NA?Dimmers Use More Wattage?NA?

[coloradobluesky]

In Europe they rate internal combustion engines in kilowatts instead of horsepower. Both are units of power of course.

 

[flyingron]

ok but i just replaced every bulb in the house. all lites are dim able store brand from home deep,also EVERY lite is wired to older leutron skylark 600 watt dimmers . every thing works fine. sooo do i save on power when i dim the lites ??

Yes.

 

[GlennAB1]

I'm sorry Glenn, but that is 100% wrong. No "in the wall" dimmers were resistive. They would never have fit. The 1000W stage dimmers had plates over a foot in diameter. They did not work by increasing the dissipated power. As I described above, they were used in SERIES with the load and the added resistance overall, decreased the current flowing and hence (since voltage was constant) the power.

Power = E**2/R. E is constant (120V). Increasing the load resistance changes the power consumed in inverse proportion.

As I stated, the main reason resistive dimmers were problematic, is that you had to size the resistance of the dimmer with the load to get a nice full range of dimming. Often theatres had to add phantom loads if they need to dim a smaller instrument. Resistive boards are real antiques. I restored one at the Utopia theater in Greenbelt, MD. They were quickly replaced in practice with autotransformers which essentially was a continuously tappable transformer which was smaller (albeit not lighter) and simply modulated the voltage which was independent of the load.


Actually the frequency is constant, but they turn on conduction of the semiconductor device at different portions of the waveform depending on the dimmer setting (essentially varying the duty cycle). They still run at 60HZ.

Semiconductor dimmers are more efficient than resistive dimmers, but it's not the case that resistive dimmers consumed as much power while dimmed as they did at full brightness.

1000 watt stage lighting? WTF. You've obviously never performed maintenance on an aircraft lighting system. I have. Rheostats are very common. In a series circuit, adding resistance reduces voltage, that's what dims the light.

And I didn't say frequency (60 hz) was varied. I said the frequency of on/off was varied to control light intensity. (insert what Walter would say, here). Merry Christmas!

 

[Jim Rosenow]

ok but i just replaced every bulb in the house. all lites are dim able store brand from home deep,also EVERY lite is wired to older leutron skylark 600 watt dimmers . every thing works fine. sooo do i save on power when i dim the lites ??

Don't know about that, but the nice thing is you save every time you turn the lights ON! We're 100% LED and this particular fixture is the only one that gave us fits. We built the house to our specs, went energy-efficient on everything, and I'm annoyed if the electric bill gets over $100 a month.... and did I mention, electric ONLY...no propane, no natural gas. We're happy campers! Merry Christmas, all!!

Jim

 

[flyingron]

1000 watt stage lighting? WTF. You've obviously never performed maintenance on an aircraft lighting system. I have. Rheostats are very common. In a series circuit, adding resistance reduces voltage, that's what dims the light.

I have no idea why you think 1000 watt stage lighting is odd. Most household dimmers are good for 300W. Some 600W or more.
We're not talking about aircraft lighting. We're talking about household lighting. Your aircraft bulbs are a few watts, not 100 or more.
The total voltage DOES NOT VARY. The voltage across the bulb varies, but so does the current if you add a series resistance. Since the total voltage is the same, the whole system power consumed is REDUCED. Basic electrical theory.

And I didn't say frequency (60 hz) was varied. I said the frequency of on/off was varied to control light intensity. (insert what Walter would say, here). Merry Christmas!

I don't have any idea who walter is, but the FREQUENCY is UNCHANGED. What changes is the protion of the wave form that current flows in. As I said, it's duty cycle. Full on is 100% of the wave form. Half bright is 50%. The frequency is unchanged. The only time variable frequency is used is to control induction motor speed.

 

[GlennAB1]

A TRIAC turns off and on the electricity 120 times per second, twice per cycle, in a 60hz system. Adjusting where in the wave frequency that takes place, adjusts light intensity.

 

[3393RP]

They were quickly replaced in practice with autotransformers which essentially was a continuously tappable transformer which was smaller (albeit not lighter) and simply modulated the voltage which was independent of the load.

I consider an autotransformer one with a single coil which provides primary and secondary windings and has multiple taps. The desired output voltage is obtained by physically changing the tap point. What you describe as a "continuously tappable transformer" I call a variac. The variac is indeed able to produce any AC voltage between 0 and the incoming line voltage.

But this is just semantics. The variac is still an autotransformer.

 

[flyingron]

Yes, the "auto" in autotransformer refers to the primary and secondary wirings being shared. I didn't intend to imply the continously variable aspect was the "auto" part.

Variac is a trade name for a variable autotransformer. However, the term in the dimmer parlance is indeed autotransformer just as the other terms are resistance, triac (or semiconductor), or whatever. Since you're already talking about dimmers, the "variable" part is implied. House lights are frequently on something that looks more like a large variac. Autotransformer stage light dimmers don't look much different than many resistance boards other than being a lot smaller. A bunch of large levers and mastering done by mechanical interconnection.

 

[3393RP]

I used to take care of the critical electrical systems at a local TV station. Some of the legacy lighting and dimmers in the back junk room were crazy. It must have been close to a hundred degrees on the sets of early television newscasts.

 

[flyingron]

I used to take care of the critical electrical systems at a local TV station. Some of the legacy lighting and dimmers in the back junk room were crazy. It must have been close to a hundred degrees on the sets of early television newscasts.

Yeah, old TV cameras needed a lot of light. TV lighting all scoops and floods just put lots of uniform bright light on things.