Union Graduate, worth switching from 1 to 3 phase motor?

[Rowan]

Hello,

I'm trying to decide between replacing the motor on a Harrison Union Graduate Lathe with another 1 phase motor, or if it is worth doing the more expensive option of a kit containing a 3 phase motor, inverter and replacement control panel.

I think there are a number of advantages to to the 3 phase option and I need to stop/start the lathe very often, so I think this might be more suited to 3 phase?

I'm interested to know if people have done this, do they think it was worth spending the extra?
I'm particularly interested in whether anyone has noticed much of a decrease in chattering when switching to 3 phase motor?

Many thanks,
Rowan

 

[stewart]

No experience of doing this to a graduate but I loved it when I fitted such a kit to my record cl2 lathe. Electronic speed control is great! If you can afford it, I say go for it!

 

[flh801978]

Absolutely well worth doing
I have 2 graduates both with upsized motors and vfd’s On them
Also reverse is well worth having

Ian

 

[deema]

It depends on what your turning I believe. I did it one of my lathes and didn’t actual use the variable speed so sold it! I still have a single phase fixed speed motor Graduate. I converted it myself rather than buying a kit. I preferred to have a power on off switch on the panel that is illuminated so I didn’t leave the lathe powered up when I finished for the day!

You can get single phase inverters that means you don’t need to swap the motor. The motors have an imperial shaft which makes them expensive. However if you can, or get someone to rebore the pulley it’s far far cheaper to buy a metric motor. The pulleys can be extremely difficult to get off the shaft as they are aluminium.

If you choose a ‘nice’ small inverter you can then fit it inside the lathe which means they don’t need dust enclosures or shielding of the cables to the motor. Makes a lovely neat package rather than having the inverter screwed to the wall somewhere close.

 

[flh801978]

Deema
Please could you show a link to a single phase inverter to drive a single phase motor ?

IAN

 

[deema]

Here we go, many others

https://inverterdrive.com/group/AC-Inve ... 230Vac+1ph

 

[Tris]

Trying to get my head round vfd's, does doubling the supply frequency from 60hz to 120hz double the motor spindle speed and halving it (30hz) halve the speed?
Thanks in advance,
Tris

 

[flh801978]

Deema
Those type of vfd’s are only for fans or pumps with certain types of motors
Not the motors that are found on lathes or any other workshop machines(other than extractors)

 

[Paul Hannaby]

Trying to get my head round vfd's, does doubling the supply frequency from 60hz to 120hz double the motor spindle speed and halving it (30hz) halve the speed?
Thanks in advance,
Tris

Yes it does. For example one speed range on my lathe is from approx 450 - 1600 rpm and the frequency range to achieve that is 15Hz - 50Hz.

 

[RickG]

Hi, I have no experience in doing this on a lathe, but I'm an electrical engineer.
If you have access to a 3ph 415v supply then a 3ph motor will give you a smoother drive. It's a bit like having a single cylinder motorcycle engine Vs a 3 cylinder one.

If you don't have a 3ph supply, then I believe there are ways that you can run a 3ph motor on a 1ph supply. But I'm not a motors engineer, but you can Google it and there are sites that tell you how to do it... all the usual disclaimers apply!!

 

[deema]

Deema
Those type of vfd’s are only for fans or pumps with certain types of motors
Not the motors that are found on lathes or any other workshop machines(other than extractors)

You might be right for this application but I think the motor is only cap run rather than cap start which is why I suggested it. It’s been a couple of years since I had the motor out of my single phase UGrad. And I don’t remember it having a centrifugal switch.

 

[JWD]

Deema
Those type of vfd’s are only for fans or pumps with certain types of motors
Not the motors that are found on lathes or any other workshop machines(other than extractors)

i have an invertek optidrive e3 on my lathe and its perfect.. run with a 1.5hp dual phase 4 pole motor and it hasnt skipped a beat.

 

[graduate_owner]

I have a variable speed 3 phase inverter on my viceroy and I love it. I would definitely recommend that route. Safer too, because you can start at low speed if the work is out of balance. BUT -

1. you cannot have any switchgear between inverter and motor so you might have to bypass the existing on/off switch. Make sure the means of control is conveniently situated for safety.

2. low speed means a low speed on the cooling fan, so watch out in case you cause the motor to overheat. If space is not a problem you might be able to install a separate cooling fan and motor which always runs at full speed - not easy on a graduate tough

3. depending on the inverter, you might lose torque at low speeds.

Of course you won't be using low speeds all the time, just occasionally. I have the pulleys set to low spindle speed so I can use the inverter to run the motor at the highest speed for the job.

K