Wiring up a single phase AC motor with 4 wires

[ell81Participant @ell81]

Well, 4 wires + 2 red ones. This motor is for a milling machine.

I want to just test the motor spins as it should before attempting to wire up the rest of it.

Could someone please tell me how to wire up this motor.

It does have a capactor with 2 wires coming from it, not shown in the pics.

That’s been taken off.

I still have it though.

As you can see with the 4 black wires, there’s 2 thin ones and 2 thicker ones.

 

The terminal is marked A1,A2,Z1,Z2

[noel shelleyParticipant @noelshelley55608]

A copy of tubal Cains model engineers handbook has several wiring diagrams, your motor has a start winding, a run winding, a capacitor and a centrifugal switch. It should be cap start – induction run.

WHY has it been completely dismantled ? I would check both continuity and earth leakage before doing anything else. The centrifugal switch is quite fragile and needs careful assembly and setting. Good luck. Noel.

[J HancockParticipant @jhancock95746]

The two thick wires  will be  the main winding.

The two thin wires are the  start  winding  connected  in series  with the capacitor.

[MacolmParticipant @macolm]

Always best to check wires and resistances carefully with a meter. In the diagram, A is the common connection scheme, but I have a motor with the start winding arranged like B. Still four wires!

[noel shelleyParticipant @noelshelley55608]

Neither A or B show a centrifugal switch so both in this context are wrong ! There are several circuits that could be right bearing in mind the limited info. At a rating of 1Hp it may have a cap missing and the centrifugal switch will act as a chenge over, there is also the possibility of a thermal overload. First step is to check the windings ! I can see no sign of colours, one convention was RED and BLACK = run,  Yellow and Blue = start. Noel.

[SillyOldDufferModerator @sillyoldduffer]

I agree with Macom that circuit ‘A’ is most likely.   This is my version with more detail and laid out to identify the position of the centrifugal switch. likely wire colours, and terminals.   WARNING – GUESS WORK!!!

Like Howard I’m worried about why the motor is in bits.  Often a very bad sign!  Might have been dismantled by someone casually interested in what’s inside, and will be OK provided it’s put back together again properly.   But more likely the motor broke down and someone opened it up and failed to fix it.

A common fault is that the enamel insulation has failed somewhere in the copper windings, and they are shorting out together and/or to the motor case.   Old enamel insulation might have aged badly, or – more likely – the motor got too hot due to being worked excessively hard for too long.  Howard recommended a continuity check, which can be done with an ordinary multimeter, and leakage test, which needs a Megger or similar.

The capacitors are very likely to fail, and are easily replaced.  But no-one should strip motor down to replace a  capacitor. Centrifugal switches get stuck or wear out their contacts.

The amount of dismantling shown in the pictures is excessive, suggesting the motor may have been done over in the past by an enthusiastic bodger.  That may mean a long list of extra faults.

Though possible to rewire a cooked motor, it’s cheaper to buy new.  Is it worth fixing this one?  It’s ancient, small(1 HP), in terrible condition, and potentially unsafe…

Bear in mind that a motor with faulty insulation is a potential widow-maker, so approach with caution.   Fires are more likely than electrocution, but fires cause far more casualties and damage than a 240v shock.  Safe enough if you assume the worst, understand the risks and take care, otherwise…

By all means have a go, but take care.   Repairing misunderstood motors without test equipment and based on internet advice  is well dodgy!  I might have got the circuit wrong.

Dave

 

 

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