Phase Dimmer Control using Triac

Dinesh's picture

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Joined: Aug 29, 2019

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Phase Dimmer Control using Triac
August 29, 2019 - 3:10pm

Hello Sir/Madam,

I am engineering student making phase dimmer control using triac

The schematic is as attached

What I have observed that many times attached circuit stop working due to failure of triac

I am not sure is it because of di/dt or dv/dt failure.

In order to avoid this I have used triac of much higher rating (10A) even though current needed can be as low as 1A.

However the problem continues. I have observed that the failure is for transformer powered halogen lamp (inductive load?) and for ceiling fans.

It works satisfactorily for incandescent lamps.

Also I am sharing one more observation that if I connect glass tube fuse link in series with the load then the fuse blows.

From the various information available I realized that I need to use choke / inductor to overcome this problem. Is that right?

I need help to

1. To find out the value of the inductor for 0.5A, 1A and 2A

2. Is this a special type of inductor? if yes wish to know make

Thank you in advance

Dinesh

Ashutosh's picture

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Joined: Aug 27, 2018

Replies: 12
Triac Phase dimmer
August 30, 2019 - 11:05am

You circuitdiagram is missing it hard to answer the question without that, but still will try....

In order to avoid this I have used triac of much higher rating (10A) even though current needed can be as low as 1A.

This is over engineering, you probably need 25% more than peak current of yor load. 10A is more than enough

However the problem continues. I have observed that the failure is for transformer powered halogen lamp (inductive load?) and for ceiling fans.

Inductive loads like motors are the most notorious ones beacuse they induce a back EMF (reverse voltage) back into the TRIAC if there are not protection circuits the it will damage the TRIAC

Also I am sharing one more observation that if I connect glass tube fuse link in series with the load then the fuse blows.

What is the rating of the fuse and where exactly did you connect it? after the switching side? 

From the various information available I realized that I need to use choke / inductor to overcome this problem. Is that right?

Not sure because we dont know your circuit yet. Also have you considered a snubber circuit?