Need a 240V to 120V 100W transformer?

Question

Hi,

I'm looking for a transformer which I can use wto run an old American computer monitor here in the UK. The monitor has a label which says 120V and 85W MAX.

Could someone advise me if such a transformer is stocked here? Preferably one which is reasonably stand alone and does't require additional wiring?

Many thanks.

beacon_dave · Answer

Always difficult to tell without having it on the bench to actually measure. I seem to recall that over here at least electrical products drawing in excess of 500mA need to have their PF substantially corrected. Not sure when that rule came in or if it was internationally adopted. However from previous tests with my budget power meter it appears to be true. Also the 85W referred to was specified as a maximum rating which probably means peak power draw at on switch-on and not continuous. There is the Block TIM200 TIM200 which is rated at 200VA but price jumps up again TIM200 - BLOCK - Isolation Transformer, Class II, 200 VA, 1 x 230V, 2 x 115V, 860 mA | Farnell element14

shabaz · Answer

Hi, It's exactly that. Easier described as out of phase as you say, although in practice it happens due to non-sinusoidal waveforms too. The power the device (computer monitor in this case) consumes will be given off as heat, and that is marked on the monitor in Watts. However, the apparent power could be larger. Plus there is a certain efficiency for the transformer (85% in this case I think - not looked again at the spec sheet). I've no idea what the power factor is (was), but I found this on google books: It would suggest that there is quite a lot of variance, but maybe 0.6 or 0.7 would be a good number to choose. So, that means 120-140VA but at 85% efficiency 140-160VA is more appropriate.

beacon_dave · Answer

Autotransformer SAT200 - BLOCK - Auto Transformer, Class I, 115 VAC, 200 VA, 1.74 A | Farnell element14

Need a 240V to 120V 100W transformer?

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