Not familiar with the Colchester Student so let's hope an expert turns up soon!

I see the lathe is 415V 3-phase so take care poking around inside.

That the pump is running shows power is getting from the Clarke Converter to the lathe.

Best to start with the obvious first:

1. Are all the fuses good?

2. does the lathe have any electrical safety interlocks, and are they set correctly? Like an emergency stop button that needs to be reset, or a chuck guard that must be closed before the motor will operate, or that Limit Switch.

If all the interlocks are set, and fuses good, turning power on should operate the contactor with an audible click. The contactor is a relay containing three switches, one for each phase to the motor, probably with a fourth used in connection with the safety interlocks to prevent the motor re-starting after a power cut .

If the contactor isn't working, check the circuit that powers its coil. If the coil has power, then you need a new contactor. The broken part

may be the centre tongue from whatever this is: (I think it's the contactor)

Slightly worrying that someone has already been at the electrics.

and the missing indicator lamp:

Tempting to assume it's a major rewiring job, but it's possible it was left in running condition. Check everything obvious first. Then look for missing connections, bust contactor, broken rotary switch, or duff motor. That will involve tracing the circuit with a test meter, which is another subject.

Any Colchester owners able to positively identify the contactor? Are those fabric insulated pillars inside short wide coils thermal cut-outs that might need TLC?

Dave

Colochester lathe user has changed to https://colchesterlathe.groups.io/g/main, The manual is in the files section for download.  just thought if the coolant pump is running switch is either bridged out, or in the on position, forget that bit!

Edited By Phil Whitley on 25/11/2019 19:42:41

Hmmm, doesn't look like a rotary converter to me. A proper rotary converter uses a single phase motor to drive a 3-phase motor working as a generator. It provides a true 3-phase supply and can run multiple motors up to the total horsepower rating. The box illustrated by SoD looks more like a static converter that uses a capacitor in conjunction with the driven motor to create an artificial third phase. The give away are the switches on the front labelled in hp; used to switch in different values of capacitor for different loads. Note that a 3-phase motor will run on two phases, but is rather "lumpy". So that might be what the coolant pump is doing.

A static converter may, or may well not, run the contactors and other electrical items between the supply and motors depending upon how it is wired and the voltages required. Many 3-phase contactors run phase to phase (415V) not phase to neutral (240V).

In the absence of a 3-phase supply beg, steal or borrow a proper rotary converter. True rotary converters are pretty noisy, so you'l know if you have one!

Andrew

Richard –

Have you got a neutral connected to the switch gear – I think I'd expect the contactors to need a neutral to the coil, not be connected line to line. But if they are line to line the point above about being connected to the transformed input phases and not to the false phase is valid. What voltage is your converter actually applying, and is it three phase at all?

If you are not familiar with machine electrics that might sound like gobbledegook, so can you tell us where you are, maybe someone with the relevant expertise can assist "hands on".

Good luck, you need a competent sparks used to working with industrial machinery. Keep your fingers out of the birds nest, them wires bite!

Just looked up the PC40 manual. Its a static converter so it needs the lathe motor running to produce a reasoanble approximation to three phase.

The control gear coils must be connected across the 220 V mains input lines to work. The third leg is generated by the motor itself so no power there until its running.

Probably not man enough to run the motor properly under load but it ougth to start it off load. In my view frustration in a box. Static converters can be seriously weird devices, especially when you get much over 1 hp rating and often don't behave how the books claim.

Although, as Andrew says, rotary converters can be made as a single phase motor driving a three phase generator the term is generally understood to refer to a basic static converter driving a matched, permanently connected, three phase motor. That motor is frequently termed a pilot motor. It acts as a generator to produce the third (wild) phase leg and somewhat stabilise the voltages, currents and phase shifts of the three legs os that you can simply connect and run a machine without too much fiddling. Most boxes use an ordinary motor but, ideally a specially wound device should be used that isn't quite the same as a motor.

Most static converters can be made into an adequate approximation of a rotary converter by adding a pilot motor. Best to use a big old fashioned one rather than a modern high efficiency one. So called "Energy star" motors can be pants at this. I always used to use a motor somewhat bigger than the converter, eg add 5 Hp motor to a 3.5 static converter to make a 3 hp rated rotary.

Despite what the commercial producers like Transwave may have you believe getting things working really well is more black art than plug'n play. Seem to be lots of pertinent research papers from the wind power community about making Stienmetz (the fancy name for the circuits and wiring involved, connected devices work better. Pity none of it has made it down to affordable workshop level kit.

Clive

I suspect you may have several issues here, but I would agree with Clive, you may be on a hding to nothing with the static converter. If the pseudo third phase is not up and running and the control gear is connected to that phase, the contactor coil will never get energised. It might be worth swapping around a couple of the phases on the input to see if you can get the control gear energised. I also don't like the look of some of the old switch gear. The main contactor looks well past its sell by date. Poking around 415v if you don't know what you are doing is a dangerous sport. If you could get someone in with Electrical knowledge it would help.

For my Chipmaster, I went down the VFD route. I reused the existing forward/reverse lever and switch for the low voltage VFD control circuit.

Hi Richard, mine is definitely a Mk1, but looking at the levers on yours I would say it is a very early mk 1, I do not have the "safety apron". If you can hear the contactor pull in when you press the front lever down, and the switch for the main motor is set to on, then it should run, stupid suggestion, the chuck guard doesnt have a safety switch on it? The main contactor is pulling in, and usually the safety switches are wired into the coil circuit, but who knows if a second contactor has been added. Turn OFF and disconnect the power, and with a multimeter, see if you can test from the contactor to the reversing switch, and from the reversing switch to the motor. This does depend on whether the reversing switch is before the contactor or after it, but I suspect it is after, it is a start anyway!

Phil

Hi Richard ,yes it was plug in and play with no problems started up great in highest gear but the power started to drop of after about a year but ever so slowly, run the 3hp motor for 4 years plus so in my book that will do for me.lathe not used every day of course but 2 to 3 day on the trot was often, that's about 3hrs  a night use .

Mal

P.S the pc 40 has a trip switch as well 

Edited By mal webber on 26/11/2019 23:57:36

Edited By mal webber on 26/11/2019 23:58:49

Edited By mal webber on 27/11/2019 00:02:08

Hi Richard,

The item pictured with 3 contacts separated by grey (asbestos?) insulation panels is the contactor. The contacts don't look great. If you can hear this clunking with the start lever operation the PC40 is powering it.

Do you have a multimeter / test meter? You really need to get into some fault finding.

First thing would be to check the contactor contact resistance you can do this with it unpowered by manually closing it , pushing down on the brown (Tufnol) insulator that carries the moving contacts and then checking the resistance across each contact.

Robert G8RPI.

According to the circuit diagram the contactor has two pairs of 3 switches. One pair connects three phase to the pump and the other connects 3-phase to the main motor.

Contactors are electrically operated switches. Basically a low safe voltage is applied to a magnet coil that pulls the switch contacts together, and they do all the heavy lifting. Your contactor is very old-fashioned; everything is out in the open, making it vulnerable to damp and dirt.

Joining the dots:

1. The contactor must be working because the pump runs (you think!) However, the contactor should make a distinct 'clunk' noise when it switches on or off, and that's not been mentioned.
2. In the photo above I've labelled the switches. I guess the three on top (SW1,2,3) connect the pump. If so, the lower set connect the main motor. The rounded ends of two switch tongues can just be seen: I've labelled them Lower 1 and Lower 2. I believe the centre tongue, labelled 'Missing!' has broken off, so the motor has at least one of its 3 inputs disconnected. Given that the contacts are filthy, may be more!

Although the contactor may be of obsolete design, the control circuit is isn't! Much the same is used on modern lathe.

Modern contactors like the example above come in nice sealed boxes, rather smaller than yours, with no maintenance required. Entirely possible to replace the old contactor with a new one, the main problem being to identify one with a 240V operating coil, and six switches. They're readily available. (Ignore the annotations – they're for a single-phase motor.)

Dave

SOD, I think you are mistaken.

''According to the circuit diagram the contactor has two pairs of 3 switches. One pair connects three phase to the pump and the other connects 3-phase to the main motor.''

The Colchester diagram shows the coolant pump being started directly from the rotary switch, by 3 of the poles, the other three poles are connected to the line contactor and thermal overload and thence to the spindle motor.

Hope this helps.

Dave