Lathe motor help req.

My 6'' Colchester Student made a funny smell and now the motor just hums. It's a 3 phase jobby run via one of those magic boxes that turns single to
three.
Motor is a 1420rpm Lanchashire Dynamo and Crypto of 1 1/2 hp. I took the top off it and with my AVO discovered continuity only between two of the three wires.
Two Q's:
1: Am I correct in thinking the motor is bsuggered and not worth fixing?
2: Machine Mart motors look value for money, would one be OK for this application and would a 1 HP example give my magic box an easier time? (which sometimes struggles to kick it off on a really cold morning when the oil is thick)
Cheers Julian.
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[1] Yup
[2] No First off the machine mart motors are crap. What is the output from your invertor drive is it 1-1/2 hp or what ?
Where are you located. ?
Those lathes will take some going from cold anyway, motor size isn't anything to do with it. We used to have a harrison in an unheated building and if you tried for a high speed on a cold morning it slipped the clutch and this was on true 3 phase
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wrote:

[1] Yup
[2] No First off the machine mart motors are crap. What is the output from your invertor drive is it 1-1/2 hp or what ?
Where are you located. ?
Those lathes will take some going from cold anyway, motor size isn't anything to do with it. We used to have a harrison in an unheated building and if you tried for a high speed on a cold morning it slipped the clutch and this was on true 3 phase
Thanks for the reply, I'm located near Warrington
The converter is a Transwave with 2.2Kw max output. It has a knob on it with 6 graduations that do something to the output. It works great on my Modig vertical mill with an additional pilot motor, but struggles a bit with the Colchester, in particular the solenoid contactor - tends to rattle on and off a bit during start.
What would you recommend I buy. I'd maybe be better fitting a single phase motor, but am uncertain how to retain the reverse facility.
Julian.
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<sniped a bit>

Julian, I have a Colchester Bantam with the 2-speed motor, that also runs off a transwave static phase convertor, but 3Kw/4Hp.
The Bridgeport (also 2-speed motor) runs fine on speed 1 with the phase convertor set on position 3 out of 8. Speed 2 requires setting 5 or 6.
The Bantam will start up at speed one with the convertor set at 3, BUT, if cold or with a heavy item in the chuck or a heavy cut going on, the phase convertor will start to 'stutter' as the boost contactor drops in and out, and I know then that I need to notch the setting on the convertor up a bit. When it's warm I can drop it down a notch.
Also, and I don't know if yours is the same, but you can listen to the noise of the motor and hear what boost setting it's happiest running on. Sounds strange, but quite true! If the boost level is too high the motor sounds likes its grinding a bit, notching it down cures this.
Now I'm a bit electrically dyslexic, so someone will correct me if I'm wrong, but I beleive you can get a load imbalance on the different phases from a static convertor, and sometimes changing some of the phases over (make sure it doesn't run in reverse if you do, as it can do this) will balance the load out a bit.
Peter
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wrote:

Yes I understand what you say, I've discovered that the start boost circuitry can start to ''boot-strap'' if the knob is in the wrong position. You can tell when the motor is happy, it sounds more like a Rolls Royce engine, when not it sounds like a Simca :-)
Also, mine has a mains input ammeter, I'm guessing that things are best when the ammeter reads as low as possible? (all other things being =)
Julian.
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wrote:

just hums.

single to

took the

the three

fixing?
this
time?
when
?
was
it with

Modig
with the

on and

single phase

I ran a round head Student off a Transwave static converter for years with no problems, so the set up is a good one. It may be that you have the 'wild leg' of the converter feeding the contactor coil, which would explain the chatter on start up.
AWEM
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On Sat, 17 Jan 2009 19:22:47 -0000, "Andrew Mawson"

Talking of which, how do you check which it is? Just stick a multimeter (probes I mean, not the meter itself<G>) between each phase and neutral and measure it? Also, what sort of reading (range) would you expext to get?
I need to check this on my Bantam, and also which side(phase?) the transformer for the lo-vo light and suds pump run off. I haven't had the pump on yet, but the first time I wired th lathe up the lamp glowed almost as bright as the sun, and the machine popped all the 500V fuses until I swapped the phases round a bit, so I suspect these were straight into the hot side.
Bear with me on the electrical ignorance...
I n
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wrote:

years
have
these
You're looking for equal current down each leg of the motor, so a clamp ammeter is the easiest. However measuring 'phase to phase' and tweaking the capacitor bank to get the best voltage match (ie all closest to the same value) comes a near second. Colchester suds pumps are usually three phase so I don't understand your question - the low volts light probably has a 415v primary, so should be connected across two phases.
AWEM
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wrote:

I have another question regarding my Transwave converter with its max output of 2.2Kw (from the data plate)
Say I connected it to (for argument's sake) a 10hp motor, just sat on the floor and not coupled to any load. To just spin the motor only would not really require any appreciable power input, so would my Transwave do the job?
Julian.
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Julian wrote:

You would also have to get it up to near correct speed as well before switching on. I expect you would need to add some capacitors in parallel with the internal running ones. It would be essential to make sure you don't overload the transformer so keep the input fusing correct.
Not really sure what you are hoping to achieve with such a large motor used in this way.
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wrote:

Nothing really, it was just a thought that I had, there wasn't any intention to try it out mainly because I haven't got a 10hp motor to hand! (can't get my mind to switch off sometimes :-0)
Looking at my old lathe motor, it is a really old design with internal fan and slots cooling. I bet it's given up the ghost because of damp created by the recent mild weather following the cold spell. I'm wondering if an enclosed motor would be a better bet for me because I only use the lathe on odd occasions and it spends most of it's time in a cold damp workshop with the bright bits sprayed in oil to stop rust.
Julian.
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Julian wrote:

Most motors even old ones are reasonably tolerant of changes in humidity but a modern TEFC motor will be much better if you are changing it. Do check that a new motor is not too long . Older motors tended to be short and fat compare to modern ones.
good luck
Bob
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wrote:

To everyone who replied. I've had my original motor rewired. The chaps said it was the best option because the motor is far better than any modern one, which would also have different dimensions and make mounting and fitting the belt a PITA.
I spent an hour yesterday trying to work out why the new motor wouldn't run, completely dead with no power getting to it, after much tracing of wires I discovered the microswitch cut-out that is activated by the side cover, (which I had off at the time) not my best moment :-(
Julian.
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In article

With an inverter, or some other variable speed drive, you can always try starting it at a low setting and cranking it up gradually.
David
--
David Littlewood

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I have an original, and working, motor from the same machine. 3ph and 3hp with the twin V belt pulley. Yours for beer tokens though I am near Exeter.
hth
--
Roland Craven
Nr. Exeter, Devon, UK
  Click to see the full signature.
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Thanks for the offer, I was semi-tempted but realised that my converter would probably be unable to run it. I've spoken to a mate this PM, he has recommended a mate called ACT motor rewinds in Runcorn. He will rewind or supply new, whatever is the most cost effective, so I think I'll give him a call on Monday.
If anyone has a suitable 1 1/2 HP 3 phase motor that's in good nick near Warrington I'll give you some cash for it. In an ideal world it needs a 3/4'' shaft to suit my flat belt pulley.
Julian.
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