low voltage downlighter ampage

[johnnyjb]

Since if you have a 12 volt 50 watt light it will pull 4.1 amps for a single light wouldnt you need a bigger mcb than 10 amp B type,6 amp switches if you had a few rooms with these lights installed or does the traffo play a part in all this

 

[Lectrician]

A 50 watt lamp will draw 4 ish amps at 12v.........but hoiw much on the 230v side

 

[Space cat]

To understand what's going on you need to know how a transformer works. In an ideal transformer two things are the same on each side: the volts per turn and the amp turns. That's because both windings are wrapped around the same magnetic field and every turn sees the same field as every other turn.

The turns ratio determines the voltage ratio, in your case 230 : 12. Since the amp turns must also be equal, the ratio of currents is 12 : 230 and that makes the primary current 4.1 x 12 / 230 or about 220 mA.

Real transformers aren't perfect. They have primary inductance which takes extra current (though no extra power). Winding resistance wastes some of your voltage and, get this, the core itself absorbs energy every time the magnetic field reverses, but these losses are small compared to the output power.

Most of the 'transformers' sold today are nothing of the sort. They're switch mode power supplies but buried inside them is a small transformer running at a very high frequency. The voltage and current ratios still apply.

 

[ricicle]

Winding resistance wastes some of your voltage.

Copper losses

the core itself absorbs energy every time the magnetic field reverses

Hysterisis losses

Don't forget the Eddy current losses also...

 

[securespark]

Hysterical losses?

 

[Steve]

Hysterical losses?

I was just thinking that! Before I read your post! I was thinking what sort of joke i could make out of it

 

[bernardgreen]

Good old Eddy Currents...... the chap who is always stealing joules...