STPM01_11 STMICROELECTRONICS [STMicroelectronics], STPM01_11 Datasheet - Page 48

• Manufacturer Part Number: STPM01_11
• Description: Programmable single phase energy metering IC with tamper detection
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Theory of operation
8.24.3
48/60
Equation 16
The reactive power will present then a ripple at twice the line frequency. Since the average
value of a sinusoid is 0, this ripple does not contribute to the reactive energy calculation over
time, moreover, in the STPM01 the reactive power is not used for meter calibration or to
generate the stepper pulses, then this ripple will not affect the overall system performances.
In case of Rogowsky coil, the same procedure is applied, but the current channel will be
proportional to the derived of the current and the differentiated is bypassed in the voltage
channel, so we have:
Equation 17
Equation 18
The reactive power is then calculated:
Equation 19
Apparent power and RMS values
The RMS values are calculated starting from the following formulas.
Shunt or current transformer
Equation 20
multiplying
Q
Q
Q
Q
1
3
1
3
T
1
) t (
) t (
) t (
) t (
∫
T
0
=
=
=
=
I
2
∫
v
(
2
2
1
1
v
) t (
) t
) t (
⋅
⋅
Equation 20
dt
Q
Q
dt
′ ⋅
i
1
1
) t (
) t (
) t (
⋅
=
∫
⋅
i
⋅
ω
=
′
ω
) t (
ω
V
⋅
=
dt
=
I
sin
VI
VI
2
=
2
2
by
V
ω
⋅
) t (
⋅
ω
(
(
t
sin
sin
) t (
, the I
⋅
i
Doc ID 10853 Rev 8
) t (
⋅
ϕ
ϕ
(
=
−
−
+
RMS
⎛
⎜
⎝
I
sin(
sin(
ω
−
cos(
V
ω
value is obtained:
2
2
cos(
ω
ω
t
ω
t
+
+
t
ω
ϕ
+
ϕ
) t
)
)
ϕ
)
⎞
⋅ ⎟
⎠
)
)
(
)
−
=
I
sin(
−
VI
2
ω
t
⋅
ω
+
ϕ
⋅
)
(
sin
)
=
2
ϕ
VI
ω
−
(
sin
sin(
ϕ
2
+
ω
sin(
t
+
2
ϕ
STPM01
ω
)
)
t
+
ϕ
)
)