All right, I've done it now!

[4to20Milliamps]

I really can't see how many terminals it has from that picture, either way the relay coil should be on the motor side.

[Monkeh]

I really can't see how many terminals it has from that picture, either way the relay coil should be on the motor side.

No, it just has to be switched.

[4to20Milliamps]

You're probably correct, so if this schematic from the manufacturer doesn't do it I will rest my case.

http://www.kedu.cn/PDF/8/p47-48.pdf

surely one of these ways will have to work   

[Leuven]

Looking at your diagram:



If you disconnect all the motor wires from terminals 2, 4 & 6 you have the switch by itself.

Now discconnect the wire from terminal 5 and connect it to terminal 4 (in other words connect terminal A2 to terminal 4). When you press the start button a mains voltage should now appear across the relay coil between A1 and A2 and this should keep the switch latched. The relay coil current will flow from the live on A1, through the coil to A2, through the wire to 4, through the switch contact to 3, and back through the neutral wire.

With these connections the switch should click on and off. Try this and see what happens. After that we can figure out where to connect the motor wires.

I moved A2 to 4 and the switch latches on. So far so good.

I switched around 2 and 4, still buzzing.

motor on Terminals 2 and 4

I wasn't aware that his schematic was correct.....isn't that the problem?

My schematic should be close. I did write down a rough diagram so if I've got something wrong, which I did, it shouldn't be that far off.

[Leuven]

You're probably correct, so if this schematic from the manufacturer doesn't do it I will rest my case.

http://www.kedu.cn/PDF/8/p47-48.pdf

surely one of these ways will have to work   

I came across this diagram too, I think that's my switch. The problem is it looks like I have to completely re-route all wires. I would do it but I'm pretty sure it wasn't like that to begin with.

[IanB]

If you have the switch tested and working, the next step is to ignore the switch and consider the motor. If you disconnect all the motor wires and have the other wires connected according to your diagram, you will have a mains voltage at terminals 2 and 4 when you press the green button. The switch won't latch, but that does not matter right now.

What you should do is try connecting pairs of motor wires to terminals 2 and 4, press the green button and see if the motor runs. Try the following pairs:

2 : blue
4 : black
(red floating)

2 : blue
4 : red
(black floating)

Do not connect red and black to the mains or you will blow a fuse (these two wires seem to be connected internally).

If the motor does not  turn when you connect a mains voltage across the blue and black or blue and red wires, then the motor could be faulty.

[ignator]

So I have this bench grinder I was trying to clean and I've managed to mangle some of the wiring while connecting the switch back on. In retrospect, I should have been a lot more careful and write down a diagram but here I am now, and sure enough, it makes a hell of a screeching noise and no go when I turn it on now.

Any ideas what I've done wrong? I sure hope I didn't fry it. The switch is a KEDU KJD11 no-volt release.

So how is the stop button shown in any diagram?  It needs to have a contact in series with the hold coil. Did I miss this somewhere in one of the diagrams.  Also how is the start button in this circuit, I'm going to guess it's a mechanical closing of all the contacts.  I agree with Ian it's a Permanent-split capacitor motor configuration, as you indicated there is no centrifugal switch in the motor.  And this makes sense as the starting torque for a grinder is minimal (mainly just the inertia of the motor rotor and grinding wheels).

[Leuven]

If you have the switch tested and working, the next step is to ignore the switch and consider the motor. If you disconnect all the motor wires and have the other wires connected according to your diagram, you will have a mains voltage at terminals 2 and 4 when you press the green button. The switch won't latch, but that does not matter right now.

What you should do is try connecting pairs of motor wires to terminals 2 and 4, press the green button and see if the motor runs. Try the following pairs:

2 : blue
4 : black
(red floating)

2 : blue
4 : red
(black floating)

Do not connect red and black to the mains or you will blow a fuse (these two wires seem to be connected internally).

If the motor does not  turn when you connect a mains voltage across the blue and black or blue and red wires, then the motor could be faulty.

I've done that and it's buzzing both ways. I can't believe this, I haven't done anything to it but giving it a good clean inside, no wire pulling or anything rough.

I will try again and bypass the switch completely, least I could do before I scrap it.

[AlfBaz]

have you tested the cap for a short cct?
turn auto ranging off on your meter, place it on the highest ohms reading. Disconnect and short the cap terminals. place the meter across the cap terms, you should see the ohm reading climb to OL

[AlfBaz]

Oh and 13ohms between blu/blk and blu/red should yield 26ohms across red/blk.
Disconnect everything from the relay and ensure it meters as expected, at the same time re-measure the motor leads, including the cap leads with the cap disconnected

[Leuven]

Oh and 13ohms between blu/blk and blu/red should yield 26ohms across red/blk.
Disconnect everything from the relay and ensure it meters as expected, at the same time re-measure the motor leads, including the cap leads with the cap disconnected

have you tested the cap for a short cct?
turn auto ranging off on your meter, place it on the highest ohms reading. Disconnect and short the cap terminals. place the meter across the cap terms, you should see the ohm reading climb to OL

I connected the motor directly to the mains, blue/black and then blue/red as advised. Same buzzing on both, with spindle lock.

I have 2 caps here, the original and a replacement. Both measure as expected - climbing up to MegaOhms.

However, I do not get 26 Ohm across red and black, I get 0.1ohm. Does that mean short in the windings?

[Leuven]

Further measurements:

across the 2 cap wires (cap disconnected) - 49 ohm

black cap wire to motor wires:
black - 0.1 ohm
red - 0.1 ohm
blue - 13ohm

white cap wire to motor wires:
black - 49 ohm
red - 49 ohm
blue - 36 ohm

[AlfBaz]

for completeness
whats the resistance between wht cap to blk cap wire?

[Leuven]

for completeness
whats the resistance between wht cap to blk cap wire?

49 ohm, cap disconnected.

Edit: I mean across bare black and white wires, not the connectors on the cap.

[4to20Milliamps]

I know i'm whipping a dead horse, but you did say you had this thing all apart and there is no centrifugal switch on the motor?

This thing seems like it should run, your windings aren't open, they're not shorted, and your capacitor seems to be o.k.

What else is there?

[IanB]

Take a look at the permanent-split capacitor motor schematic in the link I posted before:

http://www.allaboutcircuits.com/vol_2/chpt_13/9.html

Capacitor black, motor black, motor red are the lower left terminal, all connected together. The 0.1 ohms is just meter lead resistance.

Capacitor white is the top of the capacitor.

Motor blue is the upper left terminal.

If you measure between capacitor white and motor blue, you will see one winding. If you measure between capacitor white and motor black you will see two windings (higher resistance).

It seems like everything should be good. No idea why the motor is not turning.

If you connect the mains between motor black and motor blue with the capacitor in circuit, the motor ought to turn.

[Leuven]

I know i'm whipping a dead horse, but you did say you had this thing all apart and there is no centrifugal switch on the motor?

This thing seems like it should run, your windings aren't open, they're not shorted, and your capacitor seems to be o.k.

What else is there?

Yes, I did take the 2 ends apart to replace the bearings, the 5 leads go into a bundle directly into the windings. They go into a sleeve before they get to the windings so I can't tell which one goes where but there is nothing else out there. A centrifugal switch is a big thing and I haven't seen anything remotely like that.

[ignator]

Yes, I did take the 2 ends apart to replace the bearings, the 5 leads go into a bundle directly into the windings. They go into a sleeve before they get to the windings so I can't tell which one goes where but there is nothing else out there. A centrifugal switch is a big thing and I haven't seen anything remotely like that.

Take the motor apart again, and look to see if any wires got pinched to the chassis ground.  I've had this happen to me.  Don't scrap this yet.  Trace all the wires through to windings, and see how the capacitor is connected.
Your going to make this run again.  Quick ohm meter check the ground wire to any of the motor wires, for a short.

[Leuven]

Take a look at the permanent-split capacitor motor schematic in the link I posted before:

http://www.allaboutcircuits.com/vol_2/chpt_13/9.html

Capacitor black, motor black, motor red are the lower left terminal, all connected together. The 0.1 ohms is just meter lead resistance.

Capacitor white is the top of the capacitor.

Motor blue is the upper left terminal.

If you measure between capacitor white and motor blue, you will see one winding. If you measure between capacitor white and motor black you will see two windings (higher resistance).

It seems like everything should be good. No idea why the motor is not turning.

If you connect the mains between motor black and motor blue with the capacitor in circuit, the motor ought to turn.

I think your theory of how it works is as good as it gets.

Is there something that could have compromised my measurements, such as using a standard multimeter (a Fluke nonetheless) instead of a megger?

[Leuven]

Yes, I did take the 2 ends apart to replace the bearings, the 5 leads go into a bundle directly into the windings. They go into a sleeve before they get to the windings so I can't tell which one goes where but there is nothing else out there. A centrifugal switch is a big thing and I haven't seen anything remotely like that.

Take the motor apart again, and look to see if any wires got pinched to the chassis ground.  I've had this happen to me.  Don't scrap this yet.  Trace all the wires through to windings, and see how the capacitor is connected.
Your going to make this run again.  Quick ohm meter check the ground wire to any of the motor wires, for a short.

I've checked all motor wires against the chassis ground - all sound, infinite resistance.

I will take the ends apart again and split the sleeve to see where exactly these wires go.

[Leuven]

Photos with the motor open. There are strings that hold the windings together and will have to be cut in order to get at the sleeve.

[AlfBaz]

If you connect the mains between motor black and motor blue with the capacitor in circuit, the motor ought to turn.

I agree completely

Leuven, don't cut the strings, with the motor out you should have something like the attached pic

Have you tried running it as Ian has proposed?

[Leuven]

If you connect the mains between motor black and motor blue with the capacitor in circuit, the motor ought to turn.

I agree completely

Leuven, don't cut the strings, with the motor out you should have something like the attached pic

Have you tried running it as Ian has proposed?

Your diagram checks out exactly! I will connect to the mains again to squash out any doubt.

[ignator]

Your diagram checks out exactly! I will connect to the mains again to squash out any doubt.

Did you make it go again?

[Leuven]

I've got it working, the wiring was correct all along!

There are 4 long screws that keep the ends together and what happened is all this time I kept testing it without the ends screwed on. On the other hand, the ends are held together by the bearings to begin with. Even without the screws, the rotor is perfectly centered - the aluminium stator frame has no radial play and very little axial play (maybe half a millimeter) so it didn't even cross my mind it might affect the way the motor works.

Anyway, lesson learned and a big thank you to all of you that chimed in to help. The reason I put the screws on is it was the very last thing I could do, since everything else checked out.