AC motor wiring

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AC motor wiring

This topic has 13 replies, 6 voices, and was last updated 19 November 2011 at 10:37 by John Hinkley.

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11 November 2011 at 13:51 #77664
John Hinkley
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@johnhinkley26699
Here’s a question for all you electricians out there.

I have acquired a (brand new) 230V, 50/60 Hz AC electric motor. The plate on it states its speed as 2750 to 3300 rpm. It was bought to replace the broken one in my oil-fired central heating boiler – but turned out to be the wrong! However, it occurred to me that it would be ideal as a source of power for a cutter/grinder tool of the Quorn/Bonelle variety. Problem is, there are two cables coming out of the body: one three-core, black, blue and red, terminating in a plastic multi-way connector. (I assume this to be the mains connections) and the other is two-core, brown and red, with spade connectors, presumably for a capacitor. The boiler manual is no help. Can anybody help with wiring it up, please?

John
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11 November 2011 at 13:51 #5746
John Hinkley
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@johnhinkley26699
11 November 2011 at 14:36 #77665
Ian P
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@ianp
You definitely need some more information before you connect that motor to the mains. There is no particular standard for motor wiring colours but surely the boiler manual (not the ‘user guide’) will contain enough data to identify what the wires are for, if not then try the motor manufacturer.

Since the motor is most likely fairly low power, will the motor be powerfull enough for your grinder?

If you post some pictures, I’m sure someone here will be able to help.

Ian Phillips
11 November 2011 at 15:27 #77667
KWIL
Participant
@kwil
You could measure the resistance. The capacitor winding is usually much higher resistance than the running winding.
11 November 2011 at 17:07 #77671
Les Jones 1
Participant
@lesjones1
Hi John,

The first step is to see if one of the wires is the earth. Measure the resistance between the metal case of the motor and the five wires in turn. The earth will show almost zero resistance to the metalwork. (Les than 1 ohm,) The others should read a very high resistance to the case. ( Greater than 50 megohms.) I agree with Ian that some pictures would help. Also the dimensions would help to give an idea if it is powerful enough to use for a tool grinder.

Les.
11 November 2011 at 18:18 #77674
Gone Away
Participant
@goneaway
One caution: what’s the motor used for in your central heating? If it’s used for pushing air be aware that such motors are generally rated for that service … i.e. with a constant airflow over the motor which cools it. Such motors generally don’t make the best devices for workshop use.

You may (or may not) get away with light, intermittent use on grinder.
11 November 2011 at 19:26 #77684
John Hinkley
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@johnhinkley26699
Thanks for all the replies, so far. I have uploaded a photo to my album. Additional information is as follows:

Length of motor 11cm

Diameter (excluding mounting lugs) 10cm

Rated power 90W

The photo was taken with flash and the part of the label you can’t read says:

RHE 0932

R.B.L. 603SE (I believe this to be a manufacturer’s reference.)

0117

220/230V ….

On the box is the name RIELLO, through which I can get to a French web site that sells the very motor, but gives no further details.

I tried to take some resistance readings, but I think the battery in my multimeter is giving up the ghost, so I won’t give the readings until I’ve replaced it, tomorrow. Suffice to say, comparatively, the resistance between the red and brown wires, is higher, by a factor of 5, than that between the black-blue and blue-white, while the resistance between the black and white is lower still. I’m not sure whether that helps, or muddies the waters even more.

Finally, for today, the motor runs a fan, and drives the oil pump, which runs at the impressive pressure of 14 bar. Yes, 14 bar! So, I would have thought it could cope with a grind wheel!

Thanks again,

John
11 November 2011 at 19:43 #77687
Ian P
Participant
@ianp
A quick search finds lots of Riello wiring diagrams.

Without the burner model number I am just groping in the dark but the link below shows a single phase motor wired up.

A few minutes with Google should get you the exact one.

A 90 Watt motor may only be 1/8th or 1/10th HP so you will not have a lot of grunt!

Ian Phillips

http://oilburnerspares.com/products/images/pages/file/reillo%20manual/RIELLO-G2SX-3742456-424T55.pdf
11 November 2011 at 19:59 #77689
John Hinkley
Participant
@johnhinkley26699
Ian,

Thanks for the lead. One manual shows what certainly looks like my motor and has a wiring diagram, to boot. Unfortunately, the three-core wires just “disappear” into a control box, so I’m none the wiser about what to connect to what , although I’m almost 99% sure now that the spade connectors are for the capacitor. I’ll keep trawling the internet.

John
11 November 2011 at 20:00 #77690
Ed Duffner
Participant
@edduffner79357
Hi John,

The below link points to a website which has a number of Oil burners with what appear to be Riello motors. It’s in german so you might need to use google translate if you’re german isn’t up to scratch.

http://www.teucher.com/riello/

If you then select Brenner from the lefthand menu then Ölbrenner from the page. There is then a list of different burners and each of those provides a PDF document with some specifications and drawings etc (multi language). They may not have your model but worth a try in case.

Regards,

Ed.

Edited By Ed Duffner on 11/11/2011 20:02:03
12 November 2011 at 11:30 #77711
John Hinkley
Participant
@johnhinkley26699
Ed,

Thanks for your lead, too. Unfortunately, I run up against the same old problem – the three “mains” wires go to a “black box” and the mains supply comes in somewhere else. What happens in between is a bit of a black art. Surely I can just wire the blessed thing up to the mains direct, and whack a capacitor on the other two? But which wire goes where?

I’ve changed the battery in the multimeter and the resistance values for the respective pairs are as follows:

Brown to red (almost certainly the capacitor connections) 128 ohm

Black to blue 35 ohm

Black to white 13 ohm, and

Blue to white 28 ohm

Does that help? If not, I think I’ll use the motor from the spare pillar drill and crank the speed up with the pulleys.

(I should have explained that the grinder I’m intending to make will be a much simplified version, initially just to regrind end mills, which are horrendously expensive out here and cost a lot to import by post or courier from the UK.)

John
12 November 2011 at 14:20 #77717
Les Jones 1
Participant
@lesjones1
Hi John,

First I am a bit confused where the white wire comes from. In your first post you say that the three core cable has black, blue, and red wires and the two core has brown and red wires. You have only listed the resistance values between three wires. You need to list the resistance values between all of the five wires. (Unless one of the wires connects to the case of the motor in which case it will be the earth and there will be no connection to the other four wires.) From the connections shown on the web page that Ian inserted the link for one of the wires is labelled “50V” This may indicate that the main winding has a tap to provide 50 volts for the control circuitry. (It would be working like an auto transformer.)

If this is the case I would expect to find a group of three wires where the sum of two of the values added up to the third value.

Les.
12 November 2011 at 18:59 #77730
John Hinkley
Participant
@johnhinkley26699
Les,

Yes, I’m sorry. I should have written black-WHITE-blue for the three-core cable. My mistake – put it down to age and brain-fade.

Ed’s link gives a pdf file which accurately shows the motor – apparently a common driving force in many oil burners – and the wiring diagram clearly shows three wires shooting off to the control box and the other two to the capacitor. How the mains gets from the other side of the box to the motor connections is the mystery. I also saw a reference to 50V on a similar wiring diagram, but that’s the only reference to it I can find, so I’m inclined to ignore it.

Maybe I’ll connect it up to the mains, stand back and switch on. Failing that, the boiler gets its annual service next week, so I’ll ask the electrician who installed the boiler originally what he thinks.

John
19 November 2011 at 10:37 #78128
John Hinkley
Participant
@johnhinkley26699
Time to wrap this one up. The boiler’s been serviced and I asked the plumber/electrician how to wire up the motor. He confirmed that the two-core cable is for the capacitor and the three-core is the mains – blue (neutral), black and white are the live connections. He reckons that they will give two speeds. Well, I have connected it up this morning, using the capacitor from the motor that used to power the pillar dill and an RCD plug (just in case!) The result was a motor which runs the opposite way to what I wanted and appears from the sound alone to be at the same speed whichever lead is used (black or white). Whatever, neither problem is insurmountable and at least I’ve got a motor which I know can be used instead of sitting in a cupboard taking up space. Better break out the cad software and start designing a cutter/grinder!

Thanks to all who have responded to my original query.

John
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