Posted by Jim Greenhill on 18/01/2018 14:50:40:
Hi I have been reading about vfd on a number of posts/ forums, I can see the attraction for speed control, but what I don’t understand is the reasons to change motor to three phase, and why doing so reduceds the noise. Why not put speed control on single phase motor
Jim
A single phase motor works a little like it's kicking a can down the road – one power feed pulsing 50 times a second. It's a useful compromise for smallish motors in a domestic situation.
A three phase motor has three power feeds each off-set from the others by 1/3rd of a cycle. The windings are arranged to create a smoothly rotating magnetic field. Speed control is achieved by varying the frequency of the supply. Altogether 3-phase motors are a much better solution apart from needing a 3-phase supply to run one. These days, that's much easier and cheaper than it used to be – a VFD,
You can speed-control a single-phase motor but it's done by increasing the can-kicking effect. Even noisier and the motor loses lots of power and torque. Not a good idea.
Dave