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4 - Front Panel Operation
52
7 - Measuring Peak Inrush Current
Peak inrush current is a non-repetitive measurement in the sense that peak inrush current occurs only
when the unit under test is first turned on. In order to repeat the measurement, you must turn the unit off
and wait for any input filter capacitors to discharge completely.
This example shows you how you can measure the peak inrush current using the front panel meter. The
voltage is set to 120 V rms and the output is triggered at an output phase of 75°, which optimizes the
conditions under which inrush current is applied to the unit under test.
Action Display
1.
Set the immediate voltage to 0. Press Voltage, then press 0 and Enter.
VOLT 0
2. Set the triggered voltage to 120 V rms. In the Voltage menu, press ô to
access the triggered voltage command. Then press 1 2 0 Enter.
VOLT:T 120
3. Set the voltage mode to step. In the Voltage menu, press ô to access the
mode command. Press ° to scroll to STEP and press Enter.
VOLT:M STEP
4. Make sure the unit is operating in the low voltage range. (The low voltage
range has twice the output current rating of the high voltage range.) In the
Voltage menu, press ô to access the range command. If necessary, press ° to
set the range to 150 and press Enter.
RANGE 150
5. Make sure the triggered voltage slew rate is set to the fastest possible speed.
In the Voltage menu, access the triggered slew command. If necessary, reset
the slew rate to a faster speed.
SLEW:T 9.9000+E37
6. Make sure the peak current and rms current limits are set to high values. In the
Current menu, access the rms current limit and then the peak current limit
commands. If necessary, reset the rms current and the peak current limits to
higher values.
(Agilent 6811B units have an rms current limit of 3.25 A. Agilent 6813B units
have an rms current limit of 13 A and a peak current limit of 80 A)
CURR:LEV 6.5
CURR:PEAK 40
7. Synchronize the trigger source with a reference phase angle. In the Trigger
Control menu, press ô to access the sync source command. Press ° to obtain
PHASE and press Enter.
SYNC:SOUR PHASE
8.
Set the reference phase angle to 75
°
. In the Trigger Control menu, press ô to
access the sync phase command. Then press 7 5 Enter.
SYNC:PHAS 75
9. Initiate (or enable) the unit for one immediate trigger from the front panel.
Press Trigger Control and Enter.
INIT:IMMED
10. Set the meter function to measure nonrepetitive peak inrush current. In the
Meter menu, press ô to access the peak inrush current display.
0 A PK NR
11. Enable the output by pressing Output On/Off. 0 V 60 HZ
12.
Send the trigger to step the output from 0 V to 120 V. Press Shift Trigger.
The inrush current is displayed on the Meter.
48 A PK NR
On three-phase ac sources you can only return the peak inrush current from the selected phase because
the front panel can only display one phase at a time. Refer to the ac source Programming Guide on how
to return simultaneous measurements from all three phases.