12V INVERTER

[JohnW2]

Indeed, so for the suggested 1.2 ohms, it would need to be greater than the suggested 100W.

Who on earth suggested a 100W rating for the resistor? (not me, and no-one that I noticed!) Even at 12V, a 1.2Ω resistor would dissipate 120W!

Kind Regards, John
Edit: typo corrected

 

[Monkeh]

Indeed, so for the suggested 1.2 ohms, it would need to be greater than the suggested 100W.

Who on earth suggested a 100W rating for the resistor? (not me, and no-one that I noticed!) Even at 12V, a 1.2W resistor would dissipate 120W!

Kind Regards, John

Top of page 2.

 

[JohnW2]

Who on earth suggested a 100W rating for the resistor? (not me, and no-one that I noticed!) Even at 12V, a 1.2W resistor would dissipate 120W!

Top of page 2.

Ah - in a link, rather than text - apologies for not having noticed that.

So, yes, for a 1.2Ω resistor. that would be far too low a power rating at 12V, let alone 12.6V or 13.4V (or more).

Kind Regards, John

 

[davelx]

Indeed, so for the suggested 1.2 ohms, it would need to be greater than the suggested 100W.

Who on earth suggested a 100W rating for the resistor? (not me, and no-one that I noticed!) Even at 12V, a 1.2W resistor would dissipate 120W!

Kind Regards, John

Easy enough to use 4 in series/parallel to give 1.2Ohm 400W.

 

[JohnW2]

Easy enough to use 4 in series/parallel to give 1.2Ohm 400W.

Indeed so, or any other of an large number of possible combinations of values & power ratings to get whatever value/rating one wants. The discussion (rather than the link) had mentioned nothing about power rating, and I had asumed that everyone would be sensible enough to understand that the 'resistor'(whether a single one or a combination) had to have an adequate power rating!

Kind Regards, John

 

[bernardgreen]

The one I made earlier ( 6 years ago ) is not to be found so no photo

Five 22 Ohm resistors in paralllel. effective 4.4 Ohms
12 volt supply on 4.4 Ohms is 2.7 amps , 32 Watts (44 watts @ 14 volts )
Mounted radially on the underside of a finned heatsink with a thermal switch

Heatsink http://www.farnell.com/datasheets/17529.pdf

Resistors http://www.rapidonline.com/Electronic-Components/22R-HS-10W-Arcol-Aluminium-Clad-Resistor-62-8078

thermal cut out from http://www.farnell.com/datasheets/93692.pdf to required temperature

( there are other suppliers )