Not sure why that's a surprise. It's a linear amp ... the bias point is
what draws the current, and therefore essentially determines the
dissipation. There's nothing remarkable about it.
Amplifier 101.
Dave AB7E
On 8/16/2018 10:17 PM, char...@k5ua.com wrote:
Thanks for the replies.
Upon further testing, I have found that the efficiency of the KPA-1500
is varies greatly with driving power. The following table illustrates
the relationships between exciter power, voltage, current,
power-in(voltage x amps), power-out, efficiency, and dissipated power.
The following test was made with the KPA-1500 into a dummy load and
readings from the KPA-1500 utility software.
(Exciter)(Amps) (Voltage) (Power-In) (Power-Out) (Efficiency Pout/Pin)
(Dissipated Pwr)
10w 29a 52.7v 1528w 375W 375/1528 =
24.5% 1205w
15w 37a 52.7v 1950w 620w 620/1950 =
31.7% 1335w
20w 43a 52.6v 2262w 861w 861/2262 =
38.0% 1413w
25w 47a 52.6v 2472w 1060w 1060/2472 =
42.8% 1451w
30w 51a 52.6v 2682w 1227w 1227/2682 =
45.7% 1420w
35w 53a 52.5v 2782w 1380w 1380/2782 =
49.5% 1412w
40w 55a 52.5v 2887w 1497w 1497/2887 =
51.9% 1382w
45w 56a 52.5v 2940w 1600w 1600/2940 =
54.4% 1313w
50w 57a 52.5v 2992w 1703w 1703/2992 =
56.9% 1315w
53w 59a 52.5v 3097w 1825w 1825/3097 =
58.9% 1306w
The remarkable thing is that DISSIPATED POWER appears to be relatively
constant from 375w output through 1825w output. This implies the
KPA-1500 will need to dissipate nearly the same amount of heat at low
power output as at high power output, if I am interpreting the data
correctly. I would like to know from Elecraft if this is normal behavior.
Charles K5UA
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