http://elecraft.85.s1.nabble.com/Wattage-Draw-K3S-100-vs-KPA500-KAT500-for-UPS-tp7633842p7633850.html
I did not consider the efficiency of the power supply. The 600W was the difference between his shack load with the receiver in standby and in full transmit. So as you state, if the power supply is only 50% efficient, then 276W times 2 would be close to the 600W difference.
> On Aug 30, 2017, at 7:33 AM, Bob McGraw K4TAX <
[hidden email]> wrote:
>
> Tom, Bret et al;
>
> I agree with you ........... something is not right. I see my K3S draws about 1.2 amps DC on receive. at 1.38 volts that's about 17 watts. If my supply is only 50% efficient, that's 35 watts. I can't understand where the 350 watts would be used unless other equipment is being used. And I agree that transmit is 20 amps at 13.8 volts or 276 watts. Again with a supply that is 50% efficient, that is only 550 watts or so. Certainly no where near the "over 900 W".
>
> Perhaps the computer, monitor, lamp, printer and other ancillary equipment is part of the load on the UPS. It is more likely the inductive load on the UPS is creating an issue with the power output indication. Although that doesn't explain the UPS shut down or fold back in power. One other issue regarding the UPS, is the output Pure Sine Wave, Modified Sine Wave or Square Wave? This may have a significant impact on its function with various types of loads.
>
> One way to evaluate the indication of the UPS output is to use an incandescent bulb of 150 to 300 watts. They are resistive and reasonably accurate with regard to power consumption. Don't use any of the bulbs which are "equivalent" rated ones. I use this method as a load when I've had to repair any of my DC to AC inverters.
>
> 73
> Bob, K4TAX
>
>
> On 8/30/2017 6:50 AM, KQ5S-Tom wrote:
>> Something is not right. If your UPS is showing 350 with the K3S at idle and over 900 on transmit that is a difference of close to 600. The K3S draws 17-22 amps at full key down and 100 watts. Assume 20 amps at 13.8V. That is only 276. You are showing double that.
>>
>> ---------
>> KQ5S-Tom
>>
>>
>>
>>
>>> On Aug 30, 2017, at 6:16 AM, MaverickNH <
[hidden email]> wrote:
>>>
>>> As mentioned in another thread, I'm running my shack on a UPS that is rated
>>> 1500va/900w. With my K3S/100 and other hardware plugged in on the same input
>>> the UPS often max's out at 900W at < 100W on the K3S. Typically, the
>>> baseline with K3S on RX is ~350W and it spikes over 900W with TX at 100W and
>>> the UPS limits output. So it seems 100W isn't 100W.
>>>
>>> I'm looking to switch in another UPS rated 2200VA/1320W, or 420W higher, for
>>> use with the KPA500/KAT500 I just acquired from another forum member. so
>>> from a 100W station to a 500W station. Might this work or is the increase in
>>> watt TX not equal to the watt drawn?
>>>
>>> BRET/N4SRN
>>>
>>>
>>>
>>> --
>
>
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