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>

Or, because you probably don't know all the thermal resistances and masses 
involved, do a replacement energy approach...   Run the coil, measure the 
temperature rise at some convenient place.

Then, arrange to have the parts dissipate DC power (which is easy to 
measure as I * V) to match the temperature rise.  Something as simple as a 
variable voltage source to bias the devices partly on, with a DC source 
(like a big battery) across the "switch" terminals (C to E, I imagine)... 
You don't care about the losses in the battery or wire, because you can 
measure the current anywhere in the loop (Kirchoff's current law helps 
here...) and use a Hi-Z volt meter to measure the voltage drop across the 
devices (at whatever convenient boundary you want to use).



At 09:12 AM 8/30/2002 -0600, you wrote:
>Original poster: "tesla by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><tesla-at-paradise-dot-net.nz>
>
>Greetings Terry et al
>
>I wonder if it's practical to actually measure the IGBT lossses directly
>1) Operate coil in still air environment
>2) Run near full power until in thermal equilibrium
>3) Do the sums for the heatsink thermal d(temperature) from its published
>thermal resistance to air.
>4) Thus directly derive power driving the thermal rise.
>5) Compare with power I/P and volia
>Best
>Ted L in NZ