A motor wiring problem

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Forum topic by NormanW posted 09-23-2014 09:52 AM 2327 views 0 times favorited 9 replies Add to Favorites Watch
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2 posts in 1342 days

09-23-2014 09:52 AM

Topic tags/keywords: motor wiring fault 220v ac

Wiring on a Chinese motor

I wonder if someone with intimate knowledge of 220V AC motor wiring can help me with a problem?

I purchased a new multi purpose woodworking machine for making mortice and tennon joints and planing timber. The machine was made in China and came from India. There is no manual although with the exception of the wiring, it is extremely robust and appears well made. Built by blacksmiths comes to mind. I have not received any assistance from the supplier, so have to figure this out on my own.

When it arrived I checked it over and found that there was just a two pin plug, no earth, with 1.5mm copper cable in a blue and a brown sheath. This looked like lighting cable and for a 2HP motor seemed inadequate.

When I looked inside the plastic peckerhead cover on the motor there are six leads, two red leads and two yellow leads that go into the motor through two different holes in pairs, and two yellow leads that go to the capacitor. Connecting the switch to the motor were four leads, two blue and two green and yellow (earth cable), and a green and yellow earth lead that was not connected to anything. There is no wiring diagram. The wiring was not well done with stray copper wire ends coming from connectors and the colours were all wrong as well.

I didn’t try the motor in this configuration. Rather, with a circuit tester I traced which wire went where, then put in a new 5 core 2.5mm cable, brown, blue, black, grey and earth from this block to the switch (and a 3 core power lead to the mains). Brown is live (one of the original blue wires), blue is return and the grey and black replace the two green/yellow leads that were present. This is as wired now.

I have taken digital photographs all along, and those below are of the original wiring configuration. In the absence of any connector identification, I have added the numbers and letters to help make sense of it.

When I turn the switch on, I get loud buzzing from the motor, but no movement. I only try it for a second or two and it doesn’t trip the RCD. The motor turns freely by hand. The switch has three buttons, green, black and red. Red returns a depressed button to off, but I suspect having drawn a circuit diagram of the wire pathways when a button is depressed that the motor direction is reversed by the black button.

At the switch there are the two wires in from the mains. There are permanent links between the mains lead connectors and the three cables from the centre connectors. The fourth cable to the peckerhead block is direct from the incoming power, so which ever button, black, or green, is pressed, power also always goes to terminal 6. This means that even when no buttons are depressed, there is a live lead at the motor which to me is dangerous.

I have replicated exactly the wiring I found, only with an earth, and normal coloured cables, but clearly something is wrong.

Dismantling the switch, there are connectors from each button which join the outer three terminals on each side with the centre three terminals, so the key appears to be where the wires lead from these centre three.

I took the capacitor out of its covering. There are two unmarked terminals at the top. In the photograph, the right lead (I call X) goes to terminal 3 on the peckarhead block. The left terminal (I have called Z) connects to terminal 5. I do not know enough about the function of the capacitor to understand what, if anything, this means. There are no leaks from it and the plastic shrink wrap seal is in good condition.

Removing the Capacitor, after discharging any residual voltage, I checked it with an analogue multi meter. Connecting the + probe to two different wires gives differing results. With ’+’ connected to wire X and ’-’ to Z, and the meter at X1K Ohms the needle immediately deflects to the end of the scale then settles back. At a second test the needle deflects 1/3 across the scale and settles back. I think this means the capacitor is OK. The capacitor is marked as 220/240 V AC, 300uF Q .

This leaves then the wiring setup at the motor. As I said at the start, I don’t know enough to know whether it is right or not. I would question whether having power always coming to terminal 6 on the peckarhead block is normal? This is a wiring layout, with original coloured wires, green button depressed.

I have tried to locate a company website but failed and although I have the machine name and number, there is nothing on the internet for it. I suspect it was manufactured some time ago, although everything was wrapped in brown wax paper, protected and greased, it just looks so 1960’s. There is a date on the engine plate of 1993.

Thanks for reading and apologies for the length, but I wanted to try and explain as muach as I could in one go. Any help would be appreciated.


9 replies so far

View ChrisK's profile


1964 posts in 3079 days

#1 posted 09-23-2014 04:04 PM

A helpful kick to the top?

-- Chris K

View runswithscissors's profile


2751 posts in 2022 days

#2 posted 09-24-2014 03:54 AM

This is so pathetic a bit of help, I’m almost embarrassed to offer it: when we travelled in Australia (where everything is 220v), I never saw a single ground connection. All outlets were 2 prong only.

I don’t understand how they get away with this. There’s obviously something I’m not grasping.

Sorry I couldn’t be more useful.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View TopamaxSurvivor's profile


18269 posts in 3673 days

#3 posted 09-24-2014 07:59 AM

Sounds like the cap is OK. Reversible single phase American motors have 6 leads. That is probably a universal motor. If so, it looks like they are reversing it swapping armature windings relative to the the field windings. It looks like the wiring diagram should work in that case. Having one side of the 220 hot all the time is common in cheaper made foreign equipment and we used to do a lot of things that way 40 years ago, but US standards have changed.

You should run a green ground wire of equal size to your power wires to the case and all metal parts.

My guess is that old machine has been setting idle for a good number of years. Moisture has possibly caused the insulation values to get low enough the motor will not start, but not low enough you are getting a direct short to blow the breaker or fuses. If it sets there humming away for very long, it could easily develop a direct short to ground through the low insulation. It is wise to keep test starts to a minimum duration.

The insulation could be tested with a mega-ohm meter. A meter like a Fluke VOM may or may not properly identify the fault if any. Sometimes, you just have to have a high voltage mega-ohm meter to get the job done.

You might try heating the motor for a few days to dry it out and see if that makes any difference.

The name plate looks like it is 220 AC 50 hz and is rated for 11.2 amps. It will probably draw about 12+ amps on 240 v 60 hz and run a little stronger than 2 hp and a bit faster than the 2800 rpm that is shown.

30 years ago I used to figure out how to make salvaged machine tools imported from all over the world run again. Usually without any diagrams for the thousands of wires running all over the place ;-( It was all 3 phase industrial equipment. This thread makes me glad I’m retired! I doubt if my brain is up to that any more ;-)) Good luck, Bob

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View NormanW's profile


2 posts in 1342 days

#4 posted 09-24-2014 05:45 PM

Dear Topmaxsurvivor

Thank you for the wisdom imparted in your response. I don’t have a high voltage ohm meter, and buying one would probably be about the cost of a reconditioned engine!

I’ll give the “dry the engine” idea a try first. I bought it as a new and unused machine. Technically I think it is. There is no indication that the wood working elements have ever touched timber. They are (still) wrapped in brown greased paper and the blades covered in wax. But based on the makers plate date, 1993, you are probably right and it has been sitting in its crate for 21 years.

I am grateful for your view that the wiring diagram looks like it should work and also that having a “hot” lead was at one time normal. I have never come across that before. Absolutely agree, it needs earthing.

One thing I had wondered about, (and the tongue-in-cheek comment from Chris K about kicking it alludes to my idea) would it be possible, as the motor turns freely, to spin it then apply power and see if that would kickstart it into life?


View TopamaxSurvivor's profile


18269 posts in 3673 days

#5 posted 09-24-2014 08:30 PM

U R welcome. I would not expect you to have a high voltage ohm meter. They are expensive enough that a professional would probably not have one for occasional use. It may be necessary to find a motor shop with one to check it out.

Giving them a spin is a common trick. Some single phase motors that develop a dead spot in the start winding can be given a bit of a spin and they will run. Using a 3 phase motor as a rotor phase to run 3 phase equipment will normally require a spin to get the idler motor going if it doesn’t have capacitors to start it.

I have never reversed a single phase universal motor, but looks like what they are doing with your machine. Like I said, I think it should work.

Good luck with the drying. Hopefully it will work. I remember a situation 40 years ago we sent a motor to the shop to get it “baked”. I may have still been an apprentice and I do not remember the circumstances. After it was dried, it ran ;-) good luck.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View TopamaxSurvivor's profile


18269 posts in 3673 days

#6 posted 10-23-2014 06:31 AM

Did you get it to work?

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Loren's profile


10385 posts in 3645 days

#7 posted 10-23-2014 06:58 AM

Could you post a picture of the machine please?

Some of these machines have reversing motors
for mortising. I have to look to tell you.

Good sites for deep insight on how to make machines
go are and -
because these sites have members who pursue
quixotic restoration efforts and succeed at it.

View Sylvain's profile


706 posts in 2497 days

#8 posted 10-23-2014 11:01 AM

- when you connect the two green wires (2) & (5) to live and the two blue wire (1) & (6) to return it should rotate in one direction;

- when you connect the green of one winding (1) and the blue of the other winding (5) to live and the other two (2) & (6) to return, it should rotate in the other direction.

I am not sure I understand the schematic of the switch; it does not seem right to me.

When the connections G-D , H-E and I-F are done, we have the first case and it should rotate

But with the connections as shown D-A, E-B and F-C, the winding with the capacitor is short circuited (D-A) and the other winding is short cicuited by (E-B). It will not turn.

After further examination,

I would connect one winding between D and E;
the other winding between F and H;

live on C and return on A.

keep the connections A-H, G-B and F-B as they are.

The winding connected to H would permanently be connected to the return via the connection H-A.
(is it right that in US the return always goes to the neutral of the distribution transformator?).

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

View TopamaxSurvivor's profile


18269 posts in 3673 days

#9 posted 10-23-2014 04:47 PM

(is it right that in US the return always goes to the neutral of the distribution transformator?).

For 120 volt circuits only, unless….....(but I won’t go there because it doesn’t apply in the shop.) ;-)

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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