STPM01 datasheet(45/60 Pages) STMICROELECTRONICS

Part #	STPM01

Description	Programmable single phase energy metering IC with tamper detection

PDF	60 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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45 / 60 page

STPM01

Theory of operation

Doc ID 10853 Rev 8

45/60

Equation 3

i(t) = I • sin (

ωt + ϕ);

where I is the peak current,

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

between voltage and current.

8.24.1

Active power

In the STPM01, 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

differentiated stage which transforms:

Equation 4

v(t)

→ v’(t) = dv/dt = V

⋅ ω ⋅ cos ωt − [see Figure 28 - 5]

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

Equation 5

i(t) = I

⋅ sin(ωt + ϕ); [see Figure 28 - 6]

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

two additional stages which perform the integration of themselves, obtaining:

Figure 28.

Active energy computation diagram

STPM01 Datasheet(PDF) 45 Page - STMicroelectronics