STPM01FTR datasheet(43/56 Pages) STMICROELECTRONICS

Part #	STPM01FTR

Description	Programmable single phase energy metering IC

PDF	56 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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43 / 56 page

STPM01

Theory of operation

43/56

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:

v(t)

→v’(t) = dv/dt = V

⋅ ω⋅ cos ωt −[Eq. 2 - see (5)]

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

i(t) = I

⋅ sin(ωt + ϕ); [Eq. 3 - see (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:

dv/dt

→ v(t) = V

⋅ sin ωt; [Eq. 4 - see (7)]

i(t)

→

[Eq. 5 - see (8)]

Now four signals are available. Combining (pairing) them by means of two multiplying stages

two results are obtained:

Figure 27.

Active energy computation diagram

)

cos(

)

(

)

(

⋅

−

⋅

∫

STPM01FTR Datasheet(PDF) 43 Page - STMicroelectronics