Speed control of single phase induction motor

[Ed_Dinning]

Hi Gents, it is possible to run a single phase motor at variable speed with good starting torque, BUT, there are no commercial units available and it requires a very specialised dual inverter to feed the main and starting windings with variable frequency and voltage. The phase angle between these supplies must also be adjustable and the starting winding must be continuously rated.
A nice winters project for the power electronics types!

Ed

[ed731pdh]

I did have a book lurking around here where as I recall, it showed how to mod a 3 phase motor to run on single phase using capacitors. as usual, gone off the shelf when I want to look at it.

[AlanBeckett]

That's how I run my Chipmaster.

Alan

[dennishoy]

Folks...... Thank you ALL for your kind comments, help and suggestions.

Hi Gents, it is possible to run a single phase motor at variable speed with good starting torque, BUT, there are no commercial units available and it requires a very specialised dual inverter to feed the main and starting windings with variable frequency and voltage. The phase angle between these supplies must also be adjustable and the starting winding must be continuously rated.
A nice winters project for the power electronics types!

Ed

Ed's suggestion should work so I'm going to give it a try, but will not be modifying a single controller. Instead, I've bought a pair of Vacon VFDs cheaper than the current dry-jointed rubbish being imported from China. One will control the motor starting winding and the other will look after the motor main winding. Both drives will be running with different control parameters and one will be fitted with an interface card as I will need feedback signals to monitor and reduce the current to zero in the starting winding. The centrifugal switch arrangement will be disconnected assuming I can get the system running correctly. The phase angle betwen the VFDs can be controlled and adjusted with respect to one another and the frequencies can be locked together.

One rather useful feature of these Finnish made units is a remote control panel (RS232 link) so the uniits can be hidden away. Once set up, only one control panel is needed and this will be fitted to the lathe.

There is also a nice piece of software for adjusting the parameters and monitoring the VFDs when running. Vacon make some very nice equipment, but unfortunately, all the equipment appears to be designed to drive only three-phase motors.

I've attached a couple of pictures showing the small size of the VFDs and also the remote control panel. Wish me luck....

[dennishoy]

The manual is uploaded here, for those interested in learning a bit more about what these versatile units can do.

[Ed_Dinning]

Hi Dennis, looks like I've started something here (pun intended). Let me know how you get on.

Ed