shaper motor

Hi all well after a long time searching I have found a old shaper that needs some tlc and is heading for my shed. Its a alba 4s I think. Its got a 14 inch stroke, looks rough but a tidy up and coat of paint will sort that out. Now the thing is it's three phase, I want to change it to 240v single phase. what size hp motor would I need for it? also does anyone have any info on these machines, lathes.co.uk only has the 1a alba nothing about the 4s. thanks mark.

I put a 4hp motor on my 18" shaper, although I stayed with three phase - Andrew

The simple answer is 'same HP and rpm as as the 3 phase one it comes with'.

Consider also using an inverter on the existing motor, particularly if installing a metric motor is awkward. If you're unsure about finding the star point, a good rewinder can and also clean and revarnish windings etc.

Thanks for the help, I think it has a 3 hp motor on it but would need a power hose and spade to get through all the crud stuck on it to see it. Will see on Monday when it arrives.

Mark,

Anything over one horsepower may be troublesome on single phase, because of the surge current when it starts.

If the 3 phase motor is useable [or repairable] then, as jonathan says; an Inverter would be your best buy.

... 3 phase is much smoother, and gives everything an easier ride.

MichaelG.

You could run it on an RPC which should be cheaper to make than the cost of a 3HP Inverter, that said the inverter will give variable speed and a lovely smooth finish.

As a comparison my Alba 1a has a 1/2hp 3Phase motor and can produce a really smooth finish.

My Elliott 10m has a 3/4hp single phase and will not produce the same quality finish no matter how much I tweak the setup/tooling/lubricant.

Similar behaviour from both my single phase Boxford 8" and 7" Atlas.

Regards

Paul

Smaller motor, smaller depth of cut. with the 3 or 4hp motor, it will remove a large amount of material in a short time, big hot chips all over the place! Ian S C

Humm I think i'm starting to lean more towards the inverter side if the motor can take it. A nice smooth finish is what i'm after and I can get the inverters and a motor if needed cheapish at my workplace. Can anyone explain why a 3 phase motor is smoother running than a single?

.

Mark,

In the simplest possible terms ... because you are using three times as many pulses per rev.

It's just like the difference between a single cylinder motorcycle engine and a nice 120° triple.

MichaelG.

It's a little bit more subtle than just the number of pulses.

If we take a single phase motor, with a single pair of poles, the resulting magnetic field just pulsates at the applied frequency, there is no rotation of the field. That's why single phase induction motors need extra gubbins (windings, capacitors etc) to create a rotating magnetic field to the get the motor started. Even when running the single phase motor has inherent pulsing.

If we now consider a three phase motor, with three sets of poles spaced 120° apart, and fed by three phases 120° apart we get three pulsating magnetic fields, one across each set of poles and 120° apart. However, if we look at the resultant magnetic field from all three pairs of poles, the field rotates at the same rate as the frequency of the applied voltages. That's why a three phase induction motor is self-starting. Another important result is that the magnitude of the rotating field is constant, so there is no pulsating.

That's why a three phase induction motor runs more smoothly than a single phase one; it's inherent in the way that the motors operate.

Regards,

Andrew

Ah I see, well that has clinched it for me, the inverter it is. I'll put up some pics when she arrives. thanks all

No argument with your extended explanation, Andrew.

MichaelG.

Yea my baby has arrived, dam its a star only motor oh well, still its only 2 hp. Time for more shopping. Got it of the trailer and in the shed time for some cleaning. Can any one tell from the serial what year it is? also its a alba 2s not a 4s. Its actually not that bad under all the crud. Anyway some pics for yens.

Edited By mark mc on 15/11/2013 14:15:02

Looks very useful, Mark !!

MichaelG.

Great find your machine looks complete.

Star only motors very often have the star point in the outer layer of one end of the windings this requires the ties cut from the windings pick out the star point separate the wires extend/add some tails and you now have six wires coming out of the motor (Delta).

If you feel adventurous there are a some good books in the Workshop Practice series written by Jim Cox & Graham Asterbury which describe how this is done.

I have done many with great success.

Here you can see the 3 original wires coming from the windings at the back of the pic and at the front the freshly exposed Star Point with the three wires now separated

You could probably find a motor repair shop to do it for you but if you like a challenge.....

Paul

That's a interesting idea you have there Paul might be worth a shot. I'll get the motor off and have a look see and order the books, thanks.