prv
Well-Known Member
For the last ten years or so I've pretty much only worn a tie for weddings and funerals. I certainly don't wear one in my shed
Pete
Connverting 3 phase drill to single phase
- Thread starter sarabande
- Start date
For the last ten years or so I've pretty much only worn a tie for weddings and funerals. I certainly don't wear one in my shed
Pete
oldbilbo
...
haha reminds me of someone in my class as school. While dangling his tie against the chuck he started the sentence "I don't need to tuck my tie in, it's not like it'll just catch". As luck would have it he was at least smart enough to know where the big stop button was
Some schoolboys of my acquent might have been dangling other than their ties against the chuck..... Once, just once!
DownWest
Well-Known Member
I have two Meddings, one three-phase, the other single. The motors are the same size (even look the same).
sarabande
Well-Known Member
LadyInBed
Well-Known Member
I bought a single phase pillar drill from Aldi or Lidl, not very expensive and pulley and belt system to change speeds.
I've been very pleased with it.
I've been very pleased with it.
john_morris_uk
Well-Known Member
Mine looks a bit like that. But it was only a very few £ second hand...
William_H
Well-Known Member
I have to say that I have IMHO never seen such bad advice given in the guise of a serious U tube video. That is a terrible idea using a capacitor to the other 2 windings of a 3 phase motor. At best the motor might rotate but with very little power and probably a lot of overheating. Short answer buy a single phase motor or get 3 phase connected to your workshop.\ proably much more expensive.
An AC iduction motor has a winding in the frame that generates a magnetic field which induces current in the rotor which forms a magnetic field which reacts with the original field to cause rotation. Unfortunately it is a bit like pedals on a bicycle. a push down from the top can result in either no movement or movement in either direction. So on start up we need a help to get it up to speed. This is done often with another small winding fed bya capacitor to give a small phase change which is enough to encourage the whole thing to start. Often this winding is disconnected witha centrifugal switch.
A 3 phase motor has essentially 3 identical windings mounted around the frame at 120 degre spacing. This is equivalent to 3 people on a bicycle with pedals set at 120 degree spacing. So you will alwys get a positive one direction start. The 3 phases provide a lot of torque and lower current in each pahse for larger power. Hence really big motors are always 3 phase.
To try to run a 3 phase motor with one phase powered plus the other 2 phases fed by a capacitor with some variable amount of phase shift seems to me would result in very little motor power. each pahse winding will be quite high resistance (low power) becuase the motor is made to run on 3 windings powered simultaneously and then it is doubtful the otehr windings could produce much torque in themselves.
So I might be wrong but my gut feeling is that the method described in the video is really bad. I think an old washing machine motor might be a solution if a bit low powered other wise get a proper sized single phase motor or better a single phase drill press from China. good luck olewill
John the kiwi
Well-Known Member
I am an industrial process engineer and have just completed a small project that utilised two pumps that each needed a sub 1 kw motor.
(Most projects i do involve much larger motors where 1 phase is not an option at all.)
Both pumps were available with either single or three phase motors.
The installation site had 1 and 3 phase power available.
Now any industrial engineer will never use a single phase motor as they are more expensive watt for watt and being more complex are less reliable as a rule than 3 phase. It also seems that builders generally design 1 phase motors to be cheap and cheerful compared to industrial strength 3 phase motors.
(This may be a generalisation but is generally true.)
OTOH contactors and overloads for 3 phase motors cost more...Myself and my Electrical designer spent a lot of time weighing pros and cons.
End result was we used Single-to-3 phase Variable frequency drives built by WEG (who are known to build one or two electric motors!)
These not only allowed us to connect the project to a single phase supply but also to use 3 phase motors.
The Weg units replicate the functions of contactor and overload at a comparable price, and then as a bonus give us variable speed capability at the twirl of a knob!
I am well impressed with these units and looking to replace my tired old single phase Saw bench motor with a 3 phase unit.
2nd hand 3 phase industrial motors are cheap and quite available compared to single phase motors.
So Single to 3 phase converters are definitely available, reasonably priced and include variable speed capability.
Probably not available at B&Q, and best if you can find someone to buy for you at trade rates too.
Good luck.
(Most projects i do involve much larger motors where 1 phase is not an option at all.)
Both pumps were available with either single or three phase motors.
The installation site had 1 and 3 phase power available.
Now any industrial engineer will never use a single phase motor as they are more expensive watt for watt and being more complex are less reliable as a rule than 3 phase. It also seems that builders generally design 1 phase motors to be cheap and cheerful compared to industrial strength 3 phase motors.
(This may be a generalisation but is generally true.)
OTOH contactors and overloads for 3 phase motors cost more...Myself and my Electrical designer spent a lot of time weighing pros and cons.
End result was we used Single-to-3 phase Variable frequency drives built by WEG (who are known to build one or two electric motors!)
These not only allowed us to connect the project to a single phase supply but also to use 3 phase motors.
The Weg units replicate the functions of contactor and overload at a comparable price, and then as a bonus give us variable speed capability at the twirl of a knob!
I am well impressed with these units and looking to replace my tired old single phase Saw bench motor with a 3 phase unit.
2nd hand 3 phase industrial motors are cheap and quite available compared to single phase motors.
So Single to 3 phase converters are definitely available, reasonably priced and include variable speed capability.
Probably not available at B&Q, and best if you can find someone to buy for you at trade rates too.
Good luck.
AntarcticPilot
Well-Known Member
This chimes with what I recall from my boyhood experience of making a linear motor - it is a LOT more complex getting the phase shifting correct than this video suggests, and while you might get something working, for a rather restricted meaning of "working", it certainly won't work with full efficiency. William's concerns about burning out the motor also ring true.
Jean
Well-Known Member
More to consider of course if converting single to 3 phase, including how the existing motor windings are currently connected for rated torque and power (star or delta). If currently star, then could use a simple 230v 3 phase output, with motor reconnected in delta (if winding connections are accessible), else need a more sophisticated 420v 3 phase output unit, as per examples here perhaps (but I've not read their spec so can't be certain): Another problem too perhaps is existing motor suitably inverter rated (voltage spikes, for example, can damage insulation if not). http://www.motorsandinverters.co.uk/Phase-Converters/STC-Static-Converetr-Hi-Torque-c119/
DownWest
Well-Known Member
Almost any pillar drill is better than a hand drill ,even if it is in a stand. Mainly because of the low constant speeds and the controllable pressure.
One of my Meddings has a very 'well drilled' lower plate, bit like the pic above, but worse... My father bought it in June 1960 for the trailer works (Meddings told me that) And it got well abused. Still going strong.
andygc
Well-Known Member
Might I just point out to the nay-sayers that the completely bog-standard way of converting a woodturning lathe from fixed speed to variable speed is to chuck out the single phase motor and replace it with a three phase motor controlled by a single to three phase convertor. New variable speed lathes that don't use cheap and cheerful variable diameter pulleys also have three phase motors. The final product has bags of torque (and a top speed that's just scary). If would work just as well for a pillar drill, with the bonus of not having to shift the belt every time you want to change the speed.
John the kiwi
Well-Known Member
You are correct on all counts of course and we could only use the single to 3 phase convertors because all the winding terminations were accessible.
The motors were inverter rated. NZ also uses IEC standards and there is a requirement to use correctly shielded Cable between the Inverter and the Motor.
Nonetheless this was still a good simple option for someone with the right knowledge. I guess i should have advised anyone doing anything like this to get the help of a good experienced industrial electrician. (Note electricians are not all created equal and some electricians that spend their days simply wiring new houses and offices are almost dangerously ignorant about motors and inverters and other stuff. (As always its horses for courses.)
Please do remember that 240 volts can kill you.....Get a professional to help.
Cheers
Boo2
Well-Known Member
There's some interesting info on running 3 phase motors from a single phase supply here : http://www.lathes.co.uk/page27.html
If you are rich then Newton Tesla sell complete motor-inverter-controller packages here http://www.newton-tesla.co.uk/index.php?route=product/category&path=74_143 but you would only really need an inverter available here http://www.newton-tesla.co.uk/index.php?route=product/category&path=74_195 and here : http://www.drivesdirect.co.uk/
Hth,
Boo2
