VT Error

[Cerkit]

Hi,

Does anyone know how I can calculate the Voltage Error and Phase error for a VT at a given output voltage if I know the error for other output voltages?

So in this instance a single phase VT has voltage error +0.8%,phase error 15minutes at output of 20VA with unity power factor. For an output of 110VA unity power factor the voltage error is -0.1%, phase error -3 minutes.

How can I calculate the the voltage and phase error at an output of 150VA unity power factor?

Thanks

 

[scottf]

You said "output voltages", but it sounds like you want to calculate the accuracy at a different burden (power output).

The accuracy of a VT (at a given voltage) moves linearly/proportionately with changes in burden (VA).

So you can plot the 2 points that you know and then extend the load line to 150VA.

This bulletin talks a bit about this. The ratings are in IEEE-speak, but the concept is the same.

http://www.ritzusa.com/resources/43.pdf

 

[Cerkit]

Hi,

So if I plot two graphs, one Verror vs Burden and another Phase error vs Burden I can extrapolate, is this correct?

Thanks

 

[scottf]

No, please see the link I posted above. The graph is phase angle error and ratio error plotted at various burdens.