3 Phase in a Model Engineers workshop

Hi All,

Sorry about this. being new to this forum stuff I am still getting my head around how it works. Hope you can see the photos. So, firstly let me say thank you all very much for replying.

However, I am more confused than ever now. I do have a basic understanding of electrics. I did get an ONC in electrical engineering but that was 50?? years ago. And I have worked as an electrician for a year, rewiring houses and stuff. So my knowledge of electrics is mostly of the domestic type. When it comes to 3 phase my knowledge is very limited. And I am well aware that 3 phase will kill you.

Looking at the photos, going from bottom to top, the first is the Transwave Rotary converter. Then comes the layout of the incoming wiring. The 3 phase distribution board is the large box on the left. The next photo is of the rotary switch on the mill. Then the push button switch and then the inside of the push button switch. Finally a picture of my Cincinnati 2M1 Universal Mill (from the hand book).

The feed to the 3 HP motor on the Lathe is 3 phases plus a neutral. The feed to the 5HP motor on the mill has only the 3 phases, but no neutral. I have measured the potential differences and on the lathe it measures 420, 440 and 460 volts between phases and 240 volts between phases and neutral. On mill the incoming feed measures 420, 440 and 460 between phases.

The isolator for the mill is a Telemecanique and is the one I used in Oxford. As it is the trip on this isolator that keeps tripping I am wondering if it is the correct type to use, but as I said I don't know enough about it. I am thinking now that I need to find an electrician who has experience in this stuff.

Cheers.

Right, thanks for the pics, the start stop buttons are just remotes so there is a contactor hiding in the machine somewhere, try tracing the wiring back or listen for the clunk to see where it comes from. You say that if you hold your finger on the start button, the breaker trips, which breaker, on the machine, on the phase convertor, or on the mains? Is it possible that the machine has gummed up with being stood, and is now taking more current than it should be? If this is the case, then the reason for the contactor holding in circuit not working could be that the overloads on the machine have already broken the holding in circuit. Any safety circuits like doors that must be closed will completely prevent the motor starting so we can rule that out (for now) Is it belt driven or Hyvo chain? Can you disconnect the drive and try to just run the motor? can you turn the machine over by hand? Is there a clutch lever that is engaged instead of disengaged? I will be on and off the net all day tomorrow if you have any more info, hope this helps

Phil

East Yorkshire https://www.youtube.com/user/philhermetic/videos

Can you take a pic of the front of the hinged lid that you show the back of pls? Cracking pics, they blow up really well!

Hi, new here but have a very similar problem.

I have a rotary phase converter rated at 4.5kW. It runs the Colchester 1800 lathe no problem but will only run my Universal mill on the low speed range (two speed motor), if I try and run it on the high speed range it won't start at all unless I take the tension completely off the belts. The mill is 2.2kW but I think the mechanical drag is just too much for it on start up.

David

The contactor is in the hinged lid, or at least it appears to be, because it is an unfamiliar type. I am intrigued by the round isolator(?) above the contactor, and also by the long earthed pin that projects from the back of the box? ot appears to operate something on the round isolator. given that you have three fairly well balanced phases at aproximately the right voltage, it looks to me like the machine is drawing excessive current because it has stiffened up, or you are trying to start it "in gear"?

Phil

East Yorkshire https://www.youtube.com/user/philhermetic/videos

Edited By Phil Whitley on 13/06/2020 21:24:13

Hi Phil,

Thanks for the quick response. You are thinking along the same lines as me. When I hold the push button in and run the machine it does make a lot of noise that I don't remember it doing back in Oxford. The clutch is definitely not engaged and the machine has been idle for about 4 years. It is belt driven (4 belts) so I will try to release them. Not easy as I have to lift the motor plate and it is flippin heavy. The pully does rotate freely by hand. As for a contactor somewhere in the machine I cant think where it could be, but I will investigate. What I really need is a wiring diagram. The manual that I have does not give one. but I Do have contact details for a Cincinnati office in the UK so I will try to contact them. The long pin, by the way is a mechanical device that stops you opening the door if the isolator is in the on position.

I really appreciate your help. Cheers.

If the isolator is tripping as you say " The isolator for the mill is a Telemecanique and is the one I used in Oxford. As it is the trip on this isolator that keeps tripping " and is the blue/grey bok on the wall (left side) I suspec that it is mis-wired. Many have a 240V coil and require a connection between one phase and neutral.

There are a few possibilities for mis-wiring. Common ones are:
Connecting coil beween phases insead of phase to neutral.
The phase the coil is connected to is not a true phase. This is less of a problem with the idler motor converter you have, but try connecting the contactor coil supply to a different phase. Note that the mis-wire could be in a number of locations.

There is also a posibility that the mill has failed electrically in storage. Possible causes are damp and rodent or insect activity. Do you have a multimeter and a insulation tester ("megger"? If so check the phase to pase resistance of the motor windings and phase to ground for motor and wiring.

Robert G8RPI.

p.s. I looked at Transwave's information on converters and was surprised how biased it was.

Hi David,
I think you should start your own thread relating to your problem. It can get very confusing discussing a number of different problems in the same thread.

Hi Tony,
I think an extra picture of the isolator door with the camera moved to the left a bit or the door swung about 30 degrees more closed might help. In the original picture I can't decide if the terminals on what I think is the contactor are in the horizontal or vertical plane. ( I think from the fact that it looks like the contactor coil is at the bottom of the picture that the contacts are in the horizontal plane.) It might also help identify the two things either side of what I think is the contactor. ( My best guess on these is thermal overload cut outs, one for the main motor and one for the coolant pump.) I think the right hand set of the four contacts on the contactor is the maintainer set to hold the coil in when the start button is released. I will avoid making any more comments at the moment as Phil seems to be thinking along the right lines and recommending sensible actions to diagnose the problem.

Les.

Edited By Les Jones 1 on 14/06/2020 09:21:39

It may be worth a look through the stuff here if you did not already know of it:

http://vintagemachinery.org/mfgindex/detail.aspx?id=2097&tab=3

Edited By DC31k on 14/06/2020 09:27:37

Are the measured phase to phase voltages off load? If so what do they measure on load, on both the lathe and mill.

Andrew

Hi All,

OK. So now I have, with some difficulty, managed to remove the belts. Not sure how the devil I am going to get them back on as when I removed the last belt the motor plate dropped to the bottom of the machine and it must weigh the best part of 2 cwt. That's a problem for later. With the belts removed I pressed the on button and the same problem. Runs for a few seconds, then stops. So it is deffinately not the machine causing the problem for which I am thankful.

The thing that puzzles me is that is running the motor from a rotary converter any different from running the motor from a 3 phase mains supply.

Looking at the inside of the hinged door, the component below the rotary switch, I am guessing is the contactor. Could this be where the problem lies.

Cheers, Tony

Is it a rotary converter or a tranverter. A rotary is a 3phase motor generater The unit you have looks like the ones with your original single phase as lets say L1 & a bank of capacitors to lead the sine wave which we will call L2, then an inductor to make the supply lag. L3. Creating artificial 3 phase. I know of 2 people who have these & watching them start there machines is weird. 1 has to hold a switch on the front panel in a certain position to get the lathe running , it buzzes like hell. Then he moves the switch to a different position to run. The artificial ones give slightly different reading on each phase. If your contactor coil is 240v then I suggest you try using a different phase. Move them twice in effect. Once reverses the motor twice back forward. I did not want to get into this. If I was there I could sort it for you. I am sure. You may kick yourself once it gets done.

Steve.

OK well that has ruled out a lot of possibles. So the motor runs, does it run smoothly and quietly, or does it run slowly and "growl" ? do you still have to hold your finger on the start button to keep the motor running, or does the contactor hold in and then trip? Is the tripping still at the wall mounted breaker? what is the HP of the mill motor and the lathe motor?

Phil

Looking at the picture of the contactor, it looks like there is two sets of overloads, the one on the left with the black wires, I am guessing is the main motor, the one on the right, with the red wires I am guessing is the coolant pump. Try running the coolant pump, and the table feed motor if it has one. Do you have a multimeter?

Phil

RTFP!

The lathe has a 3HP 3 phase motor and the mill has a 5HP 3 phase motor.

The lathe runs fine. That has a 4 wire feed, 3 phases and a neutral.

The mill motor will only run if I keep my finger on the button and it does not run smoothly at all. It sounds as though it is struggling and sounds terrible. It runs for a few seconds then stops. I then press the on button again and it does the same thing. After a few attempts at this the trip on the main isolator on the wall trips out.

The phase converter is a Transwave Rotary Converter and runs the lathe with no problem.

Anthony

Sounds to me that you need someone who knows what they are doing to be hands on with the machine, may cost a bit but at least you will be best advised.

Emgee

OK, it sounds like the motor is either off a phase, or maybe has got damp and has leaky insulation, have you tried the coolant pump/table feed to see if they run correctly? What are the earthing arrangments for the installation? If you have a multi meter you need to turn off the power, isolate the machine and start testing through each phase from the isolator on the machine, through the contactor with the contactor held in manually, through the overload, and to the motor. You could also do with a megger to do an insulation test on the motor. I think Emgee is right, we are coming to the point where you need someone on site with basic test gear to sort this out. If it was running at your previous premises, it can't be much wrong with it. there is a possibility that there is a phase off at the motor caused by a bad contact either in the contactor, , or in the overload. If the coolant/table feed works, and the main motor doesnt we have confirmed three good phases at the machine, if they don't work correctly we can suspect the supply to the machine. Incidentally, what type of lathe is it, and why does it need a neutral? Where are you in the country?

Phil

Edited By Phil Whitley on 16/06/2020 21:03:15

Right, I have just "RTFP" again and I see it is a Colchester 1800, do you know why it needs a neutral? I also see you are in the New forest! Bit too far from me in East Yorkshire, any industrial sparkies in that area read this forum?

Phil

Edited By Phil Whitley on 16/06/2020 21:19:32

Edited By Phil Whitley on 16/06/2020 21:20:18