Cardiff Lathe Magic Smoke

[Onoff]

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)

Vaguely...got a link?

 

[Hopefuldave]

Blimey, now you're asking!

I'll have a look when I'm out the bath...

Dave H. (the other one)

 

[Hopefuldave]

Post 45 in thread "3 phase converter" has power And control diagrams and how-i-did coil winding. Hope they help rather than confuse....

Dave H. (the other one)

 

[oiltowater]

Hi Onoff,

Yes it's a rotary converter. Simple belt and braces electric parts and no 'electronics'. It gives 240 volts 3 phase. Didn't bother going to 415 volts as all my motors (and most industrial motors) rewire easily from star to delta in the junction box for 240 volts.

As a rule of thumb, the slave motor will easily run a combined motor load of up to 4 times its rating.

Well done for intending to have a go. All I would say is start. Have a decent voltmeter (that will measure capacitance) and a clamp meter for current. Layout all the bits on a sheet of plywood and hold them in place with drawing pins and hot glue. The 'bells and whistles' can follow later.

Essential Reading -Electric Motors by Jim Cox, the Workshop Practice Series No 16. This has a whole chapter on the subject.

"How to Run Three-Phase Motors on Single-Phase Power, Lindsay Publications Incorporated Inc. Small 15 page American brochure from 1987.

"10 hp Rotary Converter" by FRW 10-25-96. Found on the Net. Gives circuit, components and sources.

Len.

 

[Onoff]

Thanks to @MattH , bits received today. I dropped them off to my neighbour to fit. Hopes he sorts it pdq do I can finish my gate rollers!

I need to go and look ref fitting a VFD. I'll offer to do it and pay for the bits as a thanks for the use of it over the years.

 

[Onoff]

@MattH , evening. I'm sure there's a post somewhere where you say what vfd you used on your Cardiff lathe. Can't for the life of me find it!

 

[MattH]

@MattH , evening. I'm sure there's a post somewhere where you say what vfd you used on your Cardiff lathe. Can't for the life of me find it!

I just used a cheapo Chinese vfd. Doesn’t need to be anything special.

 

[Onoff]

I just used a cheapo Chinese vfd. Doesn’t need to be anything special.

How many HP is yours? Didn't you buy it from Amazon?

Also how do you know what parameters to set it to?

Cheers

 

[Onoff]

A bit of an update. I offered to go and have a look, not been yet mind!

He's apparently wired in one of the contactors what @MattH kindly sent. It still doesn't work. Said they were "nearly the same" and he went "wire for wire". Sounds like the A1/A2 connections might be a little different. I said I'd like to get to the motor if I came round, check it with the megger etc, "You can't, it'd mean pulling everything out!"

His idea now is to take a 230vac coil 3P contactor, feed from the converter one side and out to the motor the other. The contactor switched by the mecury switch. Says he doesnt need reverse!

You can lead a horse etc!

 

[arther dailey]

you offered , which is worth a thousand onlookers

 

[Onoff]

Just went and had a very quick look at this lathe.

He's replaced the contactor on the right with one from the assembly @MattH gave me. As I see it the RHS contactor is the main contactor. 3P comes in on the right on those 3 blues.

Feed to the motor is from the top of the (white) overload.

The 415V coil in the (main) contactor is burnt to a crisp.

There appear to be two windings on the coil, 2 black wires, measures nom 1 Ohm and two yellow, open circuit. That's thrown me, I'm only used to one coil!

Ref the motor then yes the lathe will need hauling out from against the wall to access it direct. Best I could do was measure coming out the top of the overload. I got nom. 6 Ohm between phases and on IR <2.75M Ohm each phase to earth.

Cold, tired and damp I came home. Will have another look when fresh.

On those two black "coil" wires of the burnt contactor I measured as aforementioned nom. 1 Ohm.

However... measuring between the same two blacks on the new contactor from @MattH and I get open circuit. I wonder if in fact the new coil is duff hence why it looks like it had a cable tie slapped on to hold it in? The photo @MattH sent me originally, below:

 

[Onoff]

@MattH did you have to access your motor and change to 220 delta etc?

 

[MattH]

@MattH did you have to access your motor and change to 220 delta etc?

From memory the motor was not dual voltage. I had a cracking deal on a new Brook Crompton motor so I swapped it out for a 220v motor.
Nowadays dual stage Chinese VFD’s I.e. 240v in - 415v out are cheap and readily available.

 

[MattH]

If he’s not bothered about reverse then just rip the lot out and stick a 415v DOL starter online with the motor.

 

[Onoff]

If he’s not bothered about reverse then just rip the lot out and stick a 415v DOL starter online with the motor.

What am I looking at with these original contactors, I'm assume from L to R, fwd/rev with the o'load and then the main contactor. Reckon it must be that you hear come in when you switch it on.

 

[MattH]

I might have the Cardiff manual somewhere. I’ll take a look.

 

[MattH]

 

[Onoff]

View attachment 313961View attachment 313962

Oh you star! Super grateful for that.

 

[Onoff]

From memory the motor was not dual voltage. I had a cracking deal on a new Brook Crompton motor so I swapped it out for a 220v motor.
Nowadays dual stage Chinese VFD’s I.e. 240v in - 415v out are cheap and readily available.

So your original motor was star only? Or was the star point accessible?

Really, really grateful btw for the schematic. Saves me loads of time in tracing.

 

[Onoff]

Just spent 10 minutes at the lathe owners with the voltmeter.

Turned the phase converter on. Left the lathe off.

L1 to L2 - 430V

L2 to L3 - 430V

L1 to L3 - 0V

L1 to earth - 0V

L2 to earth (machine body) - 430V

L3 to earth - 0V

He did say he may have wired it wrong...

Didn't go any further as just finished a Marston's Pedigree.