STPM10 datasheet(37/51 Pages) STMICROELECTRONICS

No de pièce	STPM10

Description	Programmable single-phase energy metering IC with tamper detection

PDF	51 Pages

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Fabricant	STMICROELECTRONICS [STMicroelectronics]

Site Internet	http://www.st.com

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37 / 51 page

STPM10

Theory of operation

Doc ID 17728 Rev 3

37/51

where I is the peak current,

ω is related to the line frequency and ϕ is the phase difference

between voltage and current.

7.23.1

Active power

In the STPM10, after the pre-conditioning and the A/D conversion, the digital voltage signal

(which is dynamically more stable with respect to the current signal) is processed by a

differentiator stage which transforms:

Equation 7

v(t)

→ v’(t) = dv/dt = V

⋅ ω ⋅ cos ωt − [see Figure 26 - 5]

the resulting signal, together with the pre-processed and digitalized current signal:

Equation 8

i(t) = I

⋅ sin(ωt + ϕ); [see Figure 26 - 6]

are then available for the calculation process. These digital signals are also provided to two

additional stages, which then integrate of themselves, obtaining:

Equation 9

dv/dt

→ v(t) = V

⋅sin ωt; [see Figure 26 - 7]

Equation 10

i(t)

→

[see Figure 26 - 8]

)

cos(

)

(

)

(

⋅

−

⋅

∫

STPM10 Fiches technique(PDF) 37 Page - STMicroelectronics