10-10
IM 253710-01E
• Delta>Star
Using the data from a three-phase, three-wire system or a three-voltage, three-current
system, the various data of a star connection are computed from the data of a delta
connection (delta-star transformation).
∆
U1(
∆
Urms1,
∆
Umn1,
∆
Udc1,
∆
Uac1)
∆
U2(
∆
Urms2,
∆
Umn2,
∆
Udc2,
∆
Uac2)
∆
U3(
∆
Urms3,
∆
Umn3,
∆
Udc3,
∆
Uac3)
∆
I4(
∆
Irms4,
∆
Imn4,
∆
Idc4,
∆
Iac4)
±
I
R
S
T
±
U
±
U
±
I
N
I1
I2
U2
U1
∆
U1
∆
U3
∆
U2
∆
I4
±
I
±
I
R
S
T
±
U
±
U
±
U
±
I
N
I1
I2
I3
U3
U2
U1
∆
U1
∆
U3
∆
U2
∆
I4
• Star>Delta
Using the data from a three-phase, four-wire system, the various data of a delta
connection are computed from the data of a star connection (start-delta
transformation).
∆
U1(
∆
Urms1,
∆
Umn1,
∆
Udc1,
∆
Uac1)
∆
U2(
∆
Urms2,
∆
Umn2,
∆
Udc2,
∆
Uac2)
∆
U3(
∆
Urms3,
∆
Umn3,
∆
Udc3,
∆
Uac3)
∆
I4(
∆
Irms4,
∆
Imn4,
∆
Idc4,
∆
Iac4)
±
I
±
I
R
S
T
±
U
U
±
U
±
I
N
±
I1
I2
I3
U1
U2
U3
∆
U1
∆
U3
∆
U2
∆
I4
Note
•
If the sampled data used in the computation do not exist (for example, when the module is not
installed), the sampled data are considered to be 0’s for the computation.
•
It is recommended that the measurement range and scaling (PT/CT ratio and coefficients) of
the elements that are being computed (delta computation) be set the same as much as
possible. Using a different measurement range or scaling causes the measurement
resolution of the sampled data to be different. In effect, the computation result will have
errors.
•
The type of delta computation can be selected when the data acquisition is stopped and the
various data can be recomputed. For details, see section 10.1.
•
The number that is attached to the measurement function symbol of the delta computation
has no relation to the element number. For example, if [i1-i2] is selected from the delta
computation menu, the true rms value of [i1-i2] is computed and displayed at [
∆
Irms1].
•
When the measurement/computation period is changed, do a re-computation. For details,
see section 10.1.
10.2 Selecting the Delta Computation