STPM32TR datasheet(59/121 Pages) STMICROELECTRONICS

59 / 121 page

DS10272 Rev 8

59/121

STPM32, STPM33, STPM34

Theory of operation

121

To calculate the filtering time for the sag event, we consider the time in which the nominal

instantaneous voltage is below the sag threshold, that is:

Equation 15

To correctly distinguish between normal sinusoidal voltage and sag event, the filtering time

should be added to this component, for example half line period (10 ms at 50 Hz). Since

LSB of SAG_TIME_THRx register is 8

s (FCLK = 125 kHz), the value to set is:

Equation 16

In the same way:

VSWELL: target RMS value of swell voltage

AV: voltage sensor gain

DSWELL = 210, length of swell threshold register

calV = 0.875, calibrator mid value

Following the above calculation we obtain the hexadecimal value of voltage swell threshold:

Table 17. Voltage swell

Parameter

Value

Table 16. Voltage sag (continued)

Parameter

Value

SAG

VSAG

Vref

-------------- AV

2calV

R1 R2

--------------------





DSAG HEX





LSBSAG

R1 R2

 V

ref



2R2 calV D



SAG





------------------------------------------------------------------ V



time

2 arc

VSAG

--------------





sin

1000

f

------------- ms





SWELLV

VSWELL

Vref

--------------------- AV

R1 R2

-------------------- calV D



SWELL HEX







LSBSWELL

Vref R1 R2





2R2 calV D



SWELL





------------------------------------------------------------------------- V



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