3 phase Ac motor speed controller circuit required

[Ali Sajjad]

can anybody provides a basic circuit for controlling speed of 3 phase AC motors ?

 

[Styx]

What type of AC machine?

There are two types
1) Induction machine
2) Syncronous machine

As to a basic cct for speed control if there was such a thing I would probably be out of a job

There is no info here abt what the machine needs to do?

what speed range
How much torque does it need to provide over the speed range
What is available for position determination.

 

[stevez]

You might find manufacturer's literature and possibly repair manuals with schematics for this equipment by looking at their websites or by contacting them directly. You might also find a decent explanation on how their unit operates as well as block diagrams that might help you to understand.

Most AC motors require a variable frequency drive for speed control. I've never seen a simple schematic for even a single phase version- again that is simple.

 

[tavib]

The most used AC machine as motor is asynchronous type or induction.
The only efficient way to control speed on these machines is to control the frequency of current applied to motor.
This can be done in some ways depending especially by the power involved.
In old systems the motor-generator group are used, especially in high power systems. This is big and high cost solution.
In new systems and for low power the electronic 3 phase inverter can be used for create a synthetic 3 phase netwotk with frequency controled. This is done by using 6 PowerMOSFETs(2 for eatch phase) a drive circuit for all 6 MOSs and a command circuit that usualy is assigned to one microcontroller witch must be drive by a program whitch create the syntetic 3 sinus at 120 degree one for other.
To create a system like that need a lot of work.

 

[Ali Sajjad]

thanx everyone for ur help. I need further help in this regard. if ne one of u does have such type of circuit's diagram (however complex it might be), please send this to me. I can not manage to go to a vendor for such diagram, neither i can trace as-built of a system already installed somewhere. If this could be possible, i shall be very much thankful u.

 

[Styx]

The most used AC machine as motor is asynchronous type or induction.
The only efficient way to control speed on these machines is to control the frequency of current applied to motor.

That may be the case. But variable speed inverters for syncrounous drives are becomming extreamly competative against the traditional workhorse of industry - the squirral cage induction machine.

just a final point.