dimmer switch.

[gordongp]

I have recently fitted a dimmer switch. Have noticed that after a period of time the switch heats up. Any suggestions?

 

[jj4091]

Do you really mean heats up, or that it gets a bit warm?

 

[gordongp]

Dimmer control warms up.

 

[Steve]

normal.

unless its too hot to touch, the plastic is deformed, and it has brown scorch marks, i wouldn't worry about it. all dimmers get warm.

 

[IJWS15]

Just to frighten some of the electricians on here..

I believe these dimmers use choppers (thyristors) and they use WATER COOLED power thyristors that turned 750 DC into variable voltage variable frequency AC.

 

[securespark]

Yeah, so?

 

[RF Lighting]

My car battery is full of water

AGGGGGGGH

Water and electricity do actually mix.

 

[systemtek]

ekkkk theres a live element in my kettle :O

 

[Adam_151]

Just to frighten some of the electricians on here..

I believe these dimmers use choppers (thyristors) and they use WATER COOLED power thyristors that turned 750 DC into variable voltage variable frequency AC.

Not quite a dimmer does indeed use a type of thyrister called a triac (which is basically two SCRs* back to back, or bigger dimmers might actually use two SCRs)

A SCR is a device which when triggered does not switch off until the current through it falls to zero, in a dimmer depending on the dim level selected, the SCR is triggered a certain amount of time after the zero crossing point and remains on until the next zero crossing point, there is one SCR for each side of the cycle.

(this is probably where you got the "chopper" term from, because it chops the waveform up, phase cutting dimmers would be a better term!)

The frequency remains as 50hz albeit with bits lopped out of it making it a nasty waveform and it can cause interference and buzzing, etc and distort the pf. There are parts of the circuit that are carrying pulsating DC (SCRs are DC devices, but as they are paired up [and very often in the same semiconductor package - called a triac- remember?]), its not as if they are feeding DC to the lamp or anything, and its not going to go any higher than 340v peak... not 750v

As for water cooled...I suppose there might be some fancy stage dimmers that are, I don't know, if its kicking out enough heat, then its as feasabke as water cooling a computer, but domestic dimmers... no

No



* people often think the term thyrister is interchangeable with scr, but SCRs are just a subset of thyristers, at least IMHO and thats what I'm sticking to!! (http://en.wikipedia.org/wiki/Thyristor)