METREL MI 2893 - Current Measurement (Magnitude of Supply Current)

MI 2893 / MI 2892 / MI 2885 Measurement methods
180
All voltage measurements represent RMS values of the voltage magnitude over a 10/12-cycle time
interval. Every interval is contiguous, and not overlapping with adjacent intervals.
L1
L3
L2
N
GND
U1
U2
U3
UN
U12
U23
U31
Figure 149: Phase and Phase-to-phase voltage
Voltage values are measured according to the following equation:
Phase voltage:



M
j
j
pp
u
M
U
1
2
1
[V], p: 1,2,3,N
(1)
Line voltage:



M
j
j
g
j
p
uu
M
Upg
1
2
)(
1
[V], pg.: 12,23,31
(2)
Phase voltage crest factor:
p
pPk
Up
U
U
CF 
, p: 1,2,3,N
(3)
Line voltage crest factor:
pg
pgPk
Upg
U
U
CF 
, pg: 12, 23, 31
(4)
The instrument has internally 3 voltage measurement ranges, which are automatically selected
regarding to the nominal voltage.
5.1.3 Current measurement (magnitude of supply current)
Standard compliance: Class A (Section 5.13)
All current measurements represent RMS values of the samples of current magnitude over a 10/12-cycle
time interval. Each 10/12-cycle interval is contiguous and non-overlapping.
Current values are measured according to the following equation:
Phase current:



M
j
j
pp
I
M
I
1
2
1
[A], p: 1,2,3,N
(5)
Phase current crest factor:
Ip
Ip
Ip
cr
max

, p: 1,2,3, N
(6)
The instrument has internally two current ranges: 10% and 100% range of nominal transducer current.
Additionally, Smart current clamps models offer few measuring ranges, automatic clamp detection and
automatic range selection.