eccsmk
|
| posted on 8/6/09 at 11:11 PM |
|
|
3 phase motors
is it possible in any way to run one on single phase??
ive been given a compressor and found out its 3 phase
i need it asap so if it cant be converted ill have to;
buy a new motor
buy a compressor
thanks locostbuilders
|
|
|
|
|
dinosaurjuice
|
| posted on 8/6/09 at 11:14 PM |
|
|
no
can use a converter, but they cost a LOT. edit: £250+
probably cheaper/easier to change motor or sell on and get different compressor.
[Edited on 8/6/09 by dinosaurjuice]
|
|
|
hellbent345
|
| posted on 8/6/09 at 11:16 PM |
|
|
Single to 3 phase converters (misnamed 3 phase transformers) provide three phase power from a single phase supply.
You can buy these if you google, here is a pdf from the first google site i found http://www.isomatic.co.uk/BoosterPriceList.pdf but pretty
sure you can get them a lot cheaper than that, try fleabay?
Al
EDIT but they are still going to be quite expensive, probably cheaper to change motor?
[Edited on 8/6/09 by hellbent345]
|
|
|
eccsmk
|
| posted on 8/6/09 at 11:22 PM |
|
|
maybe i should just buy a compressor
this one is a monster 250litre jobbie but i suppose a cheapo 100 litre would see me through for now
any recomendation?
|
|
|
rayward
|
| posted on 9/6/09 at 06:46 AM |
|
|
what size motor is on the compressor?, you can gaet single phase to 3 phase inverters from around £150
Ray
|
|
|
irvined
|
| posted on 9/6/09 at 07:09 AM |
|
|
What about just buying a new motor? Machinemart sell single phase motors for ~50 quid, I converted one a few years ago, it worked pretty well.
http://irvined.blogspot.com
|
|
|
hughpinder
|
| posted on 9/6/09 at 07:15 AM |
|
|
There are some fiddles you can do to run a 3 phase motor without an inverter, such as inroducing 'suitable' capacitor to produce a phase
imbalance and this does allow the motor to run. It is not very efficient, and is really only suitable for lightly loaded motors running at constant
load (e.g not stop/start and highly loaded like a compressor). I have had this dilema several times, and its always been cheaper to replace the
motor, unless you have several machines that are 3 phase, or are intending to buy several.
If its 3 phase, check the motor is not too big to run on a single phase supply (usually 3hp/2.2kw max unless you have a larger than normal supply in
your workshop e.g more than 13Amps)
Regards
Hugh
|
|
|
David Jenkins
|
| posted on 9/6/09 at 07:42 AM |
|
|
One thing you'll need to be careful about - an air compressor is about the most unkind thing that you can attach to an electric motor. They
require a lot of power just to get started, and a fair bit to run. If you don't believe me, try putting your hand (carefully!) on the motor of
a compressor that's just charged its tank from zero pressure. It will be very hot!
A 3-phase motor will have a lot of starting torque, and doesn't overheat with all the starting and stopping that you get on a compressor. A
1-phase motor has great big starting windings that may well overheat when the motor stops and starts under load.
So, the options are:
A 3-phase converter - expensive, but can be effective (note: don't get confused by all the 'cheap converter' designs you see on
Google - most are from the USA, which has a different domestic power supply). There are ways to make your own converter, but these either involve
electronics, or another 3-phase motor (pilot motor) that's started by jiggery-pokery and then maintains a reasonably good 3-phase supply. By
the time you've bought all the bits, you might as well have bought a proper converter, or a 1-phase motor.
Convert to a single-phase motor - probably the cheapest option. However, you will need to fit a higher-rated motor, for the reasons I gave earlier.
This will be physically much bigger.
Note that some compressors are kinder to motors than others: mine has a valve that dumps the compressor's output to air until the motor's
up to speed, so that it can start on minimum load.
[Edited on 9/6/09 by David Jenkins]
|
|
|
tomprescott
|
| posted on 9/6/09 at 08:41 AM |
|
|
You could also get an electrician to put a 3-phase point into your garage, currently considering the same options for some 2 post lifts. The
converters are very expensive (£250 will get you a cheap and crappy one), new single phase motors are reasonable prices probably one for you needs
will be around £150. Don't know how much it will cost to get an electrician in, but probably more than both put together.
I would guess most sensible thing or you to do would be to put a single phase motor on it, likely to cost the least and also means you can use it from
normal power sources - the converters are big and so would limit you to where you could use your compressor.
|
|
|
designer
|
| posted on 9/6/09 at 09:48 AM |
|
|
You can convert from tree to single phase by putting by jumping two of the conections with a capacitor. BUT, you loose all the power.
Try to get a single phase motor is the best option.
|
|
|
tomprescott
|
| posted on 9/6/09 at 12:28 PM |
|
|
As far as I know a three phase motor is designed so that the top of the sin waves create a steady higher voltage, I think it equates to using a
transformed and rectified single phase line. So although you could make three phase equipment work from a single phase power line, as above,
you'll get nowhere near the required power.
|
|
|
andkilde
|
| posted on 9/6/09 at 01:08 PM |
|
|
quote:
Originally posted by tomprescott
You could also get an electrician to put a 3-phase point into your garage...
Here in Canada, 3 phase power is significantly less expensive than single phase (or is perhaps vastly more efficient) a friend has a full engineering
shop, lathes, bridgeports, a half dozen CNC machines and whatnot, running fairly steadily -- his power bill is only a bit more than my household
electric bill. Downside is, it costs a lot to install the 3-phase service (thousands) and you may need to purchase some transformers as well.
If your utility will install the service for free it might make it an affordable option.
Cheers, Ted
|
|
|
David Jenkins
|
| posted on 9/6/09 at 03:07 PM |
|
|
I considered doing that - if I dug my own trench to the road, it would have worked out roughly the same cost as a phase converter.
Trouble is, the 3 phases finished on the opposite side of the road (I live in a cul-de-sac) as the supply company only need 2 phases to supply the
rest of my road.
This meant that I would have had to pay for the supply company to employ a contractor to dig a trench across the road... I didn't even bother to
ask for an estimate...
I've also heard rumours that the authorities are very reluctant to put 3-phase into a domestic property, due to the risk of connecting between
equipment on different phases (something that requires some thought to avoid in real workshop).
[Edited on 9/6/09 by David Jenkins]
|
|
|
eccsmk
|
| posted on 9/6/09 at 03:07 PM |
|
|
i have to say once again this site came up with all the answers.
im going to get a new motor
thank you to everyone for their input its helped me out once again
|
|
|
