As Alan has pointed out the output from a rotary converter may not be a truly balanced 3 phase supply. Try rotating the input connections to the milling machine around, u to v, v to w, w to u. If there is still a problem repeat the rotation again and see if that works.

Martin C

+1 for what Alan said about ensuring the contactor coil is connected to the 240 volt incomer leg.

Been there & dunnit a couple of times for other folk.

Clive

Some 3 ph machines are 415v only. In which case the contactor coil will be marked up 400+volts ac. If it has a 4 wire system it will be a 240v coil. Or it can have a 24v A.C or D.C coil if there is a 415/24v or 240/24v transformer in there for the control circuit. Which could be A.C or D.C depending on the control circuit power supply.

I am trying not to post answers on here electrical related because with 415v 3 ph around it could kill you without the correct electrical knowledge to fault find. I have spent my working life as an electrician, I would not like to hear about an accident by a member who is not electric savvy. If unsure find a local sparky to have a look for you.

Steve.

No Martin it is the machine that dictates what it requires not the supply if that makes sense. We used to install a lot of machinery in factories etc. Some machines would not require a neutral. So they have a power supply internal for the control or have 415v coils in the contactors. Some even had a transformer for the work light. Some machines. require a neutral. So have 240v available. They are all different. These days it is standard practice that all machinery have a 24v D.C control system. It is a minefield.

That is why I would not advice on fault finding if the op is not conversant with this sort of thing. Which from the posting I would say he is not. I am sure lots will give advice, but not a good idea.

Steve.

UK mains supply to domestic properties is live and neutral (star point of the local transformer) at 240V from a 3 phase system that is 315V phase to phase. each phase feeds one third of the properties to balance the load. If you get 3 phase to your house it will be fed by all 3 phases. If you want 415V phase to phase you would need a suitable step up transformer or have a cable put in all the way back to somewhere with a suitable supply.

Martin C

Martin

Sorry, but that is not correct.

Single phase as you say one of the three phases plus neutral, but a three phase supply is 415v between phases. Actually both could be higher or lower depending on where you are on the network and loads locally and in general.

Stuart

Ha Ha it's great to see someone else boo boo. It is usually me.

Steve.

When I lived in Dublin, I had a 3 phase supply, 415 v from the pole across the road which carried the supply to all the houses along the road.

Now that I live in the Sticks, I get my 3 phase from a Rotary Converter to run my lathe and mill ,each with 1,5 motors

However, my wood planer and spindle moulder both have 4 hp motors, but the converter has no problem handling them. Could it be that your converter is too small, although this seems unlikely.

There are rotary converters, and then there are rotary converters. The simplest (but expensive) ones use a single phase motor to drive a 3-phase motor, which generates a true balanced 3-phase output. But there are also ones that use an idler motor to generate a psuedo 3-phase output.

It would help to have more details of the mill. My universal horizontal mill also has a 5hp motor. But it also has two speed ranges. In high range the motor is wired in star and produces 5hp. In low range the windings are arranged to double the number of poles and hence halve the speed. That would normally also mean half the power. But the motor is also reconfigured to be in delta with a corresponding increase in phase current. So the power in low speed is halved due to the speed reduction but increased by root 3 due to the increased phase current giving a power of about 4hp.

If the OPs mill is similar it may be that the converter cannot supply the increased current, although nominally within it's power rating.

Andrew

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