Inverter question

[andrew winksParticipant @andrewwinks64215]

An often asked question but wondering if there is new news about this topic. Need to run 3 phase 415 volt sensitive drill from 240 V single phase supply. Motor is 1 hp and Y wound. What are the best options, Brisbane Australia based.

Cheers, Andrew

[andrew winksParticipant @andrewwinks64215]

[MuzzerParticipant @muzzer]

If you are planning to use an inverter (looking at the title), the easiest solution would be to reconnect the motor in delta (if that's possible). If not, you could buy an inverter that has a boost function (ie front end PFC stage) and can generate 415V from 240V single phase. If you don't want a fancy inverter with boost, you could operate the existing motor at 240V which would give reduced torque output at base speed or reduced speed at rated torque.

Bottom line is that you can't get the rated performance without the full 415V on the motor but you may be able to tolerate reduced power or speed, given that it's a sensitive drilling machine.

[Colin WhittakerParticipant @colinwhittaker20544]

To the best of my knowledge this is how things are. A three phase motor needs a three phase power supply or a three phase inverter.

If all you have is a single phase power supply then you either,

buy a single phase 240V motor or

buy a simple inverter with your motor connected in delta mode or

buy an expensive boosting inverter with your motor as wired or

even more expensively ask, pretty please, for a proper three phase power supply for your workshop.

Theoretically you might be able to bodge your motor to run on single phase with a permanent starting capacitor but that's the kind of thing that only an old wireline field engineer would do with his back against the wall.

[paul 1950Participant @paul1950]

if it's not a duel voltage motor it's going to be an expensive 415 volt inverter or a single phase motor.

[VicParticipant @vic]

Posted by Colin Whittaker on 16/04/2015 14:39:52:

Theoretically you might be able to bodge your motor to run on single phase with a permanent starting capacitor but that's the kind of thing that only an old wireline field engineer would do with his back against the wall.

That's what I did with my mill. I could only just afford to buy the mill and was going to have to get a new motor till I found out about the capacitor trick. Cost me £12 and worked fine for the couple of years I had it. Doesn't work on all motors though and if you get it wrong it could damage the motor eventually.

[John HaineParticipant @johnhaine32865]

Many if not most motors bring out the ends of the windings to terminals in the connection box on the motor, and it's trivial in this case to convert from star to delta. Then just use an inverter, they are brilliant. Look around on eBay for a good price, there seem to be a lot of surplus ones around. If you can post a photo of the connection box with the top taken off then more advice is possible. I have done two mill conversions and it was a doddle, one rewiring the motor and fitting an inverter, the other rewiring a surplus 3 phase motor and fitting it to a single phase mill.

[I.M. OUTAHEREParticipant @i-m-outahere]

Easiest is to change the motor to single phase hare and forbes will do you a unit around $200.

You are going to pay at least that for the vfd then you have to wire it up- not difficult if you have basic electrical knowledge.

230v – single phase : good points

Mechanical change over but you may have issues with the pulley bore , metric or imperial etc

Bad points :

Single speed and run more noisily than 3 phase.

3 phase + vfd good points:

Quieter running, variable speed.

Bad points:

Needs to be wired in .

So it depends on what you want as the cost will be similar either way.

[andrew winksParticipant @andrewwinks64215]

Dear all, thanks for the comments and advice! The dollars aside, I think it deserves a vfd, cheers, Andrew

[Les Jones 1Participant @lesjones1]

Hi Andrew,
If you can post a picture of the inside of the connection box on the motor it will probably be possible to say if the motor can be easily strapped for delta operation and hence the cheaper 240 volt VFD option.

Les.

[andrew winksParticipant @andrewwinks64215]

Hi Les, flying leads to a small terminal box.

[Les Jones 1Participant @lesjones1]

Hi Andrew,
Unfortunately this motor does not have all 6 ends of the windings brought out to the connection box. It looks like it should be fairly straightforward to find the star point and bring out the other 3 ends of the windings (Or just connect it permanently in delta) as the windings do not look like they have been dipped in varnish. Getting a rewind company to do it would be the safest bet. (Unless you know anyone who feels confident to do it.)

Les,

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