METREL Euro Z 440 V, Инструкция по эксплуатации

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MI 3143 Euro Z 440 V Test and Measurements
20
where:
Z ........................................ Impedance
U
UNLOADED
............................ Measured voltage [no load]
U
LOADED
............................... Measured voltage [with load]
ΔU ...................................... Voltage dip
I
test
...................................... Test current
6.1.3 High Current Measurement
The measurement can be applied for measuring contact resistance (bad contacts) in a live
distribution board or fuse box. With test currents from 10 A and all the way to the 100 A,
depending on the mains voltage and test load parameter. For more information, see chapter
9.4
Test Current.
C1
P1
P2
C2
MI 3143 Euro Z 440 V
E a r t h
L1
L2
L3
N
Pe
R1
4 wire (Kelvin)
V
A
S
up
ply
R4
R
Itest
U
R1
R3 R2
Itest
U
AC
U
R1+R2
U
R1+R2+R3
Figure 6.4: High Current Measurement example (distribution board)
During the measurement, an internal resistance is connected between C1 and C2 for a period of
a half cycle. The current is measured by the Euro Z instrument (I
test
). The supply network and
test load setting determines the current amplitude. A higher current amplitude improves the
immunity against voltage noise. Potential probes P1 and P2 measure the voltage dip. The
resistance R is determined from the voltage / current ratio.
In the example, following resistance is measured:
𝛥𝑅 =
𝑈
𝑃1−𝑃2
𝐼
𝑡𝑒𝑠𝑡
where:
ΔR ...................................... Resistance
U
P1-P2
.................................. Voltage dip [with load]
I
test
...................................... Test current
[V]
[s]
[V]
[s]
U
P1-P2
[A]
Itest
U
C1-C2
Figure 6.5: High Current measurement voltage and current waveforms examples