Hello Everyone,

I’m a retired USAF Lt Col 25 years in service and 20 years as Industrial Electrician. I have always tinkered with electronics but this project is above my pay grade. I need some help. I have a single phase 120v 60Hz ¾ HP drill press I wish to convert to a homemade VFD controlled by Arduino. I found this circuit on http://www.homemade-circuits.com/2013/09/single-phase-variable-frequency-drive.html. Please see attached image.


With my limited understanding of what is happening here, I think everything to the left of the4017 (IC3) can be replaced with the Arduino. I know it is a big ask however I need help with the schematic and programming. Any help will be greatly appreciated.

 

Hello there,

Are you sure that is the right schematic for a regular AC motor? It looks like it might be made for a special kind of motor.

Normally you would use either a half bridge and split supply (or split capacitors) or a full bridge which would provide excellent support for almost any AC load you can think of.

Also, your drill press may have a motor with brushes as many motors for stuff like that have. If it does, you can get away with a triac controller similar to a light dimmer. The VFD is needed mostly for AC only type motors.

Microcontrollers can take the place of a lot of logic.

 

Single phase induction motors do not run well away from their design frequency. You would be better off replacing the motor with a three phase motor and three phase VFD. It would probably cost more to buy the parts for a VFD than buying one ready made. (Plus the fact that you would probably destroy a lots of power switching devices in the proccess of getting it working.)

Les.

 

I agree, I think you are wasting your time trying to provide VF to a 1ph induction motor, they tend to drop out of run at low rpm and under load.
Either a 3ph/VFD combo as suggested or a T.M. DC motor might be the better choice.
Max.