Ac Motor Speed Controller

[user 384]

Any electrical folk out there know much about these speed controllers from Jaycar? Specifically if I used it on a 500w motor to make it run slower would this significantly affect the torque of the motor?

Cheers
MAH

 

[vlbaby]

Any electrical folk out there know much about these speed controllers from Jaycar? Specifically if I used it on a 500w motor to make it run slower would this significantly affect the torque of the motor?

Cheers
MAH

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.

cheers :beerbang:

vl.

 

[sintax69]

have this same controller which i used for my mill and it is not much good for low down torque i was using it on a drill to drive the mill and it just stalled all the time

 

[jupiter]

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.

cheers :beerbang:

vl.

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.

edit:
just a quick reference link:
http://en.wikipedia.org/wiki/Electric_motor
gottalovewiki

 

[AUHEAMIC]

Spot on Jupiter

I'm in the VSD game and just to add to what you have said it is possible to control a 3 phase synchronous motor with a 240 volt single phase power supply provided the 3 phase motor is dual voltage. IE 240 volt delta connection, 415 volt star connection. You can tell if a 3 phase motor is dual voltage by the number of terminals (studs) in the terminal box. In Australia a dual voltage 3 phase motor has 6 terminals. The 240 volt input VSD splits the single phase into 3 phases so if the motor is wired in 240 volt delta connection it will run fine.

 

[Wortgames]

Hi MAH, depending on what you plan to do with it, a gearbox may be a better way of reducing speed without reducing torque (in fact you'll increase it).

Jaycar has some small gearbox kits but you could also try industrial bearing suppliers etc - maybe give the yellow pages a go.

 

[vlbaby]

I assume you have a single phase induction motor MAH, so you could use a VSD to do the job, but its' too damn expensive. I'd go with wortgames suggestion and reduce the rpm by a gearbox of some kind, or even a pulley system etc.

cheers

vl.