Electric motor wiring

[midsomerdave]

I have a single phase 230V motor from an old concrete mixer. There's one of each black, white, red & green wires coming from inside. How is this connected please?

 

[brianmoooore]

Do you have a multimeter? If so, check the resistance across all combinations of pairs of wires and post the results here.

 

[snowhead]

Check on the inside of the Terminal box lid to see if there's a drawing showing terminals.
Post photo

 

[midsomerdave]

Do you have a multimeter? If so, check the resistance across all combinations of pairs of wires and post the results here.

Yep.....back soon.

 

[midsomerdave]

Hi Brian, thanks for replying

Ok....Red to Green = 3Megs
Red to Black = 16R
Red to White = 3Megs

Green to Black= 3Megs
Green to white= 25R

Black to White= 3Megs

Any ideas?

 

[midsomerdave]

Snow.....there's not even a terminal box....just wires!

 

[westward10]

Can you show a picture of the motor and it's rating plate.

 

[midsomerdave]

Hi Westward...
3 pics attached

 

[westward10]

Don't know how accurate your tests are but from your readings red to black is your main winding and green to white is the aux winding. It really needs testing correctly to ensure the windings are sound and a terminal box fitted.

 

[midsomerdave]

The two R readings were accurate, the meg readings were rising while testing, from 2 Megs up to appx. 3 Megs. I've added a pic of the terminal connector....I don't trust it and was hoping for confirmation first.

 

[midsomerdave]

Originally there was a link between the two terminals at the extreme right in the pic too.

 

[Darkwood]

Looking at the state of that it does want insulation testing as it looks like it could have had water ingress/moisture, also looks like you're missing the capacitor and TBH a small motor that size you may be looking about £80 brand new so is all your time and effort worth it?

 

[midsomerdave]

Yeah, I get what you're saying Darkwood...I already have a mixer and found this at a tip. I was hoping to get a free backup is all.

 

[brianmoooore]

Hi Brian, thanks for replying

Ok....Red to Green = 3Megs
Red to Black = 16R
Red to White = 3Megs

Green to Black= 3Megs
Green to white= 25R

Black to White= 3Megs

Any ideas?

The red - black are the connections too the main motor winding, and would connect to the mains.
To make a motor start rotating, it needs more than one phase, so a capacitor (to create a phase shift) is connected in series with a second winding (green - white).
Depending on the design of the motor, this second winding is often disconnected from circuit after the motor has got up to speed, by a switch operated by centrifugal weights on the motor shaft.

 

[Lucien Nunes]

From your tests:
Line to Red and Green
Neutral to Black and White
If rotation is in wrong direction, swap green and white.

a capacitor (to create a phase shift) is connected in series with a second winding (green - white).

As the OP measured a winding resistance between green and white, there cannot be a capacitor in series. So it is more likely a traditional split-phase motor with centrifugal switch.

 

[brianmoooore]

There's no cap. in series now, as he doesn't have the complete motor. It would have lived in the terminal box.
That's why I asked him to measure between all wires, in case there was a cap. mounted elsewhere on the motor.

 

[westward10]

I too assumed this to be split phase as the rating plate does not indicate a capacitor size although the terminal box it quite large so could house one.

 

[brianmoooore]

When the area I live in was 'electrified' only single phase was used, so most of my customers have had to manage with single phase motors. As a result I've replaced dozens of motor start and run caps. over the years, and the capacitance is rarely filled in on the rating plate. You usually have to dig out the remains of the original, and hope that the area where the rating is isn't too badly burnt to read.

 

[Lucien Nunes]

There's no cap. in series now, as he doesn't have the complete motor.

Good shout. It did seem strange to be a split-phase motor of that age and application. I had not looked properly at the pictures and misunderstood your post, which makes perfect sense.

 

[Darkwood]

I made the capacitor call on the mohassive terminal block with room for a capacitor and what seemed to be a mount for the terminal block which kept it to one side of the box.
I will put my hands up that I was just putting it out there based on that and hadn't considered a split phase as it seemed a waste of space to put a lunch box on the side of a motor for a few wires to terminate.