Arbiter Systems 931A, Руководство по эксплуатации

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With Channel 1 set to “Van” and Channel 2 set to “Vbn”, the waveform
display will show the peak of “Vbn” 120 degrees after the peak of “Van”
for an “ABC” Phase Sequence. The waveform display always begins at
the zero crossing of the Channel 1 signal. Dashes displayed for the phase
sequence indicate that the Model 931A could not measure a valid “Vab to
Vac” phase. Phase rotation is determined by measuring “VcnVan”.
The second tabular display (Watt/VAR/VA Hour) replaces the total
power quantities with accumulated energy readings. The energy readings
are set to zero by pressing the RESTART key.
3.3.2.7 Vector Diagram
The Vector Diagram consists of a table of the measured voltages, currents
and phase angles along with their vector representation. The “A” phase
voltage vector is fixed in the horizontal direction. Positions of all other
vectors rotate according to their phase angle with respect to the “A” phase
voltage. Positive phase angle is denoted by counter-clockwise rotation.
The length of the vectors shows the relative amplitude of each phase. The
largest voltage and the largest current each have the longest vectors. A
vector with a length of less than one pixel is not displayed. All voltage
and current phases are made with respect to the “A” phase voltage. The
“A” phase voltage must be present for a proper Vector Diagram display.
3.3.2.8 Voltage and Current Sequence
The Voltage and Current Sequence display shows the measured voltages,
currents and phase angles in the top portion of the display. The bottom
half of the display shows the positive (V1, I1), negative (V2, I2) and zero
(V0,I0) sequence values. The Model 931A defines the positive sequence
as the values in the “ABC” direction and negative sequence as values in
the “CBA” direction. Also included is a computed value for the neutral
current amplitude and phase angle. All voltage and current phases are
made with respect to the “A” phase. The “A” phase must be present for
a proper Voltage and Current Sequence display.
Positive-Sequence Current (I1) and Voltage (V1) are the normal com-
ponents represented in balanced three-phase (3-wire and 4-wire) systems.
They are present in operating motor and generator windings.
Negative-Sequence Currents (I2) and Voltages (V2) are the components
in 3-phase systems that result from unbalanced phase-to-phase current and
voltage. They cause undesired heating in motor and generator windings.
Reversed phase sequence – ACB vs ABC – can be viewed as an extreme
negative sequence case.
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