Two Speed Reverse Single Winding Motor

Nick Hacking said:
............It dawns on me, however, that if I'm going to trust the tramming device, it has to be properly square, and so............Nick
Click to expand...
You don't have to be concerned with having the tramming tool perfectly square. Just zero the indicators at the same spot on your vise or table. In order to hit the same spot, they will have to be the same distance out from the spindle axis though.
 
A quick update, in case anyone is really interested.

The low-voltage control circuits that I improvised and the conversion of the anglepoise lamp to use a 12V LED have now been running without any issues for more than six months.

The motor continues to run well at 240V from the VFD although its sometimes "sticks" on start up. I don't think that the alterations to the case geometry that I caused by slitting the case open have done the motor any favours: I should really pop the top cap off the motor housing and look at the bearing again. I may end up having to put a substitute motor in, one day, but this is going to involve grafting the end of the long shaft onto the new motor. Someone has posted a thread about doing this (with success) but for now, I'm happy to simply feed the machine a new bearing race every few months.

The X-feed stalled a while back, immediately melting the Chinese 240-120V autotransformer, so that's now in the scrap bin and I'm using a big, external transformer rated at about 1KW. It's over-kill, but it was cheap, it works, and with the transformer sitting on the floor behind the mill, it's hard to notice the difference.

All in all, the conversion from 415/480V 3-phase to 240V single phase has been a success. The machine can fairly rip through metal with the right cutter, I'm now definitely the weak link in my home manufacturing set up.

Kind wishes,

Nick
 
Good deal Nick, reading this thread with interest. Glad you got it sorted
Mark S.
 
Thanks, Mark but all is now woe, death and destruction.

I was out in the workshop this afternoon, hiding from the family (in the UK we have a holiday period between Christmas and New Year when many people take time off) and milling away like a demon, all pleased with my powerful Bridgeport and my fancy powered X-axis. I was making a toolpost for my old Sheldon lathe, as it happens... anyway, all of a sudden, the mill stopped and the VFD said "E GF" which I took to mean "error: ground fault" so I lifted off the motor and stripped it down, fully expecting to find that with the heat my insulation tape had softened, allowing the sharp edge of one of my solder joints to contact the case.

Sadly, even with all of my connexions pulled well free of anything, there is now a low resistance between one of the coils and the case. I think the poor old thing is toast.

Firstly, I'm going to see if I can find a 3-phase motor with a shaft of 3/4" diameter and 4" stick-out. If that draws a blank, things may get more complicated. Blast: just when things were going well and I'd started to get a feel for the machine. C'est la vie.

Kind wishes,

Nick
 
Sorry to hear that, sometimes old motors' windings insulation breaks down when subjected to the spiky waveforms that VFDs generate, hence the
modern term "inverter rated" motor
Mark
 
Thanks again, Mark. That might explain it.
At least I got a few months use out of the motor, and leaned a good deal about wiring 3-phase motors, thanks to the good folk here.

Kind wishes,

Nick
 
Your experience got me thinking that line filter chokes in each of the three legs between the VFD and the motor might be a good idea for
older motors- they would have to be high current chokes >10 amp but I don't know how much inductance would be required.
Mark
 
markba633csi said:
Your experience got me thinking that line filter chokes in each of the three legs between the VFD and the motor might be a good idea for
older motors- they would have to be high current chokes >10 amp but I don't know how much inductance would be required.
Mark
Click to expand...

Maybe we should ask Henry?
(Sorry: too many Christmas cracker jokes recently)

Nick
 
HO HO HO! :cupcake: (or maybe we should ask his dwarf helper Micro-Henry) HAR HAR
 
Yes, sorry about that.
Now that I'm back at work and stone-cold sober, I can hardly believe that I thought it was funny.
So, we shall not mention his niece: Millicent.

[fx: tumbleweed]

I found a replacement Bridgeport motor on Amazon! Hurrah! Sadly £1,300 including import duty and delivery. That's about $1,750 US and since I only paid £2,000 for the whole mill, it seems a bit steep. Fortunately, I've found a three-phase motor from a UK company which is "VFD rated" at only £150, delivered. I'll have to hack the spindle about and do some work on the mounting - but that shouldn't be beyond me. I don't think that I even need to bother mounting the whole 4-step pulley stack: I never shifted the belt once when the motor was working, I used my VFD to vary the speed.

God-willing, the motor should be here in a few days and when I get around to fitting it, I'll post an update.

Happy New Year.

Nick
 
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