Emco Mentor Mill conversion

[Lee Roberts]

Nice to see you back Ross, was reading some of your threads the other day and said to myself "i wonder what hes upto these days".

.Me

[Swarfing]

If there is no obvious opening or cap to reconfigure then maybe not? google mot or details and see what comes up.

[GEOFFREY]

I think you probably can still reconfigure it , but you will need to find the star point on the windings and the rewire as delta. G.

[m_c]

Whether the motor can be altered to run on 240V depends on if it's wired as Star or Delta 440V.

It's a case of carefully dismantling the motor, and seeing where and how the coils are connected. If all the coil wires ultimately end up with 3 going to the power feed, and 3 joined together in at one point, it can be changed to run on 240V. However, if each of the three going in split to two, then it's already in delta and can't be changed.

[GEOFFREY]

Absolutely correct m_c, I assumed the motor is probably wired as star which is why I said it can "probably" be reconfigured to delta. If it is already delta then there is no "simple" solution. G.

[m_c]

Absolutely correct m_c, I assumed the motor is probably wired as star which is why I said it can "probably" be reconfigured to delta. If it is already delta then there is no "simple" solution. G.

From my experience, if a motor is 240V capable it will be written/stamped on the plate as being capable of dual voltage. However if it's wound for 415V in delta, it will most likely be marked as 415V only.
However, until you dismantle it and check how the external wiring links to the coil wires, you can only make a guess.

There are a couple options to avoid a motor swap. If you can live with reduced torque at higher speeds, you can run the motor via an inverter on 240V. HowTo: 240V Supply to a 400V AC Motor - Application Detail explains it well.

Or you can get inverters that will step up 240 to 415V - DIGITAL 240 TO 415 INVERTERS | Drives Direct Inverters LTD

[GEOFFREY]

As a general rule I think the motors (usually older motors) wired internally were not intended to be run on 240V. Ihave been running 3ph motors on single phase for years as the 3ph machines are cheaper to buy s/hand due to lack of diy 3ph availablity.
I have also never used a proprietry inverter due to cost considerations, but have sacrificed some torque and used capacitors to give "quasi" 3ph. Whilst this may be frowned upon I have found this to be a good solution on motors up to 3HP. As Ross has decided to use a different motor this is academic, but I mention it in case someone else wants to run a 3ph motor on single phase, provided of course the motor is configured as 240v delta. G.

[Ross77]

Ok had another look tonight and the plate says 440 star, so might be in luck, bought some smaller gear pullers and got the motor apart without damaging it. Only 3 wires + earth go in to the motor there looks to be more wires joined and pushed down into the casing. not brave enough to dig them out yet, think I had better find a diagram for which wires are which coil.

if it was possible to convert to 240v what size inverter would I need? rated 0.25kW@ 440v so 0.125kW@ 240v? I have an inverter that I bought for the lathe but Its 1.5kW so might fry the small motor.

thanks for the 240>440 info but I think that if the motor cant be rewired to run on 240 then I will do the DC motor swap which looks a bit easier now I know I can use the existing top plate.
Cheers

[Ross77]

Thanks I was going to ask Geoffrey to elaborate but it think thats clear enough now. I'll have to check but I think the motor plate has a triangle on it so already delta. I've found a bit more info and it looks like the wiring is all done in the base. I'll have a proper look tomorrow.

A bit more research has also highlighted the weakness of the plastic gears so even if I can find replacements then it looks like a maintainance problem. belt drive might be worth the work.

Thanks for the info. good to know all the options

[Ross77]

Thanks Lee, good to be back. Been converting a barn for the last 3 years and still not quite finished but need some down time to try and keep me sane.

Progress will be slow but I have a lot planned for this mill, essentially it will be full cnc but with a Arduino (or similar micro processor) to monitor speed, axis DRO and act as a standalone controller for quick manual use.