We all learn that a synchronous machine is excited using a DC voltage applied to the field. However, if you look at a static excitation system, the field voltage / current resembles more of a saw-tooth wave form rather than a DC quantity because of the SCR switching.

I'm trying to figure out how the field voltage that is displayed on the operator interface screen is calculated. The manuals don't seem to address this. Seems like it would be a straight RMS calculation, but it appears that the actual calculation is an AC type rms calculation where the DC offset is filtered out. Is this right? If so, why would this be? Why would the DC component be filtered out for the calculation?

Any insight would be greatly appreciated.

nic

 

We generally use the average value for our calculations. I personally use Yokogawa calculator in their software. But from what I have seen the RMS and average values are not very different.