STPMC1 ST Microelectronics, STPMC1 Datasheet - Page 69

• Manufacturer Part Number: STPMC1
• Description: Programmable poly-phase energy calculator IC
• Manufacturer: ST Microelectronics

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STPMC1
10.3
10.4
Voltage and current RMS values calculation
The I
Equation 48
The Ui
Equation 49
In case of non Rogowski sensor, the same dedicated RMS blocks produce some other
values, because input values for the blocks are changed.
Therefore, another RMS value, named Ii
Equation 50
The U
Equation 51
Energy integration
The internal hard-wired DSP unit performs all the computations above in real time for a
power line in parallel by means of arithmetic blocks. Due to implementation of an integrator,
up/down counter or deviator, part of which is also an integrator in a feedback, additional
factors are introduced into computations. If we declare f
frequency and M as number of possible values of some integrator, the following constant
factors can be defined:
I
Ui
Ii
U
RMS
RMS
RMS
RMS
k
k
RMS
k
L
k
S
RMS
k
D
RMS
k
D
INT
INT
=
=
value is produced from 16-bit value of
=
is produced from stream and 16-bit value of
=
is produced from stream and 16-bit value of
T
1
T
1
T
∫
0
T
1
T
∫
0
T
1
v
v
T
∫
0
∫
T
0
2
di
v
ui
2
v
dt
dt
2
ii
2
si
dt
dt
= A
= Ak
= B
= C/
INT
2
1
1
2
/
Doc ID 15728 Rev 1
2
1
1
2
RMS
is produced from 16-bit value of
Equation 15
Equation 23
MCLK
Equation 14
:
Energy calculation algorithm
as the measurement clock
:
:
Equation 24
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: