Testboy TV 455 - Page 48

®
TV 450/455 Line impedance
48
Step 2: Measuring the voltage drop
 Select the ΔU sub-function using the function selector switch and / keys.
 Select test parameters (Fuse type must be selected).
 Connect test cable or plug commander to the instrument.
 Connect the test leads to the tested points (see figure 5.30).
 Press the TEST key to perform the measurement.
 Store the result by pressing the MEM key.
* model MI 3125B
Step 1 - Zref Step 2 - Voltage drop
Figure 5.31: Examples of voltage drop measurement result
Displayed results:
ΔU ...........Voltage drop,
ISC............Prospective short-circuit current,
Z..............Line impedance at measured point,
Zref..........Reference impedance
Voltage drop is calculated as follows:
[]
100
)(
% ⋅
⋅−
=Δ
N
NREF
U
IZZ
U
where:
ΔU........ calculated voltage drop
Z………impedance at test point
Z
REF
…...impedance at reference point
I
N
………rated current of selected fuse
U
N
…….nominal voltage (see table below)
U
n
Input voltage range (L-N or L1-L2)
110 V
(93 V ≤ U
L-PE
< 134 V)
230 V
(185 V ≤ U
L-PE
≤ 266 V)
400 V
(321 V < U
L-N
≤ 485 V)
Note:
 If the reference impedance is not set the value of Z
REF
is considered as 0.00 Ω.
 The Z
REF
is cleared (set to 0.00 Ω) if pressing CAL key while instrument is not
connected to a voltage source.
 I
SC
is calculated as described in chapter 5.6.1 Line impedance and prospective
short circuit current.