MI 2892 Power Master
Theory and internal operation
150
Phase voltage:
M
j
j
p
p
u
M
U
1
2
1
[V], p: 1,2,3,N
(1)
Line voltage:
M
j
j
g
j
p
u
u
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
p
p
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 and automatic detection.
5.1.4
Frequency measurement
Standard compliance: IEC 61000-4-30 Class A (Section 5.1)
During RECORDING with aggregation time Interval:
≥
10 sec frequency reading is obtained every 10 s.
The fundamental frequency output is the ratio of the number of integral cycles counted during the 10 s
time clock interval, divided by the cumulative duration of the integer cycles. Harmonics and
interharmonics are attenuated with digital filter in order to minimize the effects of multiple zero
crossings.
The measurement time intervals are non-overlapping. Individual cycles that overlap the 10 s time clock
are discarded. Each 10 s interval begin on an absolute 10 s time clock, with uncertainty as specified in
section 6.2.19.
For RECORDING with aggregation time Interval:
<
10 sec and on-line measurements, frequency reading
is obtained from 10/12 cycles frequency. The frequency is ratio of 10/12 cycles, divided by the duration
of the integer cycles.
