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speed control of induction motor using triac

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A triac dims the light from an incadescent light bulb or the heat from a heater.

An induction motor needs to have the mains frequency changed somehow to change its speed.
 

If it is a single phase induction motor like ceiling fan motors, you can use Triac (voltage control) to control its speed.
Check these **broken link removed**
**broken link removed**
 

speed control of induction motor

hello , i have Zero crossing detector and i am using BT - 136 triac with moc 3021 optocoupler . but i am not getting exact output can anyone help to me.
 

Re: speed control of induction motor

The RPM of an induction (brushless) motor is directly proportional to the mains frequency ..
To control the RPM one have to vary the frequency, not the voltage; google for VFD (variable frequency drive) or VSD (variable speed drive) ..

A circuit with a triac and optocoupler is useless in this application ..

Rgds,
IanP
 

While I agree in general with the cautionary comments above, SOME line powered induction motors can be controlled by a thyristor-type speed controller, as indicated by the common ceiling fan speed controller. However, this only works with purpose-designed motors in specific applications (ceiling fans, for example) with appropriate load speed/torque relationships and requires a controller designed specifically for motor control, not lighting control. Motors intended for such speed control are tolerant of high slip (difference between motor speed and synchronous speed).

So I think the appropriate question for kalt solutions is what specific motor and application are you trying to control?

awright
 

Indeed, such 3phase motors exist. They are designed with increased rotor resistance.
The torque delivered is quadratic with the average voltage applied to the motor.
An application is for example a system where you want to regulate the torque and not the speed of the motor.

For the power stage, a triac can be used, but for a more robust system, an alternistor can be chosen. It should be a more robust solution. Internally, an alternistor has two (seperate) thyristors wired in anti-parallel.
 

The control of rotor speed of an induction motor can be done in different ways:-
1) Rotor resistance control
2) Variable frequency control
These are techniques that i know to myself. If any one of u knows plz reply to my gmail id plzz
maruthinarasimha8@gmail.com.
But perfect speed control of Induction motor cannot be obtained by TRAIC, it must require some external circuit to control it. If any one knows abt perfect speed control of induction motor plz reply to my gmail id.
 

Hi,
There are a few problems. You may not notice this as the motor you used as load is not that high a load.
When you use phase angle control, you ARE controlling the SPEED, but you're also lower the torque. By phase angle control, you control voltage, and in turn torque is not constant and may/will cause a problem with large loads on the motor. The proper way to do it is constant V/f technique, where you change the frequency as well as the voltage. This can not be done with triac and is usually done with SPWM after rectifying the AC mains to DC.

Take a look at these very carefully:
http://ww1.microchip.com/downloads/en/AppNotes/00843a.pdf
http://ww1.microchip.com/downloads/en/AppNotes/00887a.pdf
http://ww1.microchip.com/downloads/en/AppNotes/00967A.pdf
**broken link removed**
http://www.atmel.com/dyn/resources/prod_documents/doc7545.pdf

Hope this helps.
Tahmid.
 

Hi,
There are a few problems. You may not notice this as the motor you used as load is not that high a load.
When you use phase angle control, you ARE controlling the SPEED, but you're also lower the torque. By phase angle control, you control voltage, and in turn torque is not constant and may/will cause a problem with large loads on the motor. The proper way to do it is constant V/f technique, where you change the frequency as well as the voltage. This can not be done with triac and is usually done with SPWM after rectifying the AC mains to DC.

Take a look at these very carefully:
http://ww1.microchip.com/downloads/en/AppNotes/00843a.pdf
http://ww1.microchip.com/downloads/en/AppNotes/00887a.pdf
http://ww1.microchip.com/downloads/en/AppNotes/00967A.pdf
**broken link removed**
http://www.atmel.com/dyn/resources/prod_documents/doc7545.pdf

Hope this helps.
Tahmid.

MR TAHMID, u r very much right VF is the proper way to control the speed of an Induction motor & i know that very well, the biggest disadvantage of using Phase Angle Firing Control is reduction in torque, but man all small cheap machines uses "Phase Angle Firing Control" Technique . . . MR TAHMID BUILT ONE VARIABLE FREQUENCY AC MOTOR DRIVE & SHOW ME i wanna see . . .

YouTube - Brushless AC Servo Motor Driver PI controller via PIC18F1320
 

Hi,
You're right in that it's fine for small motors. But not for industrial. I'm studying the topic and am in the phase of developing one. It may take some time, so I'll post a pic/vid when done. It's a complex design of plenty of commercial demand, so needs a lot of studying and is not the easiest to implement.

Thanks.
Tahmid.
 

Hey Tahimid bro,
I’m also working on VF Drive, I got success in making one Variable frequency Single Phase Sine Wave Inverter. dude its not that much tricky
 

Hi,
The single phase maybe not, but the 3-phase seems quite tricky to me. Can you describe how you implemented VF drive, using which controller, and the method?
 

Microcontroller: PIC16F876A (Hi-Tech C Compiler)
Topology used: Sinusoidal Pulse Width Modultaion

bro soon i will upload the video

MOD: I see you ulpoading your video's or suggesting the youtube video of your projects. But just showing video does nothing but advertising yourself and your products. So you may continue that in the advt section meant for.
 
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    mikch

    Points: 2
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i have a problem in this project 2...sir do you have a circuit diagram of single phase induction motor controller?...if you dont mine can you give me a working circuit of this one..if it is ok to your sir....thanks....
 

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