Thread: Arboga EM825 mill Christmas present

Originally Posted by RayG

Hi Ken, Eskimo, Greg,

I think running the motor as 4 pole 50hz=1440 rpm, 100Hz=2880 would give better torque and versatility in the 1440 and lower range than running as 2 pole 50Hz=2880, 25Hz=1440.


I talked with my son-in-law who is a motor rewinder (4th year apprentice) and he tells me it's usually just a 10 minute job to find the star point and bring out the extra wires to convert to delta. Nothing needs to be rewound. You could get them to remove the extra wires for the 2 pole switching to make it easier to wire up. Any good motor rewinder should be able to do it at a reasonable price.

Regards
Ray

PS: Have you considered a basic el-cheapo home-brewed RPC? I'm thinking just a 2hp idler and a single phase kick starter...

Ray, that's my point exactly. Powering the 4 pole windings frees you from having to buy a more expensive sensorless vector VFD for constant torque as the simple V/Hz type still provides maximum torque (and current) at higher rpm. The torque does fall off with speeds above 1440, but the horsepower remains constant.

Very interesting information regarding the star point. Very interesting indeed.

Finally, an RPC would work for this motor, but only if there was either:
a) a step-up transformer installed to use the motor as is, or
b) the star point for both windings could be brought out so that it becomes a two speed 240v/3~ motor. I don't know? Is that even possible?


I had a five hp RPC for a couple of years. I'm glad I don't have to listen to the growl of that motor anymore. (but I would make another if I am ever again without native 3~ power.)

Greg

RayG,

Have sent you a PM. I'm not keen on using an RPC, they are noisy and cumbersome. Prefer something more hi-tech.

So far have drawn a blank on a 240V to 415V VFD from somewhere local. Can source one from England, but they are expensive, and will attract a hefty freight charge.

Looks like I will have to try and remove the motor stator, and get a Y point fished out. According to another forum, 3 screws hold the stator inside the head casting.

Greg,

All your comments make sense. I agree, delete the 2 speed switch and retain the low speed setting.

I hope we are all learning from this discussion, there must be other members with the same problem!

Fun and games!

Ken

Ken, my drill has the same configuration, and I can confirm that the stator is retained with four set screws.

Greg

Thanks Greg,

Shouldn't you be working out in the shed on your Deckel, we are all waiting for some snaps.

Ken

If any Arboga owners are listening, drill or mill/drill, have you pulled out your stator winding?

This I need to do, is it easy or otherwise?

Ken

Hi when I got my mill it was in boxs in bits.
ok, you may to pull it all a part.
can not recall how armature shaft gos into the gearbox if it will slide out.

1
You can try by pulling motor end plate off ( fan end ).
to get the armature out first.
to get the stator winding there are 2 gurb screws about 2 in up on the motor housing.
Left side . if it will not come lose may be more at back of head.
You may get the winding loose, but to get it out is hard as for the 6 wires running
down to the switch.

2
pull the lot apart.

Tony

Ken,
You will then need to make up something to push on the rim of the stator laminations to push the stack out and in again after rewiring. I rolled up a sheet steel cylinder which was thin enough to go between the windings and the inside of the casting. A metal disk was used to push on the cylinder to apply the necessary force. In my case it did require a press to get the parts to move.
When putting the stator back in it is difficult to get the grub screws to line up exactly, I suspect that it is not that important so long as the relationship to the end of the casting is as it was when removed.
I have some photocopies of the (brief) factory instructions for the removal of the stator, PM me if you would like a copy. Regards, Mm.

Hi MM.

PM sent. Would greatly appreciate copies of the stator removal. Is it a big job?

I presume the only way out is down after the fan cover is removed along with the stator fixing screws.

Ken

Bit late to join this thread but I have had one of these for about 25+ years, same as yours mine was a 3 ph 2 speed job. I initially mounted a pulley on the bottom of the motor shaft and hung a 1/3hp 1ph 2 speed washing machine motor out the side and connected a v belt to drive it. Worked fine used it for about 2 yrs like that. I then came across a motor rewinder who claimed that he could rewind the motor to operate on single phase. The job was done ( I recall that I took only the motor part of the castings to him) I had to rig up a start switch as 1 ph motors need the start winding to be energised, the start switch is a micro switch mounted on the original on/off panel in such a way the fully depressing the start switch activates the microswitch and energises the start windings, on releasing the start switch it latches on but comes out just enough to release the micro switch and disconnect the start winding. To start it I press the start switch in all the way hold it for a second or two and then let it go, been doing that for about 20 yrs.
I can't recall the exact speeds of the two windings but I think that the motor winder said they are same as the original.
How good is the rewind job ? high speed is just fine plenty of power and is usually used only on small diam. cutters anyway. Low speed does lack power and it here that you need it for larger diam cutters I'm guessing that it is less than 1/4 hp, however knowing its limitations it can do good work, in fact I made a quick change tool post for my lathe, most of it on the mill. I milled 12 tool holders, the main body of the tool post and the locking cam (made of stainless) with no problem using home made t slot cutters and commercial end mills.

I plan one day to investigate the possibility of pressing the motor windings out and mounting a 2hp dc motor inside the motor casting I have one scrounged from a motorised treadmill complete with speed controller. I had contemplated selling it at one stage and buying one of the belt operated Taiwan mill drills but after using one for a month or so I though no way, the Arboga is a much better machine, and mine came with a Clarkson chuck and collets.

I don't recall the motor rewinder's name, I only recall that it wasn't that far from my wife's (girl friend at that time ) parents at Northfield SA. Good luck with your machine it is worth the trouble.

watching this thread leads me to believe that you have only 2 options..
buy the single phase to 3 phase VFD/VSD
or
get 3ph installed to the premises

the 1st option is the cheapest, but is restrictive...only in the terms of not being able to get more 3phase machines in the future

trying to get a replacement motor cant happen...most likely nothing is available
or to
retrofit a another motor externally is impracticable...the cost (and your labour time) will most likely exceed the cost of a VFD/VSD

time to bite the bullet Ken! ...

dont sell it...its probably much much much better than my CW7750 err aka HM52

Originally Posted by eskimo

watching this thread leads me to believe that you have only 2 options..buy the single phase to 3 phase VFD/VSD or get 3ph installed to the premises

What's your reasoning for not including the rotary phase converter solution?

Jordan

Originally Posted by nadroj

What's your reasoning for not including the rotary phase converter solution?

Jordan

cost...foot print (size)

Originally Posted by eskimo

cost...foot print (size)

But you include far more costly 3 phase mains power?
True enough about the size though - another box to find a home for.

Jordan

Originally Posted by nadroj

But you include far more costly 3 phase mains power?

i hav'nt seen any prices as yet

but I would guess it would be more expensive than a rotary phase converter...but its permanent and shouldnt break down.....