power factor meter

[flopy]

Hi....
I need your help in this circuit..
It should give the power factor of the load...
I need to calculate the value of T1 and T2 to test the circuit....
-what is the best available simulation software for such a circuit?

[url]http://www.electro-tech-online.com/electronic-projects-design-ideas-reviews/35047-need-help-circuit.html[/url]

[torbjorn]

Unfortunately, it seems not to be possible to view the schematic without logging in to that other forum, could you please post it at a more open site.

[flopy]

here is the link to circuit....
[url]http://www.4shared.com/dir/3262798/9f2289c0/sharing.html[/url]

[torbjorn]

I would not recommend using transformers at all in a power factor meter, in order to avoid problems due to phase shift, nonlinear phenomena in the core, idle current etc. It would be better to refer all measurement circuitry to the neutral conductor of the line and then, if necessary, make a galvanic separation of DC signals or digital signals by means of optocouplers. Furthermore, it is not a good idea to rely on the insulation of a home-made transformer for electrical safety purposes.

But, anyway, if you still want to use the transformer coupled circuitry, then the best approach to transformer calculations is to first study some textbooks on the subject and then perform the calculations manually. I haven't seen any good general simulation software for the design of transformers, just some spreadsheets that individual design engineers have developed for their own use.

Note that a drawback of your design is that it will be very sensitive to the waveform of the voltage and current. In case of non-sinusoidal waveforms, you would not get a consistent readout. Also, contemplate using a better OP amplifier than the LM324, as that one can have a very high and unstable offset voltage, and furthermore the output suffers from crossover distortion. Take a look at application notes regarding utility energy meters from the leading semiconductor manufacturers, perhaps you can get some design hints there.

[flopy]

thanx ' torbjorn ' for your reply...