Electrician Talk banner

1 - 20 of 21 Posts

·
Registered
Joined
·
2,219 Posts
mxslick said:
If the dimmer and transformer are both listed for the application I see no problem at all.

Cinemas frequently dim transformers for aisle lighting.
Do they "dim" the circuit before the xfmr or after the xfmr?
 

·
Registered
Joined
·
10,316 Posts
Discussion Starter #10
So, your saying that by doing this a typical 100watt Home Depot $59 transformer may last 6 months instead of 1 year then? How is it hard on it? Are the flux angles part of this ?
 

·
Registered
Joined
·
1,611 Posts
BBQ is talking about electronic dimmers with Triacs in them. If it's under 1000w you can just use a rheostat.
 

·
Salty Member
Joined
·
31,081 Posts
BBQ is talking about electronic dimmers with Triacs in them. If it's under 1000w you can just use a rheostat.
A what? :blink:

I mean yes I know what they are, but I don't think I can get one for a wall switch.
 

·
Bilge Rat
motors and controls.........
Joined
·
7,084 Posts
The dimmer Bob is talking about is designed for inductive loads. It will work for resistive, but a dimmer designed for resistive loads will cause the transformer (or the dimmer) to fail early, and it'll be noisy.
 

·
Registered
Joined
·
4,665 Posts
As long as there are just incandescents connected the transformer, I don't see an issue with it.
Incandescents or LEDs doesn't matter. Both will dim nicely with the proper equipment.

Of course, you don't want to try to dim motors or other general purpose loads connected to a transformer. :)

Do they "dim" the circuit before the xfmr or after the xfmr?
Dimming is done on the primary side of the transformer. There are some cases (very rare) where a dimmer or voltage control would be applied at the secondary, but not a common practice.
 

·
Registered
Joined
·
31,174 Posts
We use Variacs for controlling transformers. I have a 5kva Variac, that we can step voltage from '0" zero to 580, makes some testing easier to be able to control the voltage.
 

·
Registered
Joined
·
12,167 Posts
Dimming is done on the primary side of the transformer. There are some cases (very rare) where a dimmer or voltage control would be applied at the secondary, but not a common practice.
If you know the reason for that, would you please share it? Thanks.
 

·
Donuts > Fried Eggs
Joined
·
17,054 Posts
...It will work for resistive, but a dimmer designed for resistive loads will cause the transformer (or the dimmer) to fail early, and it'll be noisy.
I learned this when I tried to put a speed control on my blender.

Worked fine until the day it didn't, and then I was cleaning milkshake off the ceiling.
 

·
Registered
Joined
·
1,611 Posts
A what? :blink:

I mean yes I know what they are, but I don't think I can get one for a wall switch.
Used to :p Haven't installed one in a while so I don't know. This appears to be one.



If you know the reason for that, would you please share it? Thanks.
Most likely so you don't have to dissipate all the power on the secondary which is usually a much higher current.
 

·
Registered
Joined
·
4,665 Posts
If you know the reason for that, would you please share it? Thanks.
triden beat me to it but his answer is correct:

Used to :p Haven't installed one in a while so I don't know. This appears to be one.





Most likely so you don't have to dissipate all the power on the secondary which is usually a much higher current.
LOL and that picture is of an ordinary triac based dimmer with a rotary knob.

A rheostat is a much larger animal and features such cool things as exposed windings and massive amounts of heat dissipated. :laughing:

Something like this:




Ones used for lighting are much larger (a 1kw rated one is about 8-10" in diameter).
 

Attachments

1 - 20 of 21 Posts
Top