I have a Crompton Greaves single phase induction motor that powers my drill press (image below). I believe it’s rated at 1/2HP. I wanted to control the speed of this motor so that I can use the drill for tapping operations too. I’m guessing a VFD would be the way to go? If yes, how do I connect this motor to the VFD? Also would a VFD rated for 0.75KW work?
Best Answer
Single-phase motors do not perform well with any type of speed control. The motor in question is particularly problematic because it has both a start capacitor and a run capacitor. The start capacitor must be disconnected above a certain speed when the motor is started.
There are few manufacturers (perhaps only one) that make VFDs for single-phase motors. Initially, the VFD for single-phase motors was sold only to drive centrifugal pumps and fans. Only single-capacitor motors were said to be suitable. More recently, they may have expanded their recommendations.
You will probably find that the best alternative is to buy a three-phase motor and a VFD from one of the many manufacturers that sell VFDs for three-phase motors. Many VFDs with ratings up to at least 2 Hp are available for use with single-phase input power at 220-230V. There are some lower power VFDs for 120V single-phase input and 220-230V 3-phase output.