Colchester Student Mk1 Won’t Start

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Stuart Bridger on 13/12/2019 18:49:51:

My money would be on the converter not having enough oompf. The "phantom" 3rd phase approach of thesedevices is not ideal.

Also if it as not been run for a while, ltet it warm up for a while before trying the top speeds. It may need the oil needs warming up. When I first got my Chipmaster it wouldn't go a full pelt (3000 rpm).
There is not much that can go wrong in an induction motor, so I expect the motor is OK

A couple pages ago A guy called Mal said that he ran his colchester student on a static converter for 4 years before it gave up. He said that it slowly lost energy and ended up not being able to get into the higher speeds. Especially given that the motor is only 1.5hp with a 3.5hp converter, surely 2hp extra is more than enough?

I bought the converter from the reduced section in machine mart, so it could have been used before. It's definitely not brand new. So possibly that could be the issue, in which case i'll have to try and take it back to machine mart and get a working one?

As far as warming up goes, i'll try that tomorrow as the lathe has not been used for potentially years. ive had it since august and only just been able to turn it on.

The motor may not be the full issue, but could definitely do with some care. Its 65 years old and judging from how dirty the lathe is, It's probably full of crap too

[Phil WhitleyParticipant @philwhitley94135]

Hi Richard, the phase convertor should be fine provided it is working correctly, and I dont think the motor would turn the lathe at all if it only was getting two phases. Take the belts off, check the motor turns smoothly and freely, then power it on and see if the motor runs quietly, if it hums loudly or growls, it is likely to be off a phase or phase imbalance. let the motor run for say, ten minutes with no load on it, and see if it gets warm. Those Lancashire dynamo motors are pretty bulletproof, I doubt there is anything wrong with it. Strip the brake mechanism inside the input pulley to see if one of the brake shoes is binding, or possibly one of the linings has come unbonded and is jamming the pulley, it should be free to turn. It is possible that there is a bad bearing in the motor, but if there is, you will hear it when you run the motor without the belts on. I thought when you posted up the switch that it had been rewired to provide a straight on/off operation. No reason for it to be wired like that unless someone has tried to get the safety and key switch out of circuit, but has not understood how to do it, or not had a wiring diagram. who knows. Did you replace the missing contact in the contactor?

Phil

Edited By Phil Whitley on 13/12/2019 21:01:01

[Phil WhitleyParticipant @philwhitley94135]

we need some sound on the videos!!

Phil

[Phil WhitleyParticipant @philwhitley94135]

also noticed that you have the leadscrew and feed rod in gear, put the very short lever on the front of the headstock in the mid position and the end gears and screwcutting gearbox should stop turning. If the saddle is tightor something alse is wrong that may be why the lathe input shaft is difficult to turn, you need to find out why that is! Remeber we discussed the brake mechanism in the pulley? check it out!!

Phil

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 13/12/2019 21:01:48:

we need some sound on the videos!!

Phil

The videos should all have sound, not sure why you're not getting any. There should be a speaker at the bottom left you can click on

I had the motor out before and it seemed to be spinning fine, but I didn't leave it to run for long.

I also took the brake to pieces and its working fine.

All the safety switches have definitely been cut out of the circuit as it shouldn't run with the end cover off, but it does. There's no logical reason that they would have been taken out though, so you may be right. I still think the contactor is broken and is just being used to transfer the power, with no no-volt release. The contactor is always in contact with the circuit, it never stops being attached, so perhaps the spring went and they decided to cut it all out.

The same yellow wire from yours is disconnected at both ends on mine

I know someone who's tearing down a colchester student so even though the lathe is working for now, i'll see if i can get her to sell me the control panel and components from her lathe. So I can just replace the whole thing.

This is a video of the motor by itself and you should have audio, it runs okay, not the smoothest, but decent enough. Perhaps a little rattley, but nothing serious. I'll run it tomorrow by itself and have a play around

motor free spinning video

[Phil WhitleyParticipant @philwhitley94135]

Is that rattle at the begining of the motor running free vid the contactor chattering, or is it coming from the motor?

Phil

[Phil WhitleyParticipant @philwhitley94135]

getting a new control panel and especially if it has the later contactor, sounds like a good idea to me!!

phil

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 13/12/2019 21:27:35:

Is that rattle at the begining of the motor running free vid the contactor chattering, or is it coming from the motor?

Phil

The rattle is the noise that the converter is making. As far as i know, it should be silent, so maybe thats why there's something up

[Phil WhitleyParticipant @philwhitley94135]

Yes Richard, that definitely sounds suspicious to me, might be an idea to whip the top off and check out the capacitors to see if any of them are bulging or leaking, you get that sort of rattle from loose transformer laminations too, and they settle down as the current falls when the motor runs up to speed.

Phil

[Phil WhitleyParticipant @philwhitley94135]

Hi Richard, the videos are working with sound today, or at least some of them are , I get a 404 error on the 118 speed one but no matter. What I see on the 272 speed video tells the story, the noise from the phase convertor seems to be a relay chattering as the light flickers in time with the rattle, and then when the relay finally pulls in the motor immediately runs up to speed, and goes quiet and smooth, look in the phase convertor for loose connections or dirty relay contacts and get back to me! Watch out for the capacitors!! they hold a charge but should have discharge resistors across them. short them with a well insulated screwdriver across the terminals to discharge them and make them safe.

Phil

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 14/12/2019 14:12:56:

Hi Richard, the videos are working with sound today, or at least some of them are , I get a 404 error on the 118 speed one but no matter. What I see on the 272 speed video tells the story, the noise from the phase convertor seems to be a relay chattering as the light flickers in time with the rattle, and then when the relay finally pulls in the motor immediately runs up to speed, and goes quiet and smooth, look in the phase convertor for loose connections or dirty relay contacts and get back to me! Watch out for the capacitors!! they hold a charge but should have discharge resistors across them. short them with a well insulated screwdriver across the terminals to discharge them and make them safe.

Phil

Taken the top off the converter, I can't see anything wrong particularly. I've had issues with capacitors before so I could probably notice. My multimeter doesn't measure farads since it's just a cheap one, so I can't test the capacitance of each with that method.

It's definitely an old converter though, it's last safety test was in 2017.

I have the receipt and I have a video of it making the clunking noise. So machine Mart should just take it back with no quarrels. But it depends what people would recommend me to do next

Thanks

[Phil WhitleyParticipant @philwhitley94135]

hi Richard, have you checked that all the screws on the phase convertors contacter are tight? that is it in the last picture. you could start the lathe with the cover off the phase covertor to see if you can see anything arcing, but check all the screw connections are tight first. if the machine mart warranty covers it, I would suggest it is faulty, because the motor seems to run smooth and quiet as soon as the convertor stops rattling, and I don't think you could overload a 3hp convertor with a 1.5hp motor unless there is a poor connection through the lathe contactor, and the convertor is not consistently " seeing" all three motor windings. also check the terminals are tight on the convertor outlet socket.

phil

[Phil WhitleyParticipant @philwhitley94135]

wiring diagram corrected and made readable! this is the one for your lathe as it should be. I have taken this from the manual you downloaded to my computer, cleaned and corrected it! N/O =normally open contact. N/C=Normally closed contact.

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 14/12/2019 18:46:29:

wiring diagram corrected and made readable! this is the one for your lathe as it should be. I have taken this from the manual you downloaded to my computer, cleaned and corrected it! N/O =normally open contact. N/C=Normally closed contact.

Thanks Phil thats absolutely fantastic

The contactor in the converter is all secure and fine with the wiring. I'll try starting the lathe with the components visible tomorrow morning and get back to you

[Richard Kirkman 1Participant @richardkirkman1]

Just back in from the garage, It's very cold in there!

I've taken the top off and run the lathe. The noise seems to be coming from a small component

I've tried to get a few videos of it, you can see some little paddles working and arcing occasionally.

Mal, the man who said he ran his pc40 on his student for years, messaged me back and said that his pc 40 made these noises too when it was on its last legs. So, i'm going to take this back to machine mart and order a pc60 which he says runs everything. Should also future proof it in case i ever get any more 3 phase machinery

I'll be interested to see if machine mart has any quarrels with me taking it back

Running with top off 1

Running with top off 2

[Richard Kirkman 1Participant @richardkirkman1]

I've taken it back to machine Mart but they've got to get their 'specialist' to test it before I can have my money back

I'll wait to hear back from them, then I'll order the new one

[Phil WhitleyParticipant @philwhitley94135]

Good move Richard, until we know we have a reliable supply we are feeling around in the dark! In you video the noise is coming from the contacter in the base of the machine, and you can see the black centre of the contactor jumping in and out as it rattles, and there is also an arc from the contacts in the smaller relay inside the clear plastic box, but it does look like that convertor has been overloaded in the past, which has caused the contacts to burn and go faulty when it is loaded. Keep us all informed! Are you home for Christmas now, or still have another week at Uni?

[Phil WhitleyParticipant @philwhitley94135]

double post

Edited By Phil Whitley on 15/12/2019 15:50:21

[Richard Kirkman 1Participant @richardkirkman1]

Hi Phil, I'm now back home till around the 3rd or 4th of January. Then back to uni till the 15th when I'm back home for another fortnight after exams.

The man in the shop said the specialist would be in tomorrow so could check it at some point this week. Hopefully sooner rather than later

[Phil WhitleyParticipant @philwhitley94135]

Excellent! my feeling is that the small contactor in the plastic box, which I assume is single phase side, switches in the main contactor on the base of the unit, which is on the three phase side, it could be that servicing all the contacts in both relays would cure the problem, but not your job if it is under warranty. Also if there is some sort of overload protection in the unit, and I am sure there will be, that also could be faulty, and breaking down partially when there is load on the convertor. Having no experience with this type of phase convertor, I now realise I should have asked you to turn it on without the lathe connected, to see if it still rattled, which would condemn it as definitely faulty! No matter, we await the next thrilling installment with baited breath, and it distracts me from the triple shower and bathroom pump problem I also have on the go!

On a different tack, it could be that a fault on the lathe or the lathe wiring is causing intermittent loading on the phase convertor, and thus causing it to trip off and then restart, possible, but not probable. is the lathe contactor pulling in when you operate the lever on the lathe?, it could be that one of the contacts is not making properly. the lathe contactor must be working to an extent, because the C&D switch only completes the circuit to the coil in the contactor, and then the coil pulls the contacts in the contactor together to connect all three phases simultaeneously to the motor. Unfortunately, you cant observe this with the lid off, as removing the panel from the lathe disconnects the supply! Did you make a new contact to replace the one you found in the bottom of the box?

Phil

Edited By Phil Whitley on 15/12/2019 16:11:30

[mal webberParticipant @malwebber91786]

Hi Richard

Answer to your pm and if anyone else needs  to read up on this problem I thought It would be good to answer here yhat everyone can see ,if I can remember the pc40 use to trip out the house electrics when the suds pump run with the lathe so I just disconnected from the lathe and she run good , never got round to figure this out and have run it without suds pump ever since, still got the pc40 which runs my pillar drill 1/2 hp motor no problems bud will not run the lathe 3hp or the mill 2hp, I have tried plugging them in to the pc40 the lathe justs hums and the mill trips out the house [13amp feed ]

Richard I'am no way a electrician just giving you my experience on the clarke pc40 [ now running off a pc60 with no problems] I can take a vid or send pics if you like if it helps.

To Phill's post my pc40 rattles when nothing is plugged in and the 3 switches are on for 0.5 …1….2…hp .

Mal.

Edited By mal webber on 15/12/2019 23:20:34

Edited By mal webber on 15/12/2019 23:28:51

[Phil WhitleyParticipant @philwhitley94135]

Thanks Mal, thats interesting, possibly shows up how they fail when they do, although you would expect it to deliver its rated output reliably, but then again, it is probably made in Italy, like much of the machine mart electricals, which means some is good, and some not. I have a Clarke single phase mig from machine mart, and made in Italy, bought in the eighties, and still welding well after much use and abuse, it has had a couple of repairs, but I certainly have no complaints, and I am working on a SIP italian welder /battery charger, which is still going strong, and is suprisingly well built too!

Just a thought, did it rattle like this from new, or did it start rattling when it began going faulty?

Phil

Edited By Phil Whitley on 16/12/2019 10:47:00

[SillyOldDufferModerator @sillyoldduffer]

Posted by Phil Whitley on 16/12/2019 10:43:01:

Thanks Mal, thats interesting, possibly shows up how they fail when they do, although you would expect it to deliver its rated output reliably, but then again, it is probably made in Italy, like much of the machine mart electricals, which means some is good, and some not. I have a Clarke single phase mig from machine mart, and made in Italy, bought in the eighties, and still welding well after much use and abuse, it has had a couple of repairs, but I certainly have no complaints, and I am working on a SIP italian welder /battery charger, which is still going strong, and is suprisingly well built too!

Just a thought, did it rattle like this from new, or did it start rattling when it began going faulty?

Phil

Edited By Phil Whitley on 16/12/2019 10:47:00

I wouldn't assume the PC40 is necessarily faulty, or that replacing it with with a new PC60 will result in success!

Richard mentioned his lathe dates to 1955 and I'd have guessed earlier. The electrics appear to be original, 64 years old, and the lathe has not been kept dry. Furthermore someone has messed with the wiring, presumably in an attempt to get it going. To that I'd add the possibility that the drive train is gummed with old oil, or that new oil is stiff because of the cold weather. Maybe this adds up to more than the PC40 can cope with.

The other issue is the sort of device the PC40 is – static converters have distinct limitations! This type of converter isn't recommended for heavy or intermittent loads. From the manual:

The circuit shows the device briefly bodges an approximation of 3-phase with capacitors as a way of starting the motor. It doesn't output continuous 3-phase like a rotary converter or a VFD. The motor cannot develop full power.

Although the necessary capacitance is broadly related to the motor's output power, it's not that simple. The switches marked 1HP, 2HP and 3HP don't set power output, rather they add or subtract capacitors as necessary to match the motor to get enough phase-shift on the 3rd winding to start the motor. Page 8 of the manual shows 7 switch combinations for 0.5 to 3.5HP; the user should experiment for best starting.

Once the motor is rotating, I believe relay K1 disconnects the capacitors and leaves the motor running on two windings only. This considerably reduces the power output of the motor compared with what it would do with real 3-phase. I suggest the relay chatter is due to the PC40 thinking the motor has started and then detecting the motor is stalling, thus kicking again by reconnecting the capacitors. It's hovering on the brink of a successful start.

Note that the capacitors are only used during starting. Using this circuit for frequent stop-start work, as on a lathe or mill will shorten their working lives.

As the device is distinctly limited, they aren't suitable for all motors, or operating style. The manual says:

Thank you for purchasing this CLARKE Single to 3 Phase Converter. i.e. to run 3-phase asynchronous motors ONLY, from a 230V single phase supply.Please note that this device, because of its characteristics is for use primarily with constantly running motors. It is not desirable for use with stop start operations.

and

For some applications of small motors, or motors of unusual magnetic characteristics, it may be necessary to provide a pilot motor to obtain a balance of phases. Generally the pilot motor should be a 2 pole (2800 rpm) motor and as a general guide should be at least twice as big as the motor to be driven.

Why is the motor stalling? The PC40 must have done it's job as a starter, but maybe its autotransformer can't deliver enough amps to keep the motor turning. (A PC60 has a bigger transformer.) Or equally likely, it's because the lathe is stiff! Could be the motor would run OK on a warm day with clean bearings, but December in a clogged state is just too much. (Measuring my WM280 in a different context showed just turning its spindle, gears and leadscrew takes about 200W)

Longer term, I think a VFD would be a better solution than a PC60,. Apart from a VFD producing genuine 3-phase and getting the best out of the motor, a PC60 needs a 32A single phase supply!

Dave

[john fletcher 1Participant @johnfletcher1]

Usually there are two banks of capacitors, start and run. All in parallel when starting, then larger set disconnects connects manually or automatically when up to speed. I helped a couple friends in the past and one had a manual rotary selection switch which adjusted the run capacitors in or out. When the motor hummed along that was the correct number of caps. If it sounded right it was right.The other had a current operated relay, which disconnected all of the start capacitor when the motor was up to speed, no adjustment, all or non, type of thing. When a pilot motor was fitted things really improved. Coolant pump was wire to Delta and fitted with I think, a 4 micro farad capacitor and ran from a 13 amp socket. John

[Phil WhitleyParticipant @philwhitley94135]

Posted by SillyOldDuffer on 16/12/2019 12:57:51:

Posted by Phil Whitley on 16/12/2019 10:43:01:

Thanks Mal, thats interesting, possibly shows up how they fail when they do, although you would expect it to deliver its rated output reliably, but then again, it is probably made in Italy, like much of the machine mart electricals, which means some is good, and some not. I have a Clarke single phase mig from machine mart, and made in Italy, bought in the eighties, and still welding well after much use and abuse, it has had a couple of repairs, but I certainly have no complaints, and I am working on a SIP italian welder /battery charger, which is still going strong, and is suprisingly well built too!

Just a thought, did it rattle like this from new, or did it start rattling when it began going faulty?

Phil

Edited By Phil Whitley on 16/12/2019 10:47:00

I wouldn't assume the PC40 is necessarily faulty, or that replacing it with with a new PC60 will result in success!

Richard mentioned his lathe dates to 1955 and I'd have guessed earlier. The electrics appear to be original, 64 years old, and the lathe has not been kept dry. Furthermore someone has messed with the wiring, presumably in an attempt to get it going. To that I'd add the possibility that the drive train is gummed with old oil, or that new oil is stiff because of the cold weather. Maybe this adds up to more than the PC40 can cope with.

The other issue is the sort of device the PC40 is – static converters have distinct limitations! This type of converter isn't recommended for heavy or intermittent loads. From the manual:

The circuit shows the device briefly bodges an approximation of 3-phase with capacitors as a way of starting the motor. It doesn't output continuous 3-phase like a rotary converter or a VFD. The motor cannot develop full power.

Although the necessary capacitance is broadly related to the motor's output power, it's not that simple. The switches marked 1HP, 2HP and 3HP don't set power output, rather they add or subtract capacitors as necessary to match the motor to get enough phase-shift on the 3rd winding to start the motor. Page 8 of the manual shows 7 switch combinations for 0.5 to 3.5HP; the user should experiment for best starting.

Once the motor is rotating, I believe relay K1 disconnects the capacitors and leaves the motor running on two windings only. This considerably reduces the power output of the motor compared with what it would do with real 3-phase. I suggest the relay chatter is due to the PC40 thinking the motor has started and then detecting the motor is stalling, thus kicking again by reconnecting the capacitors. It's hovering on the brink of a successful start.

Note that the capacitors are only used during starting. Using this circuit for frequent stop-start work, as on a lathe or mill will shorten their working lives.

As the device is distinctly limited, they aren't suitable for all motors, or operating style. The manual says:

Thank you for purchasing this CLARKE Single to 3 Phase Converter. i.e. to run 3-phase asynchronous motors ONLY, from a 230V single phase supply.Please note that this device, because of its characteristics is for use primarily with constantly running motors. It is not desirable for use with stop start operations.

and

For some applications of small motors, or motors of unusual magnetic characteristics, it may be necessary to provide a pilot motor to obtain a balance of phases. Generally the pilot motor should be a 2 pole (2800 rpm) motor and as a general guide should be at least twice as big as the motor to be driven.

Why is the motor stalling? The PC40 must have done it's job as a starter, but maybe its autotransformer can't deliver enough amps to keep the motor turning. (A PC60 has a bigger transformer.) Or equally likely, it's because the lathe is stiff! Could be the motor would run OK on a warm day with clean bearings, but December in a clogged state is just too much. (Measuring my WM280 in a different context showed just turning its spindle, gears and leadscrew takes about 200W)

Longer term, I think a VFD would be a better solution than a PC60,. Apart from a VFD producing genuine 3-phase and getting the best out of the motor, a PC60 needs a 32A single phase supply!

Dave

the K1 relay switches the starting capacitors out of circuit, the running capacitors, set by the switch bank stay in. if you look at the above posts you will see the motor running both out of the lathe, and in it, turning the gearbox and chuck and in both cases, when the rattling of the contactor stops, the motor shhots up to full speed, and runs normally. From the circuit diagram above, when the motor starts, there is a voltage fed from L2 via a resistor to the rectifier which pulls K2 into the start position, and causes K1 to bring the extra capacitors into circuit. When the current falls as the motor gains speed the limiting resistor stops passing enough current to operate the rectifier, and K2 drops K1 and the extra capacitors out of circuit. In the above videos of the inside of the PC40 when operating

[Author]

Posts