not entirely true, but not entirely false either, it's just adding to the confusion because 2 types of AC motor are being spoken of here with two different types speed controllers as though they are one in the same. AC VSDs adjust the speed of a AC syncronous motor by adjusting the frequency. these types of electric motors, the speed is set by the frequency of the AC power source. the above jaycar speed controller uses a triac to control the amount of AC power delivered to a AC induction motor. most household mains powered AC motors are of the AC induction motor type.Hi MAH,
This sort of stuff is right up my alley. Slowing down an AC motor without a significant loss of torque requires a Variable Frequency Drive. An AC motors speed is mainly governed by the 50 hertz ac power it is supplied, but in the case of a VFD, the AC is converted to DC then reconverted to an AC signal of the frequency of your choice.
The Jaycar kit your looking at will only only alter the average voltage not frequency, and will therfore only succeed in reducing torque to the motor not the speed.
Only in the case of some AC fans and split pole motors, this decrease in torque will result in a decrease in speed.
I'm guessing your thinking of using it on a grain mill, so I would say it will be totally unsuitable.
I hope I didnt bore you too much with the BS theory.