Union Graduate motor upgrade

[AlynJ]

Just acquired a Graduate lathe with 3/4hp 3 phase motor which I am going to replace as permanently wired in star mode so not suitable for 220V inverter, which I still need to purchase. I’ve heard that 3/4hp is somewhat limiting for this lathe, so may as well upgrade while I’m at it. Would appreciate any advice on what power to go for - 1, 1.5 or even 2hp?

 

[minilathe22]

3/4 HP is ok for spindle turning but for bowls on the outboard side I found it very limiting, especially during roughing out when it is harder to reduce the load on the motor.

I swapped for a 1.5HP 900rpm motor, which I found to make a huge difference. But I did add extra stop buttons to the lathe, I gave the impression it can do serious damage if clothing/fingers get caught!

Cheapest commonly available motor would be 1 - 2 HP 1400rpm. Bigger than 2 will most likely not fit in the motor space available.

 

[Myfordman]

You can get inverters that take 240v in and produce 415v out. Not common but they are out there if you look.
The other option is to pick open the star point and rewire the motor in delta and use a standard inverter.

 

[AlynJ]

Thanks, I did see a few 415V inverters but very pricy so took the plunge snd managed to rewire the motor to delta. Got it running off an Invertek E3 inverter, went for the 1.5kW model so future proof for a bigger motor later. Appreciate the advice and support.

 

[Myfordman]

Best prices for voltage converting inverters tend to be direct from China though ali-express.

 

[bigbigblue]

I am considering the same upgrade. Were there any issues in the end with the cooling, or was it all OK?
Cheers

 

[Spectric]

Hi

Do you mean a convertor, as invertors can only output 230Vac three phase due to being non linear and subject to EMC issues with harmonics but can provide speed control as frequency not fixed. A converter, digital these days can provide 400 three phase but at fixed frequency so no speed control. But for Aly a single phase motor with more Hp would be a good solution.

You can get inverters that take 240v in and produce 415v out. Not common but they are out there if you look.
The other option is to pick open the star point and rewire the motor in delta and use a standard inverter.

 

[Myfordman]

Hi

Do you mean a convertor, as invertors can only output 230Vac three phase due to being non linear and subject to EMC issues with harmonics but can provide speed control as frequency not fixed. A converter, digital these days can provide 400 three phase but at fixed frequency so no speed control. But for Aly a single phase motor with more Hp would be a good solution.

No I meant what I wrote.230v in 415 3 phase out and full speed control

 

[Spectric]

Hi AKA

Can you please provide some part numbers and suppliers because I have a use for an invertor that will give me both speed control and 400Vac output. I know I could run it from a digital convertor but that will not give me the ability to run the motor slower. I have tried finding one in the past but without success, and quote:

A phase converter varies the voltage in its conversion. It converts the voltage from 240VAC single phase to 415VAC three phase. The frequency in a phase converter is fixed at 50Hz so no motor speed control is available.

AC inverter drives are designed to control the speed of AC induction motors. They do this by varying the voltage and frequency being applied to the motor.
There are predominantly two voltage variants of AC inverter drive available:

- 230V single phase input, 230V three phase output
- 400V three phase input, 400V three phase output

references attached:

 

[Myfordman]

One make is Ecogoo. There are others if you look.
Can be bought direct from China using Ali Express or Banggood