STPMC1 datasheet(30/77 Pages) STMICROELECTRONICS

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Theory of operation

STPMC1

30/77

Doc ID 15728 Rev 6

The value IMAX corresponds to the maximum current value hold by each RMS current

current channel gain. Let us suppose that

IMAX = 180 A

The tamper condition is evaluated only if

This means that the sum of the RMS value of currents is not negligible with respect to

IMAX (the threshold corresponds to about 0.4% of IMAX).

In this case this is true since:

IR + IS +IT +IN = 14.4 A > 0,703125 A = IMAX / 256

The criterion for tamper detection is

This can also be expressed as

which means the sIRMS value must not exceed 3.13% of (IR + IS +IT +IN).

In this example:

sIRMS = 0,149967 < 0.45 = (IR + IS +IT +IN) / 32

Then BCS = 0.

Figure 11.

Currents of the three phase system in example

∑

256

MAX

()

RMS

∑

()

sIRMS

RMS

∑

⎟

⎠

⎞

⎜

⎝

⎛

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