[Elecraft] QRO - KPA500 Failure

[turnbull]

We should also know the power supply efficiency though as a switcher, I expect 90 plus percent.73 Doug EI2CNSent from my Samsung Galaxy smartphone.
-------- Original message --------From: Andy Durbin <a.durbin at msn.com> Date: 10/02/2020  16:58  (GMT+00:00) To: Doug Turnbull <turnbull at net1.ie>, elecraft at mailman.qth.net Subject: Re: [Elecraft] QRO - KPA500 Failure 

"I understand that efficiency decreases as one derates from
 the maximum of 1500W output.It surprises me that the power dissipated would peak at half power output or 750
 Watts."




I have no test data for the KPA1500 and will not speculate on the shape of the PA dissipation curves.  All I have is data for one KPA500.  For that one KPA500, and under the conditions tested,  it's clear that PA dissipation is greater at half power than at
 full power.




It would be easy to get a pair of data points for the KPA1500.  




Connect the amplifier to a known good 50 ohm load.  

Drive the amplifier to steady state 1500 W output

Record PA current and voltage

Drive the amplifier to steady state 750 W output

Record the PA current and voltage




Repeat on multiple bands if desired and report the results here.




73,

Andy, k3wyc