Datasheet

STPMC1 Theory of operation
Doc ID 15728 Rev 7 45/77
An asymmetrical compensation is implemented by multiplying the phase current with α and
the neutral current with β and these values are subtracted from neutral and phase currents
respectively, as shown below:
i
CS
= β i
T
i
CT
= α i
S
For other values of SYS, the values of CCA and CCB three correction factors, a 7-bit α, 6-bit
β and 4-bit γ (gamma) are calculated as follows:
Equation 7
Equation 8
Equation 9
From these factors a 4 x 4 matrix, shown in
Ta bl e 3 0 , implements a symmetrical
compensation multiplying each phase and neutral current with its row, adding the products
together and subtracting them from the currents.
i
CR
= α i
S
+ β i
T
+ γ i
N
i
CS
= α i
R
+ α i
T
+ β i
N
Table 29. Mutual current compensation matrix for single-phase systems (SYS > 3)
phase S T
S-β
T α -
( ± 0.78 %)
()
[]
[]
8192
0:5CCA1
8CCA
⋅−
=α
( ± 0.39 %)
()
[]
[]
8192
3:7CCB1
7CCA
⋅−
=β
( ± 0.09 %)
()
[]
[]
8192
0:2CCB1
6CCA
⋅−
=γ
Table 30. Mutual current compensation matrix for three-phase systems (SYS < 4)
phase R S T N
R - αβγ
S α - αβ
T βα- α
N γβα-