3 phase AC motor control help

[nimeshasilva]

Hi all..

Is there any other way to control the speed of a 3-phase AC induction motor (ACIM) other than using an inverter? I mean, for example, a method such as, 3, single phase TRIAC control circuits combined together or something?

ON semiconductor had released a good app note (AND8011-D) regarding the single phase AC phase control, and the circuit is working like a charm. Now I need to combine 3 of them and control a small 3 phase ACIM. is it possible to do that? I think its worth asking before try.

Thank you

 

[tpetar]

This picture is just basic example using of triac :


Example:
Motor controllers

3 Phase AC Motor Speed Control | Circuit Diagram

 

[chuckey]

The single phase motor control is working by reducing the effective voltage to the motor, so the motor slows down. The problem is that the current will rise and the motor is effectively de-rated. A three phase motor works by the three phases setting up a rotating magnetic field which the rotor is trying to catch up with, lowering the voltages causes the same problem.
Frank

 

[nimeshasilva]

Thanx guys for the replies.
It seems its a ridiculous idea to speed control of a 3 phase motor using triacs. I'm giving it up.

Now I need to study more on Variable Frequency Drives instead..

 

[Tahmid]

Take a look at the dsPIC33MC series of microcontrollers and think about using it for your motor control. Your job will be made a whole lot easier. It's actually not too difficult once you thoroughly understand how it works.

Take a look here:
https://www.edaboard.com/threads/142271/
https://www.edaboard.com/threads/142271/#post810576
https://www.edaboard.com/threads/238042/

Hope this helps.
Tahmid.