Electrex X3M, Руководство пользователя

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8.2.2 Measurement Formulas:
Phase-phase Voltages:
31 23 12
, , U U U
( )
∑
−
=
=
1
0
2
12 12
1
M
n
n U
M
U
;
( )
∑
−
=
=
1
0
2
23 23
1
M
n
n U
M
U
;
( )
∑
−
=
=
1
0
2
31 31
1
M
n
n U
M
U
( ) ( ) ( )
n U n U n U
31 23 12
, ,
are the Phase to phase Voltages samples.
M is the number of samples taken over a period (64)
Phase to phase Voltages THD
12
U
THD
,
23
U
THD
,
31
U
THD
in %
1
2
sin ) (
2
cos ) (
2
) (
100
2
1
0
12
2
1
0
12
1
0
2
12
12
−
⎪⎭
⎪
⎬
⎫
⎪⎩
⎪
⎨
⎧
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
+
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
=
∑ ∑
∑
−
=
−
=
−
=
N
n
N
n
N
n
U
N
n
n U
N
n
n U
N
n U
THD
π π
1
2
sin ) (
2
cos ) (
2
) (
100
2
1
0
23
2
1
0
23
1
0
2
23
23
−
⎪⎭
⎪
⎬
⎫
⎪⎩
⎪
⎨
⎧
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
+
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
=
∑ ∑
∑
−
=
−
=
−
=
N
n
N
n
N
n
U
N
n
n U
N
n
n U
N
n U
THD
π π
1
2
sin ) (
2
cos ) (
2
) (
100
2
1
0
31
2
1
0
31
1
0
2
31
31
−
⎪⎭
⎪
⎬
⎫
⎪⎩
⎪
⎨
⎧
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
+
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
=
∑ ∑
∑
−
=
−
=
−
=
N
n
N
n
N
n
U
N
n
n U
N
n
n U
N
n U
THD
π π
Phase Current:
3 2 1
, , I I I
( )
∑
−
=
=
1
0
2
1 1
1
M
n
n I
M
I
;
( )
∑
−
=
=
1
0
2
2 2
1
M
n
n I
M
I
;
( )
∑
−
=
=
1
0
2
3 3
1
M
n
n I
M
I
( ) ( ) ( )
n I n I n I
3 2 1
, ,
are the line current samples.
Phase Current THD:
1
I
THD
,
2
I
THD
,
3
I
THD
1
2
sin ) (
2
cos ) (
2
) (
100
2
1
0
1
2
1
0
1
1
0
2
1
1
−
⎪⎭
⎪
⎬
⎫
⎪⎩
⎪
⎨
⎧
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
+
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
=
∑ ∑
∑
−
=
−
=
−
=
N
n
N
n
N
n
I
N
n
n I
N
n
n I
N
n I
THD
π π
1
2
sin ) (
2
cos ) (
2
) (
100
2
1
0
2
2
1
0
2
1
0
2
2
2
−
⎪⎭
⎪
⎬
⎫
⎪⎩
⎪
⎨
⎧
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
+
⎥
⎦
⎤
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
=
∑ ∑
∑
−
=
−
=
−
=
N
n
N
n
N
n
I
N
n
n I
N
n
n I
N
n I
THD
π π