Motor problem

[p0689109]

Motor windings

How come it only shows two inputs if it is 3 phase?

 

[madkayaker]

It's been supplied with a conversion to convert to single phase. The instructions are on the lid supplied with the single phase conversion not the lid for three phase

 

[p0689109]

Motor windings

It was wired up as per the lid shown in the photo for clockwise rotation when I connected it to the terminals shown in the diagram. All links fitted, all terminals tight. Switched it on and immediate trip.

 

[madkayaker]

What size and type is the trip

 

[eil]

My opinion differs from MK in that its a single ph motor, As you have a higher resistance on Z1 Z2 than U1 U2 and very little resistance on V1 V2 which would be the centrifugal switch. If it was a three ph motor I would expect similar resistance across all windings. That fact you have resistance between the motor body and the windings would suggest a fault to earth which also bears out with the RCD tripping.

 

[rtbcomp]

What size and type is the trip

He said it was the RCD that tripped!

He also said that there was continuity between the windings and earth.

If this is the case, as I said earlier, this wants sorting before you fanny about with the links.

 

[penfold]

My opinion differs from MK in that its a single ph motor, As you have a higher resistance on Z1 Z2 than U1 U2 and very little resistance on V1 V2 which would be the centrifugal switch. If it was a three ph motor I would expect similar resistance across all windings. That fact you have resistance between the motor body and the windings would suggest a fault to earth which also bears out with the RCD tripping.

There's nothing about this motor to suggest that it's a centrifugally switched split phase; 6 contacts strongly suggests it's a 3 phase motor wired as a permanent split capacitor motor.

 

[eil]

There's nothing about this motor to suggest that it's a centrifugally switched split phase; 6 contacts strongly suggests it's a 3 phase motor wired as a permanent split capacitor motor.

You are quite right it doesn't show a centrifugal switch, but if it is wired as a PSC motor does the capacitor marked Cs stay in circuit as well as the capacitor Marked C ?. I might have made the mistake of assuming that the caps are a start and run type as its similar to one of mine which does show the centrifugal switch on the wiring diagram. Either way it has a phase to earth fault, strip it down to see whats up.
The diagram off mine

 

[p0689109]

Motor windings

Thanks lads for your replies. Now I am really confused. The diagram only shows two power cable inputs so surely its single phase. And my first thought was it was u/s when I did the resistance checks. There is a motor repairers/suppliers here in Stoke that I have used to check and confirm a motor off another machine I had and they prounounced it dead ans supplied me with a replacement at a good price. I might drop in ther to see what they think. I will update you as and when.
Regards, Michael

 

[eil]

Its not just you thats confused , do come back and update us .

 

[tigler]

Looks to me like it's a 3 phase set up to run as single phase. As 3 phase the 6 terminals can be wired for star or delta, depending on where the links are connected, then each set of 2 would have a phase connected to it.
All academic if there is a short or leak to earth though.

 

[penfold]

Looks to me like it's a 3 phase set up to run as single phase. As 3 phase the 6 terminals can be wired for star or delta, depending on where the links are connected, then each set of 2 would have a phase connected to it.
All academic if there is a short or leak to earth though.

What he said.

 

[eil]

But if it was wired in star it would have the links wired across the three poles say along the top, and if in delta it would have three links straight down and the cap from the third phase to line, and how do you disconnect the start cap out of circuit when it gets up to speed ?. I haven't seen a three ph motor wired up for single ph supply so educate me here as how it would work lads. By the way theres six terminals on my single ph motor.

 

[madkayaker]

For that three phase motor a capacitor is added into the windings (where a link should go if three phase delta) and between two windings. This introduces an electrical delay as the capacitor charges and then discharges creating the effect of rotation in the phase voltages ( as in three phase there not all live at the same time!)

 

[eil]

For that three phase motor a capacitor is added into the windings (where a link should go if three phase delta) and between two windings. This introduces an electrical delay as the capacitor charges and then discharges creating the effect of rotation in the phase voltages ( as in three phase there not all live at the same time!)

Right V2 Z1 run cap instead of link also run cap V1 Z1, no start caps involved. I have seen fan motors and such made to be run on three and single phase where you add one cap (Steinmetz) but not two. doesn't the motor have a lot less power than rated wired up like that though.

 

[madkayaker]

It does I have not come across it used on bigger motors that might be why there is the second cap to try and off set the reduction of power but I'm entering the limit of my experience now and without getting the text books out again wouldn't like to defiantly say

 

[eil]

Thanks for explanation MK, now how do they know which capacitors to use I wonder

 

[rtbcomp]

This is a 3 phase dual voltage setup



You can verify whether or not it's 3 phase by checking the symmetry of the resistances of the coils.

 

[p0689109]

Motor windings

I took a drive to the motor reconditioners today. The chap there "wee meggered" the windings and said the motor was b****ered. Could strip it down to look see but the general census is that the windings and/or the insulation had gone. He said there were definately a centrifugal switch in there as you can here it clicking as you turned the shaft. Not knowing anything about motors I just thought that was something catching, like a loose wire, which might have been causing the problem! He also reckoned that it was a single phase with the windings as per what "eil" reckoned earlier on in the thread. i.e. one loop run, one loop start and one loop for the switch.
Now I need to know the size of the motor so as to replace it to match the FIAC twin cylinder 14cfm(fad) that tigler reckons is the size of pump I got in the auction lot. He mentioned 3hp, is that the electric motor size or the air pump rating?
The u/s motors shaft dia is 24mm which is the size of the pulley the lot came with. The dimension from the centre of the shaft to the bottom of the feet is 90-91mm. That is the dimension the chap at the overhauler said was used to size the motor! From a google search that shaft diameter equates to a 1.5 or 2.2 motor!
If you can, any info would be much appreciated. Many thanks for your input so far.
Regards, Michael T

 

[rtbcomp]

Have a look on Ebay, there's a few motor suppliers and there may be a good used one to be had.

A 14cfm pump will need a 3HP motor, but if you want to run it off a 13A plug get a 2HP and fit a smaller motor pulley, of course you won't get as much air!

Is there a rating plate on the motor? That should give the HP.