Which Motor for my mill?

[Oldmanandhistoy]

Hi all,

I'm looking for your help to select a motor for my mill, it's an old Harrison http://www.lathes.co.uk/harrisonmiller/index.html I will be using the vertical head.

What I want to do to start is run the machine as is for now but I only have a 240Vac 13amp supply. In the future I want to add variable/computer controlled speed adjustment and more power at a bit higher rpm.

So I thought the easiest way to start would be to replace the 415v motor with a single phase 240v one. Like this one http://cgi.ebay.co.uk/Electric-Motor...1%7C240%3A1318 or this one http://cgi.ebay.co.uk/Electric-Motor...4.c0.m14.l1262 but while searching for motors I've noticed there are variables which course me confusion like:

1400rpm or 2800rpm

Capacitors

3 phase or single phase

Numerous phase inverters/converters

So what do I do, single phase motor 2800rpm (saves me changing the pulley to give me the higher speed range); 2hp or 3hp (more power for a higher top rpm)? Or would this be the wrong route to add variable speed latter?

So what's the right way to do this?

All/any help is very much appreciated as always.

John

[Kipper]

A dilemma mate! I had similar choices a while back and replaced the 1ph 1.5HP 1400RPM motor with a 3HP 2800RPM unit and a 3KW phase inverter £130 for the motor and £179 for the phase converter (Drives Direct in Nottingham) Would I go for fixed speed ever again? not on your nelly! The phase inverter runs to 200HZ+ which would no doubt destroy the machine Simple to install and for 8mths it's been 100% reliable.

[Oldmanandhistoy]

Hi Kipper,

I've been looking at their listings on Ebay and considered contacting them for info but worried about them giving me the best advice over making a sale so thought I would ask here first.

Is your drive controllable via Mach3 for variable speed or am I missing something?

John

[Kipper]

Originally Posted by Oldmanandhistoy Hi Kipper, I've been looking at their listings on Ebay and considered contacting them for info but worried about them giving me the best advice over making a sale so thought I would ask here first. Is your drive controllable via Mach3 for variable speed or am I missing something? John

It can be controlled from Mach (via a motor drive board which converts pulse to voltage 0-10V) but I run the machine at the same speed all the time...5000RPM The drive is programmable for ramping up/braking and way too many things Give em a ring...nice people!

[fatal-exception]

Yep, go 3 phase if you can. Variable frequency drives can usually take a 0-10VDC input for speed control. As long as your breakoutboard has 0-10VDC out, your laughing.

Paul

[Oldmanandhistoy]

Originally Posted by Kipper Would I go for fixed speed ever again? not on your nelly!

Originally Posted by Kipper but I run the machine at the same speed all the time...5000RPM

LOL

I understand where your coming from there as I will probably be mostly using the top speed only for Aluminium work and why I could cope without variable speed for now.

John

[Oldmanandhistoy]

Originally Posted by fatal-exception Yep, go 3 phase if you can. Variable frequency drives can usually take a 0-10VDC input for speed control. As long as your breakoutboard has 0-10VDC out, your laughing. Paul

So 3 phase is better than a single phase motor? Could you tell me why or link me to more info?

John

[fatal-exception]

Inverters for single phase motors are not common, expensive, and complicated, that's why I would go 3 phase if you plan on controlling it from Mach3. VFD's for 3 phase motors are commonly used in industry, and built to last, as are the motors.

I believe that 3 phase motors are also more efficient than single phase.

Paul

[Oldmanandhistoy]

Originally Posted by fatal-exception Inverters for single phase motors are not common, expensive, and complicated, that's why I would go 3 phase if you plan on controlling it from Mach3. VFD's for 3 phase motors are commonly used in industry, and built to last, as are the motors. I believe that 3 phase motors are also more efficient than single phase. Paul

Thanks for the info, very helpful.

John

[Kipper]

Originally Posted by fatal-exception Inverters for single phase motors are not common, expensive, and complicated, that's why I would go 3 phase if you plan on controlling it from Mach3. VFD's for 3 phase motors are commonly used in industry, and built to last, as are the motors. I believe that 3 phase motors are also more efficient than single phase. Paul

You missed out the most important aspect of 3ph motors for a Yorkshireman........They're cheaper

[Al_The_Man]

Originally Posted by Oldmanandhistoy but while searching for motors I've noticed there are variables which course me confusion like: 1400rpm or 2800rpm Capacitors 3 phase or single phase Numerous phase inverters/converters So what's the right way to do this? John

1400-2800 is the rpm you get for either a 4 pole motor or 2 pole motor on 50hz.
Capacitors are used on 1 phase motors to set them into rotation in the correct direction.
1 phase motors on a variable frequency drive will drop out of run quite easily if under load at low rpm.
It hasn't been mentioned that you can get 3 phase out with 1 phase 240v in on a VFD.
I would go with a 4 pole motor, this allows doubling the Hz up to around 120Hz for both UK and N.A. This effectively doubles the base speed of the motor.
Al.

[Oldmanandhistoy]

Originally Posted by Al_The_Man I would go with a 4 pole motor, this allows doubling the Hz up to around 120Hz for both UK and N.A. This effectively doubles the base speed of the motor. Al.

Thanks Al,

So why not go with a 2 pole motor which is double the speed in the first place?

Does anyone have a good link to an informative website about electric motors; I need more basic understanding I think ?

John