Change of direction a single phase capacitor run motor

Gentlemen,

Can anybody advise on the change of direction of a single phase capacitor run motor please.

Thanks,

Martin P

swap the two ends over on the main winding...

Edited By John Rudd on 14/12/2018 10:59:22

Or indeed the other winding, or use this approach...

The above is the recommended Parvalux circuit to reverse I think the SD13 motor as used on the Quorn. W1 and W2 need to be identical for it to work properly. Somewhere on this forum I gave some analysis and measurements on the SD13 to show how it works.

Sometimes you can do a mechanical swap by taking the rotor out of the stator, and replacing it back to front, then fitting the two end bells opposite way round. I did this for a motor where the wiring wasn't accessible though it does rely on the rotor having the same size and type of bearings both ends.

Season's Greetings

Simon

A number of solutions, depending on what you want as a final outcome.

If merely to reverse the direction of rotation of the driven item.

1) Turn the motor end for end, assuming that there is enough space.

2) As already suggested,dismantle and reassemble with the rotor installed the other way round

3) Modify the connections, to the windings, as shown.

If wanted as being capable of running in either direction, at will, (possibly to drive a lathe mill) then the ability to change the connections to windings needs to be by some form of changeover switch, such as the old fashioned Dewhurst Drum Switch .

In this day and age, H & S would want some form of No Volt Release switch in the circuit, for safety in the event of a temporary mains failure.

Howard

Edited By Howard Lewis on 14/12/2018 14:59:55

Stricly that amounts to mounting the stator back to front, leaving the rotor the same. Since the rotor has rotational symmetry, rotating it end for end has no effect. Swapping the stator would only work in an existing machine if the stator is symmetrical about the axis perpendicular to rotation, otherwise the ends of the shaft will be in the wrong axial position.

Do as John Rudd has said,however it's not always obvious which is the run winding. To locate the run winding carefully mark all wires before disturbing any of them, possibly take a photo with your phone.If you have an ohmmeter disconnect one of the A wires ( assuming the motor is an old one made in UK) and locate the other end, then reverse the pair. The run winding will have the lowest resistance and thicker wire. John

Hi Martin,,

At the risk of Hijacking your thread,could I ask a question of the other Members?

I have a small 1/4HP motor,made by Hoover,single phase,no cap,very smooth running and quiet.

So far,so good ! Problem is that it cannot make up its mind which way it wants to run,no kidding !

Switch on to-day,it goes one way,tomorrow ? who knows,could be either way.

This is less than helpful,to put it mildly.

Anyone got any ideas how to help it on its way [one way or the other ]

IT,S 1425 REVS so a useful item .I had in mind to use it for a disc sander,but as it is,it would make life interesting !

Martin

Do as John Haine suggests, the switch used is a single pole double throw (SPDT), best to get one with a centre OFF position.

The power in goes to the centre switch terminal and wires from the outer 2 terminals connect to the capacitor leads/windings ends.

All the switch does is put the live power to 1 or other side of the capacitor, this is as John says the recommended method of switching/reversing Parvalux capacitor start and run fractional horse power motors.

To change direction of a single phase induction motor with start and run windings reverse the ends of the start winding, this will normally be connected through a centrifugal switch.

Emgee

The theory is good as long as the two windings have the same characteristics, i.e the same impedance/wire gauge/ number of turns...

Hello Larry I've sent you a Pm regarding your motor. John

Thanks John,

Just got that message now. Will check that out tomorrow,as you say,they are a nice little motor.

Again,many thanks.

to reverse a single phase motor, be it capacitor start, or capacitor run, or both, with or without centrifugal switch, you reverse the polarity (swap over the connections) on the START winding, changing the polarity of the run winding will have no effect, as a single phase motor will always run in the direction it is started in. The start winding , measured with a multimeter, will have a higher resistance than the run winding.

John, that's why I also stated the Parvalux example used in John's sketch.

Emgee

Emgee, my apologies, I dont s'pose many folk would realise that Parvalux motors can be treat that way, nor would they necessarily know the attributes of start run windings...

Got an old AEI thread here

I presume if you run the two wires out to a dewhurst type switch and back in to C and D you can have both directions on tap

Edited By Ady1 on 15/12/2018 08:03:13

Hi John, you were correct to point to checking windings resistances to establish type of motor, the method suggested for Parvalux will clearly not suit differently wound motors.

Thank you all,

When the temperature goes slightly positive, maybe tomorrow, I will go and have a play.

Martin P

This only works with symmetrical windings, otherwise the smaller winding ends up doing the work.