240/12v Transformer loading values

Thread Starter

spike1947

Joined Feb 4, 2016
99
Hi Guys
I haven't been in the game for quite a while so seem to of lost some of my early days ways to calculate , so here goes , what will be the load if I have 4 x 12v/20w halogen bulbs ran from a 240/12v transformer ? ., ( I remember someone used to say to me in the past that with the 12V MR16 lamps that if the lamp was 20 watts it would draw 20watts more or less on the 240 side as well, is that correct?)

cheers

Spike
 
Last edited:
In theory 4 lamps is 80W but in reality, you lose say 10% as heat in the transformer and halogen lamps are not precisely 20W.
I have a few that measure around 23W and it does depend on mains voltage somewhat. If the transformer is oversized, say a 100VA part is will output a bit higher than 12VAC when underloaded at say 80W.
 

Thread Starter

spike1947

Joined Feb 4, 2016
99
In theory 4 lamps is 80W but in reality, you lose say 10% as heat in the transformer and halogen lamps are not precisely 20W.
I have a few that measure around 23W and it does depend on mains voltage somewhat. If the transformer is oversized, say a 100VA part is will output a bit higher than 12VAC when underloaded at say 80W.
Hi
Thanks for you reply , I really wanted to know if the halogen bulb was 12volt 20w , what wattage will be on the 240v line , will it be around the same 20W ? .
cheers
Spike
 
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