How to Plot the Power factor in trend
I need to plot the power factor in trend display. The power factor value range will be -0.5 -0.6....-0.99 1 ..0.9, 0.8,......0.5 . There will not be a zero value. The min value is -0.5 , middle value will be one and max value will be 0.5
If i plot the PF trend, It will come as -0.5 0 +0.5 range.
How can i plot these values correctly?
So your signal range should be -1 to +1.
The trend display gets the max and min ranges from the log configuration aspect for that value.
In turn, the log configuration aspect may try to get range information from the object that holds the power factor value ( or whatever value you are logging) depending on what type of object is used to store and display the power factor.
E.g. a SignalReal object uses the min and max range of realIO.parameters
Check the ranges in your power factor object and the log configuration aspect. You can override the range settings in the log configuration aspect if required.
You can create the following simple code in the PLC:
if PF<0 then
In this case PF_calc will vary from -0.5 ... 0 ... 0.5 which will correspond to PF -0.5 to 0.5 trough 1 and you can plot trend for PF_calc
In this case you need to create custom scale for your trend with the real values for the range of PF: from -0.5 ... 1... 0.5 (middle is 1 instead of 0) or leave the trend without scale. The problem could be a ruller, which will show incorrect value ! But if you need the trend only for visual presentation, it is OK.
Here both PF=-1 and PF=1 will give 0 (which is true from phisycal point of view = only active power)
I'm using this technique for realizing of PF controller in my logic, where I faced the same problem.