How does this Tester output more power than input power?

[arnoudvh]

We recently had our AC power metering unit tested at a test lab which uses a RadianResearch WECO model 2350, which has been updated to WECO 4050X, 4150X and 4330X according to their website.

These units can output and measure voltages upto 600V AC and upto 330A (for 4330X model). I can confirm our test unit was actually subjected to 240V AC and "only" 20A - but that is still 4800 Watt.

However, the whole test system is powered from a measly 120V plug with max 1500 W power draw. I looked at their patents - I get that you can run a very high current using a transformer at very low voltage - but it seems this system is running at actual high voltage AND high current (way more than the input power).

How can they produce upto 198 kilowatts from a 120V/1500W socket?? Does anybody understand what wizardry is going on??

[Kleinstein]

For testing the power meter the test current does not really have to flow at the same voltage that the voltage sense input of the power meter sees.
The 20 A or more test current would only flow with a much lower voltage of maybe some 1-5 V, just to overcome the burden of the power meter, cables and shunt or current transformer.
So the power needs would be more like 20 A x 3 V and a few mA at the high voltage. So more in the 60 W range.

[SeanB]

Yes they use a few transformers, and separate the voltage from the current measurement, by having one transformer, normally a variac driving a regular 1:2 isolation transformer, to get the 230V range capability, with this connected to the input line and neutral, allowing you to drive the line voltage coils, or the internal power supply for electronic ones. Then you have a separate variac, driving another transformer, this one being120VAC to around 12VAC, but with a secondary capable of providing 100A of current. This then is connected between the line input and the line output, with an ammeter connected in series as well. Line voltage and line current are then set to the correct values, and they run the unit with a set current and voltage for a few hours, checking for the analogue units that the faraday disk does the correct number of turns per unit, or the digital one shows the correct number of pulses.

[arnoudvh]

Thanks, got it - that all makes sense now!

PS: impressed how active this forum is! Fast answers!