ac current source

[m3]

Hello everyone,

I need an AC senoidal (60Hz)voltage controlled current souce, capable to generate 20 Amps @ 2Vrms and no load impedance dependece. My goal is to build the KWH meter tester.

Best Regards,

m3

 

[BrianG]

How about using a high-power audio amplifier. The output impedance can be very low but you might need an impednace matching transformer to get the 20A current without stressing the output stage too much. To complete the design you need to sense the load current to get negative feedback to balance any load variation. This can be done with a simple op-amp resistive summing circuit. The 60Hz source input connects to the other summing input and is varied by a voltage controlled attenuator chip to set the required test current.

 

[turbo22]

One possibility is to use a CT (current transformer) in reverse. Assuming a 1000:1 turns ratio, you could apply 20 mA to the input side and extract 20 Amps from the output. (You might watch your impedance transformation for problems). Building a 20 mA current source would involve a simple voltage to current converter using a decent opamp and driving the input from your function generator. The trick is selecting the correct CT.

 

[BrianG]

turb022 - I don't think that will work with an op-amp. I make it that the sort of maximum power required is 40W (i.e. 20A x 2V), hardly op-amp territory!

 

[nbucska]

If the frequency dependency is guaranted by design, use
a transformer at 60Hz with two taps or series resistor
in the primary.

<nbucska@pcperipherals.com>