App.5-1
IM CW240E
Appendix
App
Appendix 5 Reactive Power
Method
Reactive Power Method
With the CW240, it is possible to select a reactive power calculation method that
either uses the reactive power method (reactive power method 1) or does not
use it (reactive power method 2).
●
When not using the reactive power method (reactive power 2)
The calculation obtains the reactive power through the following formula from
apparent power VA (the product of the rms values of the voltage and current)
and active power P. Even if differing frequency elements are included in the
voltage and current, it is calculated as the rms value.
Even when not using the reactive power method, calculation through the
reactive power method is performed separately, and the polarity (code)
obtained with the reactive power method is used for polarity (SQ).
When the current lags behind the voltage : No polarity display
When the current leads the voltage
: Polarity display is – (minus).
Q = SQ (VA)
2
ÐP
2
Q =
Reactive power
SQ =
Polarity obtained through
the reactive power method
VA =
Apparent power
P =
Active power
In this case, the power factor is also obtained from the apparent power and the
active power, and this power factor is called the rms value power factor. It is an
operation that is used commonly. The polarity obtained with the reactive power
method is used to be able to determine lead/lag of the power factor polarity as
well.