lathe speed control

[cmoscache]

i need some design ideas for a lathe speed control. It has a 120v/60Hz 1HP motor. I need to be able to control the freq. or current at a stable level. A regular triac motor speed control is not stable enough. Any help will be greatly appreciated.

 

[Mikebits]

My lathe has a DC motor with a PWM speed controller.

 

[cmoscache]

i built this one from scratch. It does well with small dia. stuff but I want to slow it down and try some larger stuff.

 

[Mikebits]

Perhaps you could change your pulley size.

 

[Hero999]

You could try a variable speed drive but the problem is they don't work for single phase motors because the starting mechinism if frequency dependant.

The best way would be to replace the motor with a universial which will work with a phase controller.

 

[jpanhalt]

Presumably, that is a single-phase motor. Is it split phase, capacitor start, brushed? Brushed motors can be controlled easily as you suggest. The others can sometimes be controlled, but at a great loss of torque. Check out KB Drives.

My recommendation is to switch to a 3-phase motor and use a 1-phase powered VFD or switch to a DC motor and use a DC controller. The DC controller will be a little cheaper (about $100 on eBay), but the motor is more expensive. I have done it both ways. The DC option may give a little more constant speed, but the difference is slight.

John

 

[Diver300]

You can remove the capacitor from a capacitor-run or capacitor-start single phase motor and run the motor from a variable speed drive. The variable speed drives take in single phase and output 3-phase, variable frequency.

I have even seen 3 phase motors run as single phase by adding a capacitor, so changing to 3 phase means you can get a bit more power out of them.

 

[jpanhalt]

You can remove the capacitor from a capacitor-run or capacitor-start single phase motor and run the motor from a variable speed drive. The variable speed drives take in single phase and output 3-phase, variable frequency.

How do you connect the three phases from a VFD to a single phase coil, assuming you have one motor coil and one starting coil, like this?


Second, not all VFDs can be powered by single phase.
John