6.3 Motors
You can measure starting (inrush) current, running current,
and current imba
l
ance. Inrush current is typically 6 times
the value of running current, depending on the motor type.
1. Press the ON OFF pushbutton to turn on this Meter.
2. Clamp around a motor phase condu
c
tor. Be sure the
clamp jaws are securely closed, or measurements will
not be accurate.
3. While wat
c
hing the bar graph, turn on the motor and
observe the level of inrush current. In this case, the bar
graph is better than the digital display because the bar
graph response is faster than the digital display.
4. When the motor reaches the desired speed, observe
the running current.
5. Repeat your measurement for each motor phases.
Unbalanced
c
urrent may be caused by a voltage
imbalance, or a shorted motor winding.
6. Repeat steps 1 thru 3, then press the MIN MAX
pushbutton to enable RECORD.
2524
7. Turn on the motor. When the motor gets to the desired
speed, note the blinking upper bar on the bar graph
(inru
s
h rms current), and the d
i
s
played level (running
rms current).
8. To view the maximum inrush current, press the MIN
MAX pushbutton once.
9. Repeat step 6, if necessary.
10. To clear RECORD, press the MIN MAX pushbutton for
2 seconds.
6.4 Distribution Transformers
You can measure excessive current, load balance between
phases, true-rms and frequency of neutral current. True-
rms measurement yields the effective value.
1. Press the ON OFF pushbutton to turn on this Meter.
2. Clamp around a phase wire of the transformer. Be sure
the clamp jaws are securely closed, of measurements
will not be accurate.
3. Observe the display for true-rms current flow.
4. Repeat your measurement for each phase to observe
balance. Unbalanced phases cause large neutral
currents flow.
5. Clamp around the neutral wire.
6. Observe the display for true-rms current flow. Any
significant flow, with balanced phases, indicate
s
the
presence of harmonic currents.
7. Press the Hz pushbutton to measure the frequency of
neutral wire. Reading indicates the frequency of the
dominant current flow (in case of harmonic current
flow, 180Hz reading in a 60Hz system).
8. To freeze the digital display, press the HOLD
pushbutton.
9. To measure peak amperes, pre
s
s the 1mS PEAK
pushbutton (PEAK displayed).
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