Re: OLTC primary loss measurement

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>



>
> I have a friend who has worked professionally assessing heatsink
efficiency
> and modest setup or environmental changes do lead to significant changes
in
> degC/watt for a given sink.
> But in controlled environments ie stll air and limited room gradients good
> repeatability is possible in his experience.

Exactly..the sink temperature/watt relation is generally pretty repeatable
(even in normal lab environment with the a/c blowing), which is why the DC
replacement technique should work pretty well (at least to 5%, probably
better) (hey, if it works for RF measurements in a precision power meter, it
can work here, right?)


>
> A simple method (short of full calorimetric measurements) to get more
> accurate results might be to run pure DC thru the IGBT array and to
> calibrate the degrees centigrade per watt figure for the system. This
could
> be done at about the same power loss level expected for the operating
tesla.