Thread: Emco Mentor Mill conversion
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.
The Following User Says Thank You to m_c For This Useful Post:
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.
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
Last edited by Ross77; 02-04-2013 at 10:52 PM. Reason: spelling
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
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.
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.
If it is star, then the first thing you need to do is find the star point. *runs of to find image*
A quick google gave me the lower of the two images on this page - Star Delta Start Up Principles
(ignore the writing/figures, as it's explaining something you really don't need to worry about!)
as you should be able to see, the lefthand is Star configuration. What you need to do, is split the star point, then reconnect the coils in Delta (right hand image), and apply the power inputs to the delta points.
The motor will still be 0.25kw, however it will now require almost twice as much current, which should be around 1-1.2A of the top of my head. You can use a bigger inverter, however you'll need to alter the current limit settings to ensure it limits the amount of current should the motor get overloaded for any reason.
04-04-2013 #18I 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
Thanks Mc, worth a try.
sorry for the short reply, had to go out sooner than I thought. thanks for getting star - delta spec I was hoping to get the wire colours for each coil but the best I can find from emco is brown, blue, black, to the motor. looks like I'm going to have to find them buy trial and error, or testing. as a starting point Ill draw up the existing arrangement and get back back to you if that's ok?
Thanks again for your help. if there is a way to get this working on 240v then I'm keen to sort it out so I can test the machine before I make to many plans.........looks like some gorilla has been pounding on the draw bar with a hammer to release the collet holder and bent the top part of the spindle. arrgg
Stick with it it Ross. I am fairly sure you will be able to run that motor on single phase with with your inverter (or capacitors!).
When you check out the wiring you should be able to find the star point fairly easily, and once the wires are separated can then just do a simple ohms check to identify the three windings. Reconfigure as delta and you will be away. Good luck. G.
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