Electrickery

[twentysix by twentyfive]

@Tenkaykev It seems it's not as old as 100 yrs . The Lathe is from Axminster Power Tool Company. There's a label on the motor which says it's an Induction Motor, 0.5 kW, 4 A, 240 V, Single Phase, 4 pole, 1420 rpm and the date has been changed from 1991 to 1992 (I assume the up date reflects the sales date while the earlier is the manufacture date?) There's a Serial Number _Y0700 where the " _ " is unreadable.

Feeling a bit shattered at the moment so reluctant to play with live mains "out in the open" . Tomorrow is another day.

 

[MrGrumpy]

Those wires are the input cable to the mains plug and the output to the motor

There is and I've checked. Very old model it is and no spares.

I put mains directly on the input wires and pressed Green. Nothing. I was expecting to maybe hear the relay clunk over and maybe see some volts at the output. But nothing.

My next move is to bypass the Green button to see if that's any better. And maybe try to test the coil continuity.

When your less tired , maybe get the meter on those connections and check your getting voltage. Need to trace this out. Thought you had some modern contactor but it’s ancient ! Same principle with the relay though.

 

[twentysix by twentyfive]

When your less tired , maybe get the meter on those connections and check your getting voltage. Need to trace this out. Thought you had some modern contactor but it’s ancient ! Same principle with the relay though.

Yep - attempting to work my way through. Was hoping to do it with battery volts from the meter but playing with live mains seems to be necessary. Need my A game when playing with live mains.......

 

[twentysix by twentyfive]

Update

Checked the continuity of the coil. Seems it's open circuit. Which would explain quite a bit. Still confused about the on/off buttons tho'. Not that that matters now as I need a new shebang. Think I'll ask Axminster Power Tools first. Unless any of the experts on here know what's available that would suit.

Cheers all.

 

[Tenkaykev]

Update

Checked the continuity of the coil. Seems it's open circuit. Which would explain quite a bit. Still confused about the on/off buttons tho'. Not that that matters now as I need a new shebang. Think I'll ask Axminster Power Tools first. Unless any of the experts on here know what's available that would suit.

Cheers all.

There’s several ways of wiring starting switches, depending on the connections on the terminal board which will be under a small cover plate on the non drive end of the motor. I’d see if Axminster can be of any assistance.

 

[twentysix by twentyfive]

There’s several ways of wiring starting switches, depending on the connections on the terminal board which will be under a small cover plate on the non drive end of the motor. I’d see if Axminster can be of any assistance.

I've got a roughly drawn circuit diagram now which, if I can tidy it up I may post. As far as I can understand these switches aren't wired beyond the circuit board. Also the thing that puzzles me is that the tiny tiny wires of the coil (inside the relay) are energised by the full mains. Or is there some mitigation applied in the depths of the switches? It can't be this difficult can it?

 

[Tenkaykev]

A

I've got a roughly drawn circuit diagram now which, if I can tidy it up I may post. As far as I can understand these switches aren't wired beyond the circuit board. Also the thing that puzzles me is that the tiny tiny wires of the coil (inside the relay) are energised by the full mains. Or is there some mitigation applied in the depths of the switches? It can't be this difficult can it?

Inside the motor there should be a terminal board . The Main or “ Run “ windings are usually labelled “ A” and “ AA” ( or “ A1and A2” )
Start windings are Z and ZZ .
For a fixed rotation motor they usually “ Common “ for example A1 and Z1 on one terminal post which is where one of the mains is connected. The other mains is connected to the other “ A2 “. From there the power will travel through the start windings, capacitor and centrifugal switch before returning through a link to a separate post on the terminal board and linked back to A2.
When you apply the power it travels through the Run windings, and temporarily through the start windings, capacitor and centrifugal switch. When the motor is at approximately 75% of full load speed the weights on the centrifugal switch throw it open to protect the capacitor and start windings. When you switch the motor off, the springs on the centrifugal switch cause it to re engage ready for next time.

 

[twentysix by twentyfive]

A

Inside the motor there should be a terminal board . The Main or “ Run “ windings are usually labelled “ A” and “ AA” ( or “ A1and A2” )
Start windings are Z and ZZ .
For a fixed rotation motor they usually “ Common “ for example A1 and Z1 on one terminal post which is where one of the mains is connected. The other mains is connected to the other “ A2 “. From there the power will travel through the start windings, capacitor and centrifugal switch before returning through a link to a separate post on the terminal board and linked back to A2.
When you apply the power it travels through the Run windings, and temporarily through the start windings, capacitor and centrifugal switch. When the motor is at approximately 75% of full load speed the weights on the centrifugal switch throw it open to protect the capacitor and start windings. When you switch the motor off, the springs on the centrifugal switch cause it to re engage ready for next time.

Thanks. I haven't penetrated quite as far as that. I have replaced the start capacitor (which has it's wires poking through a hole in the motor housing) in the past and I've seen the centrifugal switch operating at the non drive end as that cover comes off easily so your description makes much sense.

I've tidied up my attempt at the circuit diagram a bit and I've missed something. The power to the motor from the circuit board appears to have no feed at all . This is clearly rubbish so I had a closer peer at it all and couldn't see how it is connected. I did notice that it might be possible to pull the plastic cover away from the relay which might provide a better look at the connections in there and at the coil/switches. I feel more tinkering coming on.

Meantime I've contacted Axminster with all the details so I await a response.

 

[Tenkaykev]

Thanks. I haven't penetrated quite as far as that. I have replaced the start capacitor (which has it's wires poking through a hole in the motor housing) in the past and I've seen the centrifugal switch operating at the non drive end as that cover comes off easily so your description makes much sense.

I've tidied up my attempt at the circuit diagram a bit and I've missed something. The power to the motor from the circuit board appears to have no feed at all . This is clearly rubbish so I had a closer peer at it all and couldn't see how it is connected. I did notice that it might be possible to pull the plastic cover away from the relay which might provide a better look at the connections in there and at the coil/switches. I feel more tinkering coming on.

Meantime I've contacted Axminster with all the details so I await a response.

If you are poking about make sure the plug is out of the wall. If you look at the relay it looks like there are a couple of black tabs in the transparent casing. Pushing them in should allow you to remove the cover of the relay and see where the very fine wires from the solenoid coil are attached. You can then check for continuity. If the coil is open circuit then you will need a new relay.
EDIT: If you send me your circuit diagram I can see if I can make sense of it.

 

[twentysix by twentyfive]

If you are poking about make sure the plug is out of the wall. If you look at the relay it looks like there are a couple of black tabs in the transparent casing. Pushing them in should allow you to remove the cover of the relay and see where the very fine wires from the solenoid coil are attached. You can then check for continuity. If the coil is open circuit then you will need a new relay.
EDIT: If you send me your circuit diagram I can see if I can make sense of it.

Thanks @Tenkaykev . I got the plastic cover off and tried to find continuity through the coil. The little wires may be coated with insulation stuff maybe so I ended up on where they had been soldered on for a good contact. No continuity. The relay switches themselves move freely when pushed and I get continuity through those when held closed. So it seems it's the coil

For completeness I checked my original circuit diagram and realised I had drawn the relay switches between the wrong pins. With the cover off this was obvious so here's what it looks like now. All very understandable I think.

So thanks @Tenkaykev and @MrGrumpy for your assistance and patience with this old fart who's brain is turning to mush. Perhaps one last question if I may be so bold. Any thoughts on where I could source a suitable replacement (should Axminster PTC fail me)? What am I asking for?

 

[Tenkaykev]

Thanks @Tenkaykev . I got the plastic cover off and tried to find continuity through the coil. The little wires may be coated with insulation stuff maybe so I ended up on where they had been soldered on for a good contact. No continuity. The relay switches themselves move freely when pushed and I get continuity through those when held closed. So it seems it's the coil

For completeness I checked my original circuit diagram and realised I had drawn the relay switches between the wrong pins. With the cover off this was obvious so here's what it looks like now. All very understandable I think.
View attachment 610816

So thanks @Tenkaykev and @MrGrumpy for your assistance and patience with this old fart who's brain is turning to mush. Perhaps one last question if I may be so bold. Any thoughts on where I could source a suitable replacement (should Axminster PTC fail me)? What am I asking for?

Ah, so just Live and Neutral out to the motor? Fixed rotation then.
This should do the trick. It wont fit in the existing start location but it is self contained. You would need to set the overload current to the nameplate current on the motor ( usually a slider or dial inside the contactor )

I would STRESS that you should get a suitably qualified electrician to carry out the work ( over the years we " lost " a couple of competent guys who were fully qualified but got distracted and electrocuted themselves 😢)

https://www.electrotechdrives.co.uk...red-with-2-5-to-4-amp-overload-0-55kw-0-75hp/

 

[twentysix by twentyfive]

Ah, so just Live and Neutral out to the motor? Fixed rotation then.
This should do the trick. It wont fit in the existing start location but it is self contained. You would need to set the overload current to the nameplate current on the motor ( usually a slider or dial inside the contactor )

I would STRESS that you should get a suitably qualified electrician to carry out the work ( over the years we " lost " a couple of competent guys who were fully qualified but got distracted and electrocuted themselves 😢)

https://www.electrotechdrives.co.uk...red-with-2-5-to-4-amp-overload-0-55kw-0-75hp/

Thanks again @Tenkaykev . Looks like the cable routing will need to be totally changed as the current housing is probably too small/wrong shape if using the above. So I'll get a "man who can" in. I had to make a new "blister" to accommodate the replacement starter capacitor in a safe fashion. Drainpipe is a good insulator. You'd think over the years the capacitors would have gotten smaller.

 

[Tenkaykev]

Thanks again @Tenkaykev . Looks like the cable routing will need to be totally changed as the current housing is probably too small/wrong shape if using the above. So I'll get a "man who can" in. I had to make a new "blister" to accommodate the replacement starter capacitor in a safe fashion. Drainpipe is a good insulator. You'd think over the years the capacitors would have gotten smaller.

Electrolytic or "Starter " capacitors don't like it up em! they go pop, often quite spectacularly if left connected to mains power for more than a few seconds. The actual capacitance isn't critical ( they often have a value range printed on them, " 80 -100 Mfd " for example.
Run Capacitors are designed to be permanently connected while the motor is running. Sometimes the run capacitor will be switched internally in the " Run " position to be in series with the start windings. ( this is more efficient as the start windings are usually disconnected once the motor is up to speed ) It is ok to substitute a " Run " capacitor of the same value as the Start Capacitor but not vice versa, though run capacitors tend to be a lot bigger physically. Run capacitors also need to be rated at 450V or thereabouts as that electrickery is alternating, + / - 220 volts above and below 0 volts.

 

[Tenkaykev]

Thanks again @Tenkaykev . Looks like the cable routing will need to be totally changed as the current housing is probably too small/wrong shape if using the above. So I'll get a "man who can" in. I had to make a new "blister" to accommodate the replacement starter capacitor in a safe fashion. Drainpipe is a good insulator. You'd think over the years the capacitors would have gotten smaller.

Some motor manufacturers save money ( and physical size ) by fitting start capacitors that are rated for 120 Volts. They get away with this by tapping into the internal mid point connection of the starting winding . In your 4 Pole motor there are four groups of Run winding coils arranged around the core. If you imagine a clock face the main run winding coil groups will be at 12 - 3, 3-6, 6-9 and 9-12, with the start winding coil groups spanning them ( 1:30 - 4:30 etc )

 

[twentysix by twentyfive]

Some motor manufacturers save money ( and physical size ) by fitting start capacitors that are rated for 120 Volts. They get away with this by tapping into the internal mid point connection of the starting winding . In your 4 Pole motor there are four groups of start winding coils arranged around the core. If you imagine a clock face the main run winding coil groups will be at 12 - 3, 3-6, 6-9 and 9-12, with the start winding coil groups spanning them ( 1:30 - 4:30 etc )

The grey one was fitted by the manufacturer in 1991/2 I believe. It died so I've been running the black one since. You'll see that it's a smaller capacitance value but is longer and slightly bigger diameter. The "worry" I had when I bought it (as a start capacitor) was that the quoted life was (I thought) quite short. So I bought two. So far so good tho' on that side of things.