ned
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| posted on 25/6/06 at 09:23 AM |
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converting 3 phase (again)
Having got the drill etc as per my other thread I'm looking at the options to convert it. I guess I have a few questions about this...
1.) As I see it there are a couple of options:
fit a replacement single phase motor:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=019&item=290000406311&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1
replacing the motor would/should be a simple swap and all gearing etc would remain the same though the motor might have less torque?
or fit a converter/inverter type box thingy:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=006&item=160000744629&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1
the converter/inverter route seems better as I could reverse the motor and have variable speed control via the panel or by fitting a potentiometer.
2.)I have read up on the web about 3 phase power but still don't fully understand it, I know it provides 3 phases at 50hz but I don't
understand why some places say you can have 220/240volts 3 phase - I thought the whole point of three phase was that is was 380-415volts?
3.)If I were to replace the motor does it have to be identical in spec to the original one? ie could i fit a higher powered motor or would/could this
damage the machine by being too powerful (just thinking of availability of second hand motors really)
4.) I spotted this motor on ebay, though it is the right rpm but a higher power, but it says:
"This item requires a direct on line starter which does not come with the motor "
what does this mean?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7631246176&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1
thanks,
Ned.
beware, I've got yellow skin
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Wadders
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| posted on 25/6/06 at 09:40 AM |
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Hi Ned
i built a rotary phase converter which runs my lathe and drill, but inverters are so cheap and convenient now, that i would deffo go down that route.
Cheaper to run as well.
As you say 3 phase is just 3 lots of 220/240v with each leg at 220/240 50hz. so really you have 660v. 380/415 is the RMS voltage (root mean squared of
660) dont know why its quoted this way, but it is.
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cossey
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| posted on 25/6/06 at 10:36 AM |
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it is 220-240v between the phases and neutral and 380-415v between the phases. the first case you have 4 wires the second you only have 3.
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wheelfelloff
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| posted on 25/6/06 at 11:06 AM |
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Ned
Have a look at this group (http://groups.google.com/group/uk.rec.models.engineering?lnk=lr) and search on VFD, or 3 phase etc and you will get a lot
of reading on converting 3 phase machinery to single phase.
You have a number of options:
1) Run your 3 phase motor from single phase using a capacitor to produce the third phase, live and neutral gives you the first two. This will run the
motor but will be at reduced power and if you don't get the right capacitor the motor will run fairly warm. Not a problem if you are just using
smallish drills.
2) Buy a VFD, (inverter) these are solid state reasonably cheap (£100 new) nowadays and give you both full power and variable speed. You need to check
if your motor is suitable for this system - look for star/delt wired motors and it will explain.
3) You can use a converter (solid state or rotary) which will produce 3 phase but does not give you variable speed. A rotary converter is a single
phase motor driving a 3 phase motor which produces the 3 phase. They can be a bit noisey and take up room if you are limited and can be pricey to buy
as well.
4) Change to single phase, these motors are not as smooth as 3 phase are larger power for power. The size of motor you need depends on the size drills
you want to use. Most hobby drills come with 1/2 or 3/4hp motors. A standard 1400 rpm 1hp power motor will certainly not damage your machine but is
overkill for a drill unless you are going to use 1" drills.
Sorry I can't be more techinical but I'm a mechanical engineer and electrics is alien to me. I have though converted some 3 phase lathes
etc using VFD and it is fairly simple.
Hope this helps a bit
regards
Keith
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daviep
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| posted on 25/6/06 at 11:38 AM |
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Three phase describes the type of generator not a particular voltage. 415 - 440 volts is common throughout the world , however in the U.S. 240v three
phase is also quite common. 440v 3 phase is 440v between phases and 240v between any phase and neutral.
Most home built rotary convertors using an idle motor and capacitors will only produce 3 phase at the supply voltage e.g. 240v 3 phase if in the UK.
This isn't always a problem as many motors can be configured 240v "delta" and will work fine it is just something to be aware of.
It is possible to transform the supply voltage up to 440v (still single phase) and then convert it to 3 phase.
Much simpler to replace a motor IMHO especially on something such as a pillar drill where motor is fairly easy to access.
A direct on line (DOL) starter is just a contactor (switch) capable of switching full motor current, they usually incorporate overload protection
as well. Should be round about £30.
Best of luck Dave
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ned
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| posted on 25/6/06 at 11:59 AM |
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still a bit unsure what to do but thanks for the help so far. here's a pic of the motor rating plate:
http://www.locostbuilders.co.uk/upload/IMG_2172b.jpg
It is only a 0.33hp machine but if i was to get a converter which seems preferable as for near enough the same money you get a reverse and variable
speed do i need it to suit 240 or 400volt 3 phase? the motor has different ratings for both voltages and there are 4 wires coming from the on/off
switch that the motor is looped through - 3 brown and one yellow/green (earth i assume).
cheers,
Ned.
beware, I've got yellow skin
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daviep
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| posted on 25/6/06 at 01:34 PM |
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The motor in the picture will run on either 240v or 440v depending on the configuration. Normally when you open up the terminal box where the supply
connects to, on the undersise of the lid there will be a diagram showing how to connect the motor for "star" or "delta"
operation. Going by the plate the motor will run 440v in "star" or 240 in "delta".
Normally it is just a case of moving 2 small links inside the terminal box to change from star to delta. Most of the cheaper phase convertors such
asthis only give you 3 phase at the supply voltage (240v) so you would need to connect the motor up in the
"delta" configuration. Hope this makes sense.
Incidentally you are correct your 3 brown wires are the 3 phases and the yellow/green is earth. Hope this helps!
Dave P.S why are my hyperlinks not working?
[Edited on 25/6/06 by daviep]
[Edited on 25/6/06 by daviep]
[Edited on 25/6/06 by daviep]
[Edited on 25/6/06 by daviep]
[Edited on 25/6/06 by daviep]
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ned
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| posted on 25/6/06 at 07:44 PM |
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I have now removed the motor, taken off the back plate and have found the wiring diagram and the motor wiring posts. trouble is I'm not sure
that I understand the diagram as the colours seem to be different and my three power feeds going in are all brown - what am I missing this time?!!
http://www.locostbuilders.co.uk/upload/IMG_2182b.jpg
http://www.locostbuilders.co.uk/upload/IMG_2176b.jpg
any further help appreciated.
very nearly there now!
Ned.
beware, I've got yellow skin
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PaulBuz
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| posted on 25/6/06 at 08:14 PM |
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Ned
That motor has been rewound at some point.
Assuming that it was being run on a 3 phase 415V supply, it means that the motor has been 'star'ed internally.
Simply put , you can't run that motor from a single phase inverter
ATB
Paul
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ned
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| posted on 25/6/06 at 09:05 PM |
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Paul,
How can you tell that? why can i not change the wiring to.from the posts to change to a delta config? the wires internally must come from the motors 4
posts still surely?
Ned.
beware, I've got yellow skin
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PaulBuz
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| posted on 25/6/06 at 09:16 PM |
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Ned, trust me I do this for a living
'Normally a 3 phase motor will have 6 terminals.
These comprise of 3 sets of windings,with 2 connections to each winding(ie. one each end!)
To get either a star or delta connection,as mentioned above, links are fitted to give one or the other.
Sometimes, when a motor is rewound , rewinder may ask you how the motor is configured(ie. star or delta)
He then does the linking I just mentioned, INSIDE the motor .
This saves them having to bring out unnecessary ends to the term block.
If you look at your motor, you only have 3 brown wires,& since I'm guessing that the m/c was previously used in industry, the odds are it is
wired for star. 415Volts
ATB
Paul
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ned
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| posted on 25/6/06 at 09:30 PM |
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but the wiring plate diagram only shows 3 connections + neutral and that looks pretty original to me?
if it can't be used does the motor have any inherent value left ie is it worth putting on ebay to offset the cost of a new one?
Ned.
[Edited on 25/6/06 by ned]
beware, I've got yellow skin
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PaulBuz
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| posted on 25/6/06 at 09:34 PM |
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Its not as simple as that I,m afraid. the star point may well be embedded in the windings.
I don't think that the motor will fetch anything on ebay...but theres no harm in trying!
Damn! you edited it!!
Still no good
Ned
I've just had another look at the photo.
The star point IS in the term. housing.
If you undo the term. marked 'N', is ther 3 wires going to it?
[Edited on 25/6/06 by PaulBuz]
[Edited on 25/6/06 by PaulBuz]
ATB
Paul
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ned
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| posted on 25/6/06 at 09:38 PM |
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oh well, at least i don't have to refit it then, just unwire the switch!
does this look like a good replacement?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=019&item=290000406311&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1
your help is most appreciated.
cheers,
Ned.
beware, I've got yellow skin
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PaulBuz
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| posted on 25/6/06 at 09:39 PM |
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Ned see 2nd edit above
ATB
Paul
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ned
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| posted on 25/6/06 at 09:42 PM |
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erm i've shut the garage up now but there is at least two going to the neutral, a black and a white.
Ned.
a b and c have the same colours as the star diagram, ie red yellow and blue and each with a brown power feed fom the switch going to them and the
neutral has black and white looking at the other pics i have off my digicam...
[Edited on 25/6/06 by ned]
beware, I've got yellow skin
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PaulBuz
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| posted on 25/6/06 at 09:45 PM |
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Okay
Have a look when you can, if you do have 3 wires there, you can get it running for a couple of quid with caps.
ATB
Paul
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ned
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| posted on 25/6/06 at 09:49 PM |
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edited above post and another pic
 
Rescued attachment IMG_2184b.jpg
beware, I've got yellow skin
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PaulBuz
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| posted on 25/6/06 at 09:50 PM |
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Just 2 wires don't make electrical sense.
Looking at the photo the white wire looks very thick.
I'm guessing that is sleeving over more than 1 wire. (very common practice in motor rewinds)
Have a look tomorrow & let me know.
ATB
Paul
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ned
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| posted on 25/6/06 at 09:51 PM |
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ok thanks again paul.
Andrew.
beware, I've got yellow skin
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splitrivet
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| posted on 26/6/06 at 08:52 AM |
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Just go for a single phase motor Ned its the cheapest easiest and safest option.
Cheers,
Bob
I used to be a Werewolf but I'm alright nowwoooooooooooooo
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Confused but excited.
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| posted on 26/6/06 at 03:49 PM |
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quote:
Originally posted by splitrivet
Just go for a single phase motor Ned its the cheapest easiest and safest option.
Cheers,
Bob
Don't listen to him Ned.
This is better than a soap.
Will Ned need a new motor?
What's in the white sleeve?
Will Paulbuz sort it in time?
Will Ned be asked to STAR in DELTA Force II? 
The suspense is killing me!
Tune in for the next thrilling installment, same forum, same thread!
Tell them about the bent treacle edges!
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stevebubs
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| posted on 26/6/06 at 05:47 PM |
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easiest way of understanding 3 phase is to draw a sine wave on a piece of paper that maxes out at 240
Then draw another that is 120 degrees out of phase
The draw another 120 degress out of phase with the pair.
Maximum pd / voltage between 2 points is the max difference between any 2 of the lines.....
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tks
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| posted on 27/6/06 at 09:55 AM |
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yeah
very easy right to make a good sinus wave... 
3phase 240 is the old industrial voltage.
4phase = 400volts 3phases and Neutral...
the engine need to be wired correcly to each winding because the voltage is almost doubled sow should the resistance also be to survive...
cant Ned just measure up the resistance between all the terminals?
then we proberly know how the windings are wired and if the motor isn“t shorted..etc..
we also know the amps sow should be easy to work out right??
Tks
there is a way that if you have 6 terminals that with a cap you can wire it for 230volts (single phase)
the cap than generates the 2nd phase movement... but it isn“t the ideal solution..
The above comments are always meant to be from the above persons perspective.
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BKLOCO
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| posted on 27/6/06 at 03:06 PM |
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Ned If I were you I wouldn't p1ss about with this motor.
get hold of a 1/3 or 1/2 hp capacitor start single phase 240v motor either from fleaBay or a boot sale. I've picked them up for a fiver
before.
It's the safest easiest option.
I too am a spark and the convertor/invertor route is NOT something you want to get into unless you really have to.
[Edited on 27-6-06 by BKLOCO]
Experience is what you get when you don't get what you want!!! 
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