3 phase motor issue

[GreenGui]

For current draw on each phase just use a standard tong ammeter/multi-meter on each of the 3 phases. Presumably this was all done by the electrician installing the machine - its standard practice - I trained and worked as an industrial electrician when I left school.

 

Have you taken voltage (between each phase and earth as opposed to phase to phase) and current readings per phase at the time when the problem occurs?

[GreenGui]

The motor is running the correct way, as best I can tell. Switching the phases round to try to change the direction of rotation only results in a phase fault showing and no operation of the machine at all. That being said, the motor provides a steady RPM and with the fly wheel and conrod system on it, I don't think that it would make any difference to the machine if the motor spun the other way (assuming the power output was the same in both directions).

 

I would investigate that a bit further. Do you make that phase swap at the motor or on the connections to the machine? If on the motor, unless there is a mechanical reason that prevents the motor turning it should reverse the direction.

[Big J]

For current draw on each phase just use a standard tong ammeter/multi-meter on each of the 3 phases. Presumably this was all done by the electrician installing the machine - its standard practice - I trained and worked as an industrial electrician when I left school.

 

Have you taken voltage (between each phase and earth as opposed to phase to phase) and current readings per phase at the time when the problem occurs?

 

Yes. We've measured the current and voltage just about every single way it's possible to measure them!

[GreenGui]

Yes. We've measured the current and voltage just about every single way it's possible to measure them!

 

If that motor Mega's out OK then it can only come down to a supply issue (to the motor). Electro-mechanicals are relatively easy to check and clean etc. but if its modern electronics obviously you would need more details of how they work and a test procedure from the company supplying them.

[Billhook]

I would investigate that a bit further. Do you make that phase swap at the motor or on the connections to the machine? If on the motor, unless there is a mechanical reason that prevents the motor turning it should reverse the direction.

 

 

I would second that

[Big J]

I would investigate that a bit further. Do you make that phase swap at the motor or on the connections to the machine? If on the motor, unless there is a mechanical reason that prevents the motor turning it should reverse the direction.

 

We tried all combinations of phase swaps at the isolator for the supply for the machine. Only one sequence worked. All other sequences causes a little light within the main control box to blink at me on the phase control relay.

 

We have photographed the connections on the motor and sent it to the manufacturer and they have said that it is correct. That being said, I do think that they orientate their phases differently on the continent as every machine I've had from them has required a phase to be switched around on the supply, which we had to do with this machine as well.

[farmer rod]

Big J, Im way out of my depth with phase angle correction, but if the motor controller is electronic, then it is possible that it is limiting the electrical power to the motor as the revs decrease, motors as we all know draw more current under load, something you have is stopping that.

 

Good luck with this, what a mystery

Rod

[agrimog]

is the machine set to run on 400v, I've seen stuff from various sources where you need to make a selection for everything from 360v to 500v double check with the machine builder on the motor specs and settings

[GreenGui]

We tried all combinations of phase swaps at the isolator for the supply for the machine. Only one sequence worked. All other sequences causes a little light within the main control box to blink at me on the phase control relay.

 

We have photographed the connections on the motor and sent it to the manufacturer and they have said that it is correct. That being said, I do think that they orientate their phases differently on the continent as every machine I've had from them has required a phase to be switched around on the supply, which we had to do with this machine as well.

 

 

Presumably you refer here to the phase connections 'at the wall' so to speak. If everything after that is electromechanical then the only differences swapping phases round should make is a change in direction of the motor. That is true of 3 phase here in France as it is in the UK.

 

If however you have an element of electronic control then it may well be you have to swap over on the input as you describe. I would suggest that if that is the case the actual sine wave of the electric current might be being managed or controlled and in which case it may be that you need to also swap 2 phases at the motor. The controller being phase sensitive on the IP might also mean it is on the OP or motor load.

 

Again, the manufacturer must be able to provide you with a fault diag flow chart!

 

From the way you describe this I am beginning to doubt it is the motor:001_smile:

[Big J]

I don't think that it is the motor either. We tested the resistance this morning and it was 0.08 ohms and equal across all terminals.

 

The machine is set to run on 400v.

 

We also ran the machine with the wires switched so that the motor ran in the opposite direction. No increase in power and the saw still stalled. The manufacturer have said that they will send out a new motor on Monday, but I do not think that this will resolve the issue. Electronics I suspect - to equate it to a real work situation, it's like a car stuck in limp home mode.