Cardiff Lathe Magic Smoke

[Onoff]

Whilst I was mid Covid my neighbour informed me his Cardiff lathe, similar to this one below, died on him with smoke coming out of the lower right panel where the stop/start buttons are.

I've been going along borrowing it for years. He runs it from this phase converter:

The mode of operation has always been, switch the lathe on, as you press the green start button (on the lathe) you hear a contactor/solenoid pull in behind the lower right panel. Guessing some form of NVR. The lathe isn't running at this point. Then press and hold the green Boost Button on the phase converter and start the lathe. Contactor(s) behind the lower right panel chatter like Hell initially as the lathe gets up to speed then everything settles down. You can then release the Boost Button.

I always felt that particular (chattering) contactor coil wasn't getting full voltage causing the chattering. Either that or it was getting it's full voltage but something was intermittently cutting it. There is I think in there a mercury switch somewhere.

Smoke seemingly emitted from this lower right panel area as aforementioned.

Not been along and looked yet. Any suggestions as to why this packed up on him?

Would a circuit diagram be available for this?

Cheers

 

[Pete.]

Sounds like he's got the lathe start up coil on the generated leg of the converter.

Dunno what the green button procedure is might be a means of making sure you don't try to start the lathe on 2 phases.

 

[frank horton]

Hope the lathe has some sorta clutch...what a pain in the rear to get it going....
Not suprising a machine at this age needs elec work.....
shame tho....

 

[Munkul]

I take it you can't re-pack the smoke?

I'd scrap the lot of those controls and put a nice modern inverter in.

 

[Onoff]

Sounds like he's got the lathe start up coil on the generated leg of the converter.

Dunno what the green button procedure is might be a means of making sure you don't try to start the lathe on 2 phases.

I did think that ages ago tbh.

I've never actually looked at it wiring wise. It's all fed in old colours, 1.5mm2 6243Y...

I'll try and get a good look Sunday and also at the motor plate/windings too, thinking about inverter options.

 

[fizzy]

It is now scrap - no good to anyone. I will take it off his hands

 

[MCKDAVID]

I take it you can't re-pack the smoke?

I'd scrap the lot of those controls and put a nice modern inverter in.

+1 for this, the new technology is way easier than trying to fix the older three phase converters. the price is way down too, sako ones on amazon promotions cost peanuts.

might be the easiest solution..

 

[Memmeddu]

From what I've understood it's not the PC but a contractor that has gone .
Replace it with low voltage one and install a transformer to feed all the exciting circuit

 

[MCKDAVID]

From what I've understood it's not the PC but a contractor that has gone .
Replace it with low voltage one and install a transformer to feed all the exciting circuit

you might be right, but the cost of a new 3 phase contactor, and you're well on the way to an inverter, if you add a transformer too might be the same cost..? is it worth it?, as you'll still need to run it off the phase converter, whereas with a single phase in to 3 phase inverter, you can simplify the whole system?

I know which way I'd go...

 

[Memmeddu]

you might be right, but the cost of a new 3 phase contactor, and you're well on the way to an inverter, if you add a transformer too might be the same cost..? is it worth it?, as you'll still need to run it off the phase converter, whereas with a single phase in to 3 phase inverter, you can simplify the whole system?

I know which way I'd go...

I'd choose the same road

 

[MattH]

I have the same lathe, if it has a dual voltage motor rip out all the contactor guff an pop an invertor in there. I used the two bottons to create an NVR switch to supply power to the VFD and then hooked up the switch at the end of the forward reverse rod to the 24v control side of the VFD.



That being said, I might still have the old panel with the contactors on statched away (I don't remember throwing it out).

 

[MattH]

I found it, let me know if you need the parts, I never used the lathe on 415v and it looks like the overload contactor was being held in:

 

[Onoff]

I found it, let me know if you need the parts, I never used the lathe on 415v and it looks like the overload contactor was being held in:


View attachment 310847View attachment 310848View attachment 310849

You'd be a lifesaver! PM me what you want for the parts if you would. I have to go out but just swung by and took these pics, apologies for the quality or lack thereof!

It's the contactor far right apparently that's gone t!ts up.

A bit later I'd be really interested in copying the VFD mod you did.

Thanks

 

[oiltowater]

I think you are correct that the problem that has surfaced is the NVR relay inside the lathe itself. However, I also think that the problem runs a little deeper and concerns the way the converter has been wired and installed.

You get the first phase for free from your supplier (L1). You generate the second phase by putting the first phase through a bank of capacitors (L2). The third phase (L3) is generated by the motor itself, this is often called the 'ghost phase'. L3 is only properly established when the motor is up to speed.

Contacter coils are single phase and operate with connections between two phases. If your machine has the NVR wired into the ghost leg, it will struggle until the motor is up to speed, hence all the clattering.

It is good practice to run a 'slave motor' that's under no load. Once this is up to speed, then turn on the machines. They will then see your best shot at true 3 phase.

The green 'boost' button is simply switching an extra capacitor into the second leg for start up. It helps the motor (slave or machine) come up to speed but is too much for the run condition (they will overheat), hence the temporary use.

Try changing one wire on the contacter to a different line. Consider adding a slave motor, they consume little power and considerably smooth out the three phases.

If the contacter coil has burnt out, then a new contacter will cost about £40 for a blue chip make. Be very careful about buying a cheap modern coverter. To operate anything serious expect to pay £600 - 800.

I've attached some pictures of my home built system. It runs a 2Kw lathe and a 1.5Kw grinder plus coolant pumps all at the same time. The slave motor is 1Kw. Hope this helps.

Len

 

[MattH]

You'd be a lifesaver! PM me what you want for the parts if you would. I have to go out but just swung by and took these pics, apologies for the quality or lack thereof!

It's the contactor far right apparently that's gone t!ts up.

A bit later I'd be really interested in copying the VFD mod you did.

Thanks

Just cover the postage. I can get it out on Monday with DPD for £8.
PM me your details and we can get it sorted.

 

[Onoff]

To operate anything serious expect to pay £600 - 800.

Ta. £60 - 80 sound about what I was thinking.

 

[Onoff]

Just cover the postage. I can get it out on Monday with DPD for £8.
PM me your details and we can get it sorted.

PM'd with thanks.

 

[Mick Annick]

I think you are correct that the problem that has surfaced is the NVR relay inside the lathe itself. However, I also think that the problem runs a little deeper and concerns the way the converter has been wired and installed.

You get the first phase for free from your supplier (L1). You generate the second phase by putting the first phase through a bank of capacitors (L2). The third phase (L3) is generated by the motor itself, this is often called the 'ghost phase'. L3 is only properly established when the motor is up to speed.

Contacter coils are single phase and operate with connections between two phases. If your machine has the NVR wired into the ghost leg, it will struggle until the motor is up to speed, hence all the clattering.

It is good practice to run a 'slave motor' that's under no load. Once this is up to speed, then turn on the machines. They will then see your best shot at true 3 phase.

The green 'boost' button is simply switching an extra capacitor into the second leg for start up. It helps the motor (slave or machine) come up to speed but is too much for the run condition (they will overheat), hence the temporary use.

Try changing one wire on the contacter to a different line. Consider adding a slave motor, they consume little power and considerably smooth out the three phases.

If the contacter coil has burnt out, then a new contacter will cost about £40 for a blue chip make. Be very careful about buying a cheap modern coverter. To operate anything serious expect to pay £600 - 800.

I've attached some pictures of my home built system. It runs a 2Kw lathe and a 1.5Kw grinder plus coolant pumps all at the same time. The slave motor is 1Kw. Hope this helps.View attachment 310868View attachment 310869View attachment 310871View attachment 310872

Len

Welcome, and with knowledge like that you’re going to be in demand around here.

 

[Onoff]

I've attached some pictures of my home built system. It runs a 2Kw lathe and a 1.5Kw grinder plus coolant pumps all at the same time. The slave motor is 1Kw. Hope this helps

So is yours a "rotary converter"?

I'm amassing the parts for one myself based on a bfo 110V site trannie rewound as an autotransformer. I thought the slave motor needed to be like twice the kW rating of the motor you want to run?

(I've even got 3 analogue volt meters!)

 

[Hopefuldave]

So is yours a "rotary converter"?

I'm amassing the parts for one myself based on a bfo 110V site trannie rewound as an autotransformer. I thought the slave motor needed to be like twice the kW rating of the motor you want to run?

(I've even got 3 analogue volt meters!)

Did you see mine? 3 meters for phase-phase volts, 3 for phase currents, one for input current, 10hp of idlers, 240-415 (isolating) transformer from an old Oxford oil-cooled arc welder... It's set up with interlocks on contactors so it has to go transformer - motor start - run - load just to be safe (and cos I can!)

I posted circuit diagrams of the power and control sides. It works well, feeds milling machine (3 motors, magnetic clutch/brake), hotrod bandsaw, pillar drill, inverter TIG.

Looks cool, too

Dave H. (the other one)