Megger INGVAR, Руководство пользователя

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BH0654BE ZP-BH05E 35
7 HOW TO USE INGVAR
7.2 Rules of thumb when
generating current
When you generate current there are rules which can
be useful to follow.
A]
To reduce voltage drop, the current cables
running to the object being tested should
be as short as possible and have sufficient
heavy-gauge (thick) cross-area. You can
reduce the voltage drop further by twisting
cables of different polarity together (see 6.9
"How to arrange the cable sets"), thereby
making it possible to inject higher currents.
B]
If the object being tested has a low imped-
ance connect the Current Unit in parallel.
Connect it in series if the object has high
impedance.
C]
To avoid unnecessary heating of objects be-
ing tested, current can be generated in brief
intervals. It might be best to use manually-
controlled (momentary) injection or time-
limited injection. With INGVAR, it is also
possible to make a coarse adjustment of the
current using the I/30 function (which uses
only 1/30th of the real test current).
D]
When operating time is measured, the value
of the injected current or applied voltage
must exceed the lowest operating limit by
an ample margin (1.2 - 2 times is the rule of
thumb here).
7.3 Setting the desired
current
Low currents
1]
Connect the object being tested to INGVAR
Current Unit output.
2]
Press
TIME
.
3]
Adjust the current using the Current adjust
knob . The value of the current will be pre-
sented on the display.
High currents
High currents can generate a great deal of heat in
both INGVAR and the object being tested. To avoid
unnecessary heating, you can:
A]
Generate current only for brief intervals.
B]
Use the I/30 function .
Generating briefly
There are two easy ways to generate current
for brief intervals:
A]
Using the
MOM
button
B]
Using the limited-time generation function.
These are described in this chapter in section
7.14 “Measuring operating limits”.
Using I/30 function
1]
Connect INGVAR properly to the object being
tested.
2]
Press I/30 button to activate the I/30
function.
3]
Press
TIME
. The current is displayed as
”XXXX/30”. XXXX represents the value the
current will have when the I/30-function is
released.
4]
Adjust the current using the Current adjust
knob . The value of the current will be pre-
sented on the display.
5]
Press OFF button to shut off the current.
6]
Press I/30 button to turn off the I/30
function.
7]
Press
HOLD
to activate the hold function.
8]
Press the
MOM
button briefly.
9]
Read the current presented on the display.
Note The I/30-function is less accurate on none
linear test objects.