( ^Eranrralsy Measurement and Phase Sequence Judgement
Al\ wamings
1. If the amplitude voltage of a frequency to be measured is lower than 25Y the
measurement might be inaccurate and the result is only for reference. The voltage limit
for a frequency measurement is 250V (mean effective value), measurement of a
voltage higher than the limit value is not allowed in case of eleckic shock or
instrument damage.
2. tn phase sequence judgement, to guarantee accurate judgement, before testing, please
make clear whether there is phase loss in the system that should have three phases by
making use of the live wires and make sure there is no phase loss.
5-1. Turn the switch to choose a frequency measuring range profile, then "kHz" should be
displayed.
5-2. Insert the insertion ends of the red probe and black probe into the VHZCXO'C
terminal and the COM terminal respctively.
5-3. Connect the pins of the probes to the two ends of the circuit to be measured, make
sure the contacts are reliable.
5-4. After the stabilization of reading, read the measured frequency value displayed on the
viewing screen. If the reading is"0l", it indicates the frequency measured exceeds the
measuring range.
5-5. To make a phase sequence jud8emenffiase press key t( ) to enter into the mode
of phase sequence judgement, then UUU will be displayed on the display screen,
insert the insertion ends of the phase sequence accessories into the COM and
VHZCXQ"C terminals of the instrument respectively.
5-6. Connect the yellodblack/red line clamp to the three testing endpoints, i.e., phase a,
nhacc ! and phase c, of the three-phase power source respectivejly. the display of
nrr - --- nn
nEL indicates positive phase sequence. The display of liU indicates the
existence of anti-phase or phase loss, in this case, please make the red lir^*;{rmn and
black line clamp replace each other and phase loss is indicat.6 6 *lU is still
displaced.
11
Graphic Representation Involving Connection Graph Involving Phase
Frequency Measurement Sequence Judgement
Typical Application in Phase Sequence Judgement?
The phase sequence refers to the three-phase sequence ananged in accordance with phase
angle sequence, positive phase sequence refers to the three-phase sequence l6anged in
cloclavise direction as shown in the picture below, reverse phase sequence refers to the
sequence arranged in the anticlockwise direction. Before the availability of a
phase-sequence meter, the electrician usually undertakes wire connection for a
tlree-phase motor andjudges the phase sequence via the rotation direction ofthe motor,
the motor rotation in positive direction indicates positive phase sequence, and the reversed
rotation ofmotor indicates reverse phase sequence. However, the absolute phase sequence
wiring of a three-phase power supply from power plant can not be distinguished through a
common phase-sequence judgement by a phase-sequence meter.
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Positive Phase Sequence I Positive phase sequence 2 Positive Phase Sequence 3
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