Roman12 Posted October 12, 2016 Share Posted October 12, 2016 I have just purchased a couple of R911 power units which are probably 20+ years old. I was wandering what the fuse in the mains plug should be. Can anyone help.Thanks Link to comment Share on other sites More sharing options...
Chrissaf Posted October 12, 2016 Share Posted October 12, 2016 This is a R911 controller../media/tinymce_upload/7ef38ab2e4252994849f844d010e1527.jpg.The label of the R911 states an output of 14.3 volts @ 1.1 amps. The answer to your question is simple ohms law mathematics..The output wattage is 14.3 volts x 1.1 amps = 15.73 watts (rounded up to 16 watts)The input wattage = the output wattage plus internal power (wattage) losses. For the purpose of this calculation let us assume that there are no internal controller power losses. Thus input W = output W..Thus if input power = 16 watts and the input voltage is 240 volts, then the input current = 16 watts divided by 240 volts = 0.067 amps or 67 milli-amps..Standard UK plugs, to the best of my knowledge have a minimum obtainable fuse rating that you can buy of 1 amp which is 1,000 milli-amps. The smallest value fuse that is commonly available is typically 3 amp (3,000 milli-amps). So either way, both fuse values are far more than you need. The safest value to use would be 1 amp..Here is an example of a 1 amp fuse supplier here in the UK, but any electrical component retailer / wholesaler should stock them..https://www.tlc-direct.co.uk/Products/MK0601.html Link to comment Share on other sites More sharing options...
Roman12 Posted October 13, 2016 Author Share Posted October 13, 2016 Many thanks for the detailed explanation Link to comment Share on other sites More sharing options...
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