Transforners

[johnnyjb]

This might seem like a stupid question but how do energy effecient downlighters with a transformer save on bills.I cant understand what kinda current would be pulled by the transformer.Its bein stepped down by transformer so its takin more than 12 volts or 7 watts or whatever they take

Im a spark but its buggin me.It was explained in college but its gone out of my head

 

[bernardgreen]

The ideal transformer does not waste power but the ideal (perfect) transformer has yet to be designed.

how do energy effecient downlighters with a transformer save on bills

They save because they produce more light per watt of electrical energy than "ordinary" lampsl For the same amount of light you need to use less electricity. This applies to all energy effecient lights.

Only if the lights low voltage do you need a transformer.

 

[RF Lighting]

Are you confusing low energy downlighters with low voltage downlighters?

 

[Steve]

This might seem like a stupid question but how do energy effecient downlighters with a transformer save on bills.I cant understand what kinda current would be pulled by the transformer.Its bein stepped down by transformer so its takin more than 12 volts or 7 watts or whatever they take

Im a spark but its buggin me.It was explained in college but its gone out of my head

energy efficient low voltage downlighters have yet to be discovered AFAIK mate.

energy efficient downlighters are mains voltage, and they use about 20% of the energy of a standard 50 watt downlighter for a similar light output.

low voltage downlighters run on 12 volts and pull 20 or 35 or 50 watts, with light output varying approximately in proportion with wattage. They are not energy saving. Due to the lower voltage, the current drawn is higher, and therefore they often need very chunky cables to be used.

a watt is a watt is a watt, at any voltage. do not confuse wattage (power) with current.

 

[Job_n_knock]

Here's something I fail to see. Whatever energy efficient devices we use, however many times we turn "that" light off when we dont need it. How does this save the planet? I know it saves on Elec. bills on the consumer side but to me, whatever you do, that generator still spins at the same speed and it uses just as much fuel to create steam for the turbine.
It makes no difference as far as I can see.

 

[RF Lighting]

Have you ever used a small portable generator?

If you stick a 50W load on it, the gen set keeps running like it was.

If you stick a 2kW load on it you will hear the gen set start to work harder.



This is the same with the grid / power stations.

The more power is used the harder the generator has to work, so the more energy is required to turn it. (it is a bit more complicated than this but you get the idea)


http://www.dynamicdemand.co.uk/grid.htm

 

[Job_n_knock]

Interesting.
I like the Power balance meter website

Thanks mate

 

[Steve]

If my car is stationary with the engine ticking over, and I turn on the heated windscreen and the heated rear window, the engine's revs drop slightly, because the alternator is putting more load on the engine.

 

[securespark]

Serves you right for buying a Ford!

Miaow!

 

[johnnyjb]

So what your trying to say is ifi have a 12 volt downlighter with a transformer (obviously) 50 watt bulb my current would be 4.1 amps

I did the sum V=P*I and used the secondary (12) voltage for v


I must be wrong cause that seems alot for one light

 

[securespark]

Yup. Which is why you have to be careful running SELV a distance or running several lamps worth down one cable.

 

[IJWS15]

Remember I squared R - same reason the Grid runs at hundreds of KV.

Higher the I higher the resistance loss!