3 phase to single lathe

[Hood]

I've put a switch on my clutch so when is disengaged it stop the motor so i get a slow spool.

I have a servo motor on mine and although I direct drive to the spindle so not quite the same but I have rigged up switches to the saddle lever to start the fwd/rev of the motor. It works well and I can see no reason similar could not be done with a VFD.

Vid here.

 

[mtt.tr]

I have a servo motor on mine and although I direct drive to the spindle so not quite the same but I have rigged up switches to the saddle lever to start the fwd/rev of the motor. It works well and I can see no reason similar could not be done with a VFD.
View attachment 288984


Vid here.

Its on my list, has been for a good while.

 

[Jacktegla]

Thanks for all the replies I think its a bit big so I will keep on the lookout for a smaller motored lathe

 

[m_c]

I've got a generic Chinese 2.2KW VFD driving a 1.5KW motor and it's very easy to trip the power overload if I'm too clumsy turning it on or engaging the clutch.

So I'd be wary of the veracity of that "10hp" claim.

The issue is VFDs are not that tolerant of overloading.
When you dump the clutch in, you are probably overloading the motor quite a bit, which with a normal thermal overload switch, isn't really a problem, as they need either a lot of overload over a short period of time, or less overload over a longer period of time before they'll trip, as they are designed to stop the motor from overheating due to overloading, not protect it from sudden overload (if you were to short out the motor terminals, you'll probably find the fuses upstream of a thermal overload will blow, before the overload trips).
A VFD typically only allows for 150% overloading, which suddenly connecting a lathe drive/chuck to an already spinning motor is likely to be exceeded, and I'd hazard a guess will put a momentary overload of 2-300% on the motor, as it'll essentially be near stalling the motor.

It's why for the OPs query, I'd say ditch the original control, and connect the motor directly to a suitable VFD. That way the VFD can soft start the motor, and you don't have to factor in any sudden loads, which would require a grossly oversized phase converter to handle without tripping anything out. For safety, I'd also suggest fitting a braking resistor so the spindle can be stopped quicker under control, rather than just free wheeling to a stop.

 

[Spark plug]

The issue is VFDs are not that tolerant of overloading.
When you dump the clutch in, you are probably overloading the motor quite a bit, which with a normal thermal overload switch, isn't really a problem, as they need either a lot of overload over a short period of time, or less overload over a longer period of time before they'll trip, as they are designed to stop the motor from overheating due to overloading, not protect it from sudden overload (if you were to short out the motor terminals, you'll probably find the fuses upstream of a thermal overload will blow, before the overload trips).
A VFD typically only allows for 150% overloading, which suddenly connecting a lathe drive/chuck to an already spinning motor is likely to be exceeded, and I'd hazard a guess will put a momentary overload of 2-300% on the motor, as it'll essentially be near stalling the motor.

It's why for the OPs query, I'd say ditch the original control, and connect the motor directly to a suitable VFD. That way the VFD can soft start the motor, and you don't have to factor in any sudden loads, which would require a grossly oversized phase converter to handle without tripping anything out. For safety, I'd also suggest fitting a braking resistor so the spindle can be stopped quicker under control, rather than just free wheeling to a stop.

I’ve just tested your theory while standing in front of my lathe, it has a handy amp meeter to monitor motor load

At idle the motor draws about 7 amps but when I engage the clutch with the lathe in the highest speed the current draw peaks at around 20 amps before dropping back to around 8 amps or there about.

So you weren’t too far away.

 

[skotl]

I’ve just tested your theory while standing in front of my lathe, it has a handy amp meeter to monitor motor load

At idle the motor draws about 7 amps but when I engage the clutch with the lathe in the highest speed the current draw peaks at around 20 amps before dropping back to around 8 amps or there about.

So you weren’t too far away.

Well, that explains it!
I just need to be a bit less heavy-handed with the clutch.

 

[Spark plug]

Well, that explains it!
I just need to be a bit less heavy-handed with the clutch.

I was quite surprised actually, but it makes sence now that I think about it.

The current draw during the acceleration phase was rather moderate, but the big spike came when the spindle archived its running speed and I imaging the motor was suddenly unloaded then for a split second turns into a generator. This I’m guessing is what upsets the inverters.