brown thicker run coil IN and Blue thin and thick coils return ????? the other end Brush A has a thick wire (Brown) and Brush (B) has a thin and a thick wire (Yellow). I've since swapped the incoming Blue and Black wires and the rotation has changed to correct rotation however when stopped it stops dead and I felt this may not be correct way of swapping rotation, No sign of any earth wires at the motor which is fitted in a table saw.

Barry

My real queary was would altering the connections over on the brushes change the direction of rotation on this type of motor
17 April 2013 at 19:22 #117164
Sub Mandrel
Participant
@submandrel
Hi Barry,

The direction of rotation can be reversed by swapping the connectuions of one coil, as you have done. I have seen this described as normal practice several times.

Check this link

Neil

Edited By Stub Mandrel on 17/04/2013 19:25:59
17 April 2013 at 19:38 #117166
RJW
Participant
@rjw
Barry, are any of the wires for the brake clutch?

Table saws if of fairly recent manufacture have a brake on one end of the motor, and a characteristic is that the motor stops quickly when they're switched off, it's a safety feature, my table saws and bandsaw are fitted with them!

Can't quite remember just how they operate but I seem to remember a 'fly' type governer on the brake which activates the brake circuit when the motor is up to speed, but 'activation' keeps the brake 'off', when the stop button is hit, the circuit to the brake is cut and and the friction discs are released which brakes the motor – and the blade, Fast!

John
17 April 2013 at 19:58 #117173
Rufus Roughcut
Participant
@rufusroughcut
Hi Neil

Thanks for the link

Hi John

No fancy clutches here, it just seem to dump all the motive power through the brushes to never never land

Barry
17 April 2013 at 20:29 #117184
Les Jones 1
Participant
@lesjones1
Hi Barry,
I have not come across an induction motor with brushes. Without knowing how the brushes are connected to the start and run stator windings I have no suggestions. If the brushes are just connected together and not to the stator windings it could be a repulsion motor as described in Neil's link. Are there any other components such a capacitor in the box that the three wires connect to ? Do the three wires connect to three separate terminals or are there just two terminals with two of the motor wires connected to one of the terminals ?

Les.
17 April 2013 at 20:46 #117188
Rufus Roughcut
Participant
@rufusroughcut
Hi Les

Thanks, I think I'm gonna take the switch box appart to see what's hidding in there may be Capacitor/PCB secrets not yet discovered, also I'm inclined to fit the leads back in wrong rotation and swap the brush leads to see what happens and update

regards

Barry
18 April 2013 at 11:28 #117240
Ian S C
Participant
@iansc
I imagine that this is a repulsion start machine, where the brushes are lifted and the comutator shorted on reaching running speed, I don't think there are that many of this type around these days. Ian S C
18 April 2013 at 15:45 #117258
Les Jones 1
Participant
@lesjones1
Hi Barry,
I have had no experience of repulsion start motors so I did a web search. This revealed that there IS NO ELECTRICAL CONNECTION between the stator winding and the brushes You could verify this with a multimeter. As you say that there are two stator windings but only three wires then one of the wires must be connected to the junction of the two windings. I SUSPECT that one of the windings will need to be reversed which will require access to the inside of the motor where the end of the two windings are joined together. I think the recommendation in first reply you had from Roy Entwistle is the way to go.

Les.
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