Chipmaster power issues

Hey guys been using this website for while now been meaning to sign up for a while.

Recently bought a colchester chipmaster which is wired up for 3ph 415v. I only have a 1ph 240v supply in the workshop so i thought i would solve the problem by buying a phase converter, the clarke PC60 5.5hp converter. After wiring it all up it doesnt seem to work at all, sometime the spindle spins slowly then it cuts out, other times the contacter just pulls in then slips many times very quickly.. anyone have any suggestions?

any help is greatly appreciated.. cheers

I have not seen the Clark converter but do have two differing ways of running my machinery. The lathe has a three HP motor that is not dual wired to run 240v or 440v so that runs off a Transwave static converter of around 4.5HP capacity at the 400 volts.

My Bridgeport mill was originally wired to run off the same Transwave kit but was never happy and would stop after a short run time. This was changed to a digital inverter drive (a cheap Chinese one for around £90) the motor was changed delta to star or the other way around and runs perfectly. I did not do the wiring, that was done by a friend who knows what he is doing.

What I am saying is these things are not a plug and play, most ordinary household electricians have no idea on the three phase wiring .

You would be better going down the inverter route.. If your in the Reading area (RG7) I'd only too please to help or advise

John

The Clarke converter is a static phase converter, which AFAIK is not ideal for a lathe. The third phase is provided by a phase shift capacitor, the value of which is controlled by the switches on the front of the panel. The ideal capacitor setting will depend on the motor load, which on a lathe will not be constant. Have you tried all settings?

Also if the contactor is not holding in, then it could be that the control circuit is being fed from the "artificial" phase. The Clarke manual does cover this.

On my chipmaster I went for a VFD installation, which works like a dream, but it did require ripping out the exsiting control wiring and replacing with the low voltage DC VFD controls. Also critical here was that the original 1963 motor was not dual voltage, so I run the 415V motor with a 240V VFD uing a 29Hz base frequency setting. This was using the technique described at https://www.inverterdrive.com/HowTo/240V-Supply-to-a-400V-AC-Motor/

It might be possible to use the static converter you have already bought as a base to build a rotary converter.

Loads of info and wiring diagrams free on the net.

You have a choice of start and run capacitors. Are the switches set for your motor HP ? there is an ammeter measuring your single phase current does this show any thing? It should show a huge current when the inverter is powered (30A+?) then settle back to the running current (10-15A?).

here is a circuit diagram of it if its not in your documentation :- www.clarkeservice.co.uk/manuals2/pc20_60.pdf

Frank

Thanks for the offer, but im as far north as it gets

And thanks for the help everyone, still trying to get my head around it all. had a bit of a breakthrough tonight with the lathe though, i tried it with the converter on all setting, which puts it up to 5.5hp. the motor is 1.5hp. with all the setting on the lathe will run for about 15 seconds then the contactor jumps back out. maybe it does have something to do with the artificial phase?

When it does run, this seems about right for what the ammeter is reading. it spikes at first then seems to settle.

I am getting abit out of my depth here, but it could be an issue with the contactor. The contactor thermal overload COULD be dropping out if the phases are imbalanced, which they will be with a static converter. But 15 seconds does sound a bit quick for what is not really a fault current, just an imbalance.

Adding decent size pilot motor to make the static converter into a rotary converter always improves things. Whether it improves them enough to fix the problem is a different matter and impossible to judge without trying out. A common cause of control gear problems with converters, both static and rotary although statics are much more sensitive, is running the contactor coils via the generated phase. The generated phase is very unstable in both voltage and phase during run up. Often the variations are sufficient to cause the contactors to drop out during run up or even a short time after things should have settled down. The control gear must run via the mains supplied phases.

Sometimes the whole darn machine is sensitive to converter phase connection for no known reason. A friend has a Bridgeport connected to a Transwave rotary converter which will reliably run on only one specific order of phase connections. Wrong order = usually or sometimes runs. I had to switch the control gear transformer connections around so the contactors were happy with the same connections as the motor was. Shop gremlins playing I guess.

Over the years I've probably done over 20 static and rotary phase converter installs or sort outs. Mostly they go OK but the 4 or 5 that didn't were very hard work. One refused point blank to co-operate. That was the first time I ever used a modern VFD. Instant fan. Given the relatively small price differential converters are no longer worth the potential hassle if you do have a stubborn machine.

Clive

Just a point to clarify thing with 3 phase machines.

Most, not all are only fed by the 3 phase wires and don't have a neutral so any voltage between phases is 440v.

To operate the switch gear two phases feed a transformer that drops the voltage to a lower voltage, often 110v, sometimes 50v, sometimes 25v, depends on design. With proper 3 phase this never gives a problem as there is always 440v between any two phases.

With a static converter it takes 240v in and transforms it up to 440v and that goes out as two phases. The third phase is generated by a bank of capacitors that can be switched in and out depending on load. This phase is often called a ghost phase.

So when wiring up you need the two genuine stepped up phases to go to the two phases on the machine that are connected to the transformer. If you get one 'live' phase and the ghost phase it will not work.

TBH with modern inverter technology they are not worth it nowadays, They were and still are a cludge at best.

I recently got called out to sort a new lathe out that had been bought with a static converter and this same problem as above, got it running but it sounded like a bag of nails. This company had 3 phase in the building, juts not near the machine so I advised them to get an electrician in and wire it direct which they did and the difference was immediate. Far far smoother and quieter.

One of my friends also bought one and it was nothing but trouble, it went back 3 times after breaking down and cost a new motor to boot. When the motor went I supplied a new motor and fitted a VFD, it's still running and that has to be 15 years on.

.

Has the control panel got a transformer in it.?

If so are there various tappings for incoming voltage. Maybe connect for a lower voltage on the primary winding.

Also possible is to change the contactor and control circuit to one of a 240v rating. You could then feed the control circuit side only with a 240v supply and getting that side working without the motor connected.

However, remember that you will have 2 separate feeds to the machine so care must be exercised when working upon it. This could be best done with a master for both converter and control voltage circuit.

Nick

Some machinery needs a neutral connection, one phase and the neutral providing 220v to the control gear. Won't work with a static converter but you can fit a pilot motor and get the neutral from the star point.

Dave

Hi, This is quite interesting as it seems to be similar to whats happening with my Bridgeport (Pancake Motor) and my Transwave.

I would value any comments or advice please as my new projects are on hold until i get up and running.

thanks and Regards Vince