SA9904B Datasheet, PDF (8/12 Pages) List of Unclassifed Manufacturers – Three Phase Power / Energy IC with SPI Interface

SA9904B
sames
POWER CALCULATION
Instantaneous power signals are generated by multiplying the
current and voltage signals, for active power = V x I x Cos(ø) and
for reactive power = V x I x Sin(ø). The power signals are
continuously added to the respective energy registers. Positive
power will be added to the energy register contents and
negative energy will be subtracted.
USING THE REGISTER VALUES
Active and Reactive energy register
The active and reactive energy measured per count can be
calculated by applying the following formulae:
Energy per count = (VRATED x IRATED)/ 320000
(In watt seconds or var seconds)
Where:
VRATED = Rated mains voltage of meter
IRATED = Rated mains current of meter
Mains voltage register
The RMS voltage measurement is accurate to 1% in a range of
50% to 115% of rated mains voltage. The RMS mains voltage
measured by the SA9904B is calculated as follows:
Voltage
=
Where
VRATED
=
VREGISTER VALUE =
VRATED x VREGISTER VALUE / 700
Rated mains voltage of meter
Voltage register value
Mains frequency register
The mains frequency measured by the SA9904B is calculated
as follows:
Frequency = FCRYSTAL / 256 / FREGISTER VALUE
where
FCRYSTAL
=
The external crystal frequency.
FREGISTER VALUE =
Bits D9 to D0 of the frequency
register.
The active and reactive power measured by the SA9904B is
calculated as follows:
Power = VRATED x IRATED x N / INTTIME / 320000
(in Watt or VAR)
Where:
VRATED =
IRATED =
N
=
INTTIME =
Rated mains voltage of meter
Rated mains current of meter
Difference in register values between
successive reads (delta value)
Time difference between successive
register reads (in seconds)
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