Ancient single phase electric motor - reversing the rotation

A

AndrewB

Morning Gents,
I hope that you can help me with this problem. I am not an electrician - I just know enough to be dangerous.

I recently bought this beautiful beast :

Drill head on.jpg

It's a Denford tools Viceroy pillar drill from the 60s or maybe even the 50s. Nice and cheap with one catch - it had a non original 3 phase motor with some strange rating on the data plate which baffled both the bloke I bought it from and my friendly electrical expert. Therefore - much as I would have liked speed control - I went the easy route and bought an ancient AEI single phase motor with the necessary – and hard to find - 5/16” shaft for a tenner.

Drill motor.jpg AEI motor data plate.jpg


Having played with the internal shimming, fabbed up a new bracket and swapped the contactor I now have a lovely working quality pillar drill for under £80. I like a bargain.

However - it goes the wrong bloody way round and as I want to make holes not fill them I'm a bit puzzled.
I swapped the L and N on the motor - no difference. A quick google tells me it must be a split phase motor - never heard of them.

So chaps - what do I (can I ?) do ?

An idler pulley is an option but a lot of faff. I can't afford any more major expense on another motor or going the 3 phase route - I want to work with what I've got.

If I open up the motor (been in there already for a once over and to free it off) can I swap the orientation of the central outer section (don't know the correct term) whilst leaving the armature and end caps in the same relative positions. I'm guessing there will be a couple of wires to swap as well although as the photo shows - the 2 supply cables are connected to the centre 'barrel' NOT the bottom end cap.

Logically - when these motors were built - they must have been designed so that they could be provided with either rotation so as to suit different applications ?

I'm sure it's not quite that simple but any advice would be appreciated.

Cheers

Andrew
 
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Nope - no capacitors externally and didn't notice any inside but then I wasn't particularly looking.

As I understand it - which isn't a lot - a split phase doesn't have capacitors.
 
This is the non original 3 phase motor that was on it - which the previous owner hadn't manged to understand or get working.

Drill motor plate.jpg

He and others told me that fitting an inverter is not an option with this motor. Can't remember if it was the STAR configuration or the 400/440 in the voltage box (i.e. NO mention of 240) that was thought to be the problem.
 
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You should be able to use inverter start on a Star motor to be honest. The inverter supercedes the need for star/delta start on a 3 phase motor

I'm no motor expert by any means and some of the more knowledgable lads may shoot me down, but what Sean posted would seem to work for me, and well what have you to loose?

Edited because I put delta instead of star
 
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I'm no expert either but isnt star wired the same as Y - most of my old 3ph machinery is either star or Y plated, and I've connected them up the same.

Can you post a picture of the windings terminations ?
 
I thought 'Star' was 'Y' - the only alternative being Delta ?

I'll do some digging tonight and see how it comes apart.
 
That old 3 phase motor doesn't have an insulation class high enough to be run on a VSD.

That being said, it could run fine for years on a vsd...

400 volt output in star will likely mean it needs 230V delta. Leave it wired in star, the vsd will come as default with a 400v output.
 
The motor is Flp (flameproof) and in the terminal box there is no access to the start winding.
To reverse this motor the start windings need to be swapped. the start winding is usually thinner and is connected to a simple centrifugal switch. The motor will have to be stripped down to access the windings.



In the above drawing i have not connected the start windings to anything just tried to explain where they need to go

Found this on youtube it shows inside the motor and the centrifugal switch can be seen

https://www.youtube.com/watch?v=Mnz82o1XYeg
 
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Not seen a vsd that is 230v single phase input and is 400v 3 phase output There may be one but its not common and suspect a heavty price tag.
most vsds output the voltage they are inputted with they just change the phase and frequency
 
mykey said:
Not seen a vsd that is 230v single phase input and is 400v 3 phase output There may be one but its not common and suspect a heavty price tag.
most vsds output the voltage they are inputted with they just change the phase and frequency
Click to expand...

VSDs with a 230V input are common as muck, and aren't a lot more money.

Just had a look, entry level 230V VSD's are cheaper.

http://www.parmley-graham.co.uk/var...e-phase/sinamics-v20-entry/6sl3210-5bb15-5av0

Obviously Siemens is one of the top end brands so cheaper will be available.
 
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Rob said:
VSDs with a 230V input are common as muck, and aren't a lot more money.

Just had a look, entry level 230V VSD's are cheaper.

6SL32105BB155AV0 / 6SL3210-5BB15-5AV0 - Siemens V20 - 0.55 kW / 3.2 A (FSA without fan), Filtered

Obviously Siemens is one of the top end brands so cheaper will be available.
Click to expand...

All correct Rob But the output on a 230v VSD is ???? and the motor is wired in star at 400v it will run but at a fraction of its power because of the reduced voltage
please check the output voltage of the VSDs 230 in =230 out 400v in =400v out

Cheers Myke
 
I'm with Rob, high dv/dt issues associated with VFD's will destroy the windings of an old motor, you can add filters but rather don't go there, it can get quite involved.

If it is a split phase motor there's two ways to reverse the direction, either you can reverse the two wires of the start winding or you can reverse the run winding. Actually there's three ways, you can also occasionally unbolt the two end caps of the motor and reverse the entire stator but this is not advisable unless you know the motor was specifically designed to do this.

To reverse the start winding you'll probably have to remove the entire termination block with the connection posts on it and look underneath it. You should see the four winding wire connections under there. To identify the start winding you'll need to resistance test both windings and the start will be the one with higher resistance.
 
mykey said:
All correct Rob But the output on a 230v VSD is ???? and the motor is wired in star at 400v it will run but at a fraction of its power because of the reduced voltage
please check the output voltage of the VSDs 230 in =230 out 400v in =400v out

Cheers Myke
Click to expand...

Output can be set to 400v with a 230v input
 
Besoeker said:
To get 400V output you would need a DC link voltage of 540V (or greater). With only 230Vac in you can't get that. Unless you add a transformer.
Click to expand...

Correct, I've never stripped one of the VSD's down. But I'd imagine they have one built in.
 
Many thanks to everyone for their input (not that I understood all of it) especially Mykey for giving me exactly the info I was after. I'm sure the drawing will become clear to me once I'm in there. Thanks also to Marvo for suggesting that turning the stator over is a possibilty - I'd rather do this than fiddle about with old soldered joints and age hardened wire and connections.
If you're all still interested I'll post some more pics of the guts when they're exposed. After that I'll decide which route to follow.
Thanks again.
 
Hmmmm. Not sure what I was expecting but probably not this.

AEI motor bottom.jpg

Firstly 2 off 20 microFarad capacitors sitting loosely in holes in the stator casting (which definitely isn't reversible).
A spring further in suggesting a centrifugal switch - yes ?
The wiring all looks to be in 'good' undamaged condition although perhaps showing its age a bit.
All the connections and screws have corrosion on them and the nut on the A2 connection was not clamping the terminal at all - almost a 2mm gap between the 2 nuts. It still appeared to run smoothly and quietly.

I'm trying to relate the above pic to Mykey's diagram but the only markings on the brown board are A1, A2, A3 and A4 so I'm still a bit stumped.
 
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Lol, I though there might be a cap somewhere, you don't often get motors that size that are split phase.

Firstly the two capacitors are wired to the same terminals so they're in parallel which means they're acting as just one big 40uF start cap, not as two individual 20uF caps.

There's almost certainly a centrifugal switch in there somewhere which will have 2 wires coming off it. Can you see where they go?
 
Hi dude,so it looks like a capacitor start motor,your capacitors seem to be paralleled up. Can you confirm a functioning switch? Was an audible "click" heard,on run up or down? It should be noticeable,on one that vintage.

If so,Mykeys drawing should be your way out.
 
Right...... I can see the switch - or parts of it - but I don't remember hearing it click when the motor started.
I can't see which wires go to it without taking the other end cap off. That will have to wait till tomorrow although I've just noticed that of the 4 wires which disappear through the hole in the casting at the top of the photo the black goes into the windings. As the red and blue are connected on the board the brown must be one side of the switch and the blue or the red must be on the other. Which means sod all to me but it might help you guys ?

The more I look at those wires the less I like them - that insulation must be 50,60 .....? years old. It's not old enough to be rubber but it doesn't look like healthy plastic. I may replace it all when (if !) I do the swap - if that's possible without interfering with the windings at all.

Still don't understand where A, Z and Z1 are on my board.
 
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At a guess its the blue and yellow (did you call it brown) but need more info. remove the other cover please
 
Sorry Mykey, now I've just re read your original post and watched the youtube clip I understand your diagram. I'll finish dismantling tomorrow and once I can see the switch and identify the 2 different size windings I think it will all become clear.

One other question - once converted I'll be running it on the 'starter' winding. Presumably this won't be a problem on a pillar drill but would be on something like a lathe where it runs continuously for sustained periods ?
 
The start winding just starts it running then is switched off by the centrifugal switch if done correctly the motor will run at full power.
If the start winding was not there you could spin the shaft forward and it would run forward or conversly spin in reverse and it will run in reverse. The start winding just starts it spinning.
please post back before altering wiring as the caps if shorted will go off like a shotgun.
 
the start winding only runs on start up to provide a phase rotation. . then the centrifugal switch kicks it out.
 
To clarify, what you need to achieve is to reverse the polarity of one winding relative to the other. It does not matter which one you reverse because their polarity relative to the mains supply is immaterial. All you need to do is identify the two leads belonging to one of the windings and interchange them.

If you can identify four leads from the windings, by disconnecting them and checking for continuity between them you can make them up into pairs. E.g. if you call them 1,2,3 & 4, and you have continuity from 1 to 2 (one winding) and from 3 to 4 (other winding), then reconnect leads 1 & 2 whence they came but interchange 3 with 4. I would expect Red/Black to be the run winding, and Yellow/Blue to be the start winding, with the starting switch internally connected in series with one of those leads. In this case, interchanging blue and yellow will reverse the motor, but you should do the continuity check and try to follow the leads in case my assumption is wrong.

The start winding and run winding retain their original functions, but the phasing of their currents is inverted so as to produce a magnetic field that revolves in the opposite direction. Once up to speed and the centrifugal switch opens, the motor carries on running in whichever direction it is already running.

E2A: Have you looked inside the covers you have removed? There is often a wiring diagram stuck on the inside.
 
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AndrewB said:
.......The more I look at those wires the less I like them - that insulation must be 50,60 .....? years old. It's not old enough to be rubber but it doesn't look like healthy plastic. I may replace it all when (if !) I do the swap - if that's possible without interfering with the windings at all....
Click to expand...
Don't worry about the insulation, it's normal for it to look tatty and go hard because the heat from the motor takes its toll over the years. Don't try to replace the wires, just use a couple of layers of heat shrink sleeving if there's areas where it's cracking.

As lucien says the name of the game now is to figure out the 3 pairs of wires for the start winding, run winding and centrifugal switch. If you separate out all the wires and measure the resistances I'd expect the start winding to be around 15 ohms, the run winding maybe about 5 ohms and the switch will either be infinite or zero resistance depending if it's open or closed but I'd expect the latter if the motor is stationary unless it's sticking. Please note the values given are a very rough guide and could even be 50% out.
 
Thanks Lucien - you are correct.

Motor 4 wire colours.jpg

I removed the armature, the board and the two capacitors and I then get continuity across red and black but nothing across yellow and blue until I close the switch - which is hidden behind the casting.

I've sketched out the circuit as it was so I think I can now work out the rest. I'll check on here first though before I blow myself up.

Thanks again.

Edit - Marvo - heatshrink ! Thanks, hadn't thought of that.
 
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AndrewB said:
Thanks Lucien - you are correct.


I removed the armature, the board and the two capacitors and I then get continuity across red and black but nothing across yellow and blue until I close the switch - which is hidden behind the casting.

I've sketched out the circuit as it was so I think I can now work out the rest. I'll check on here first though before I blow myself up.

Thanks again.

Edit - Marvo - heatshrink ! Thanks, hadn't thought of that.
Click to expand...

Looks like its plain sailing now rebuild it but swap the positions of the blue and yellow over. Do let us know how it drills. :grin:
 
mykey said:
swap the positions of the blue and yellow over.
Click to expand...

Aaaahh the penny has finally dropped - this will change the direction of the current through the starter winding and the corkscrew rule thingy - or is it Flemings Right hand Rule (??? ...A Level physics was a long time ago) then means that the rotation is in the opposite direction, yes ? After that - as several people have said - the run winding takes over.

OK, heatshrink, bit of cleaning up connections and then reassemble. Photos to follow.
 
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change the direction of the current through the starter winding and the corkscrew rule thingy (??? ...A Level physics was a long time ago) then means that the rotation is in the opposite direction, yes?
Click to expand...

Sort-of. The winding current is AC so it reverses 50 times a second anyway, what you are changing is the timing of the reversal of the start winding current relative to the run. The different characteristics of the two windings, and the presence of the capacitors, mean that when they are both connected to the same supply their currents will differ in phase by about 1/2 pi electrical radians, corresponding to their electrical angular displacement in the stator slots (on a 4-pole motor that's half the mechanical angle). Over one mains cycle you might get in sequence S- R+, S+, R- so a notional + seeking point on the rotor will follow from R to S around the stator. Reversing S will give S+, R+, S-, R- so the same point will now follow from S to R, developing torque in the other direction.
 
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AndrewB said:
Thanks Lucien - you are correct.

View attachment 31530

I removed the armature, the board and the two capacitors and I then get continuity across red and black but nothing across yellow and blue until I close the switch - which is hidden behind the casting.
Click to expand...

Did you test each wire to every other wire? What was the resistance you saw yellow-blue?

When you removed the termination block where were the two power wires connected to underneath?

From the info so far your circuit should be something like this I think.

Motor.jpg
 
Marvo said:
Did you test each wire to every other wire? Yes - no continuity except those above.

What was the resistance you saw yellow-blue? 29.5 Ohms, Red Black was 5.5 Ohms.

When you removed the termination block where were the two power wires connected to underneath?
The one at A4 went to A3 (the red/blue stud) and the black went to the bottom left stud - the one with the black going off to the winding.

From the info so far your circuit should be something like this I think.

View attachment 31534
Click to expand...

You blokes are too clever ! I think that's what I've got - but clearer !
 
AndrewB said:
Marvo said:
Did you test each wire to every other wire? Yes - no continuity except those above.

What was the resistance you saw yellow-blue? 29.5 Ohms, Red Black was 5.5 Ohms.

When you removed the termination block where were the two power wires connected to underneath?
The one at A4 went to A3 (the red/blue stud) and the black went to the bottom left stud - the one with the black going off to the winding.

From the info so far your circuit should be something like this I think.

View attachment 31534
Click to expand...
You blokes are too clever ! I think that's what I've got - but clearer !
Click to expand...
From the info you've given the drawing I did should be correct.

The end is in sight, you should be able to reassemble it exactly as it came apart and just reverse the black and the red wires that go to the windings to achieve reverse rotation. Obviously sleeve any wiring that needs it and check the terminations are all good , tight and none are frayed. Make sure you don't trap any wires, it's a common issue when reassembling motors. Using cable straps to truss everything up nicely helps avoid this.

When you test it some things to watch for;

  • Start up of the motor should be crisp and you'll probably hear the centrifugal switch operate with a click almost instantaneously. If it's slow to start or there's humming/buzzing then disconnect immediately.
  • When power is disconnected it should coast slowly to a stop and you'll hear the centrifugal switch operate when the rotation speed gets low.
  • If the motor has a running current marked on it check the supply with the motor running using a clamp on ammeter. I'd think the running current should be around 50% of the stated value if there's no load on the motor. If the actual run current is greater than or almost equal to the current stated on the motor there's a problem and disconnect quickly before the windings get burned.

I'd strongly recommend you test the motor using a supply from a socket that's fed from an RCD in the consumer unit. If your CU doesn't have an RCD then maybe invest in a piggyback type RCCB that plugs into the socket first. Make sure the earth wire of the supply is connected to the steel frame of the motor and don't manually hold the motor whilst testing. Be safe.

PlugInRCD.jpg
 
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Right Gents, wires swapped and re-assembled up to this stage.

Photos show before and after - hard to get it wrong really (famous last words) with all the excellent instructions.
I've not wired the capacitors back in exactly the same way as before - is it significant ? They're still in parallel.

AEI motor bottom.jpgPICT3568.jpg

If you're all happy I'll finish off tomorrow.

Thanks and regards.

BTW - there weren't any wiring diags inside the end covers.
 
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