90E32 Datasheet, PDF (13/71 Pages) Integrated Device Technology – Poly-Phase High-Performance Wide-Span Energy Metering IC

90E32
POLY-PHASE HIGH-PERFORMANCE WIDE-SPAN ENERGY METERING IC
3.4 METERING FUNCTION
The accumulated energy is converted to pulse frequency on the CF
pins and stored in the corresponding energy registers. The 90E32 pro-
vides energy accumulation registers with 0.1 or 0.01 CF resolution.
0.01CF / 0.1CF setting is defined by the 001LSB bit (b9, MMode0).
3.4.1 THEORY OF ENERGY REGISTERS
The energy accumulation runs at 1 MHz clock rate, by accumulating
the power value calculated by the DSP processor.
The power accumulation process is equivalent to digitally integrating
the instantaneous power with a delta-time of about 1us. The accumu-
lated energy is used to calculate the CF pulses and the corresponding
internal energy registers.
The accumulated energy is converted to frequency of the CF pulses.
One CF usually corresponds to 1KWh / MC (MC is Meter Constant, e.g.
3200 imp/kWh), and is usually referenced as an energy unit in this data-
sheet. The internal energy resolution for accumulation and conversion is
0.01 CF.
The 0.01 CF pulse energy constant is referenced as 'PL_constant'.
Within 0.01 CF, forward and reverse energy are counteracted. When
energy exceeds 0.01 pulse, the respective forward/ reverse energy is
increased.
Take the example of active energy, suppose:
T0: Forward energy register is 12.34 pulses and reverse energy reg-
ister is 1.23 pulses.
From t0 to t1: 0.005 forward pulses appeared.
From t1 to t2: 0.004 reverse pulses appeared.
From t2 to t3: 0.005 reverse pulses appeared.
From t3 to t4: 0.007 reverse pulses appeared.
The following table illustrates the process of energy accumulation
process:
Input energy
Bidirectional energy accumulator
Forward 0.01 CF
Reverse 0.01CF
Forward energy register
Reverse energy register
t0
+ 0.005
0.005
0
0
12.34
1.23
t1
-0.004
0.001
0
0
12.34
1.23
t2
-0.005
-0.004
0
0
12.34
1.23
t3
-0.007
-0.001
0
1
12.34
1.23
t4
12.34
1.24
When forward/reverse energy reaches 0.1/0.01 pulse, the respective CFx pins output pulse and the REVP/REVQ bits (b7~0, SysStatus1) are
register is updated. When forward or reverse energy reaches 1 pulse, updated. Refer to Figure-3.
Function Description
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December 9, 2011