10-10-2012, 04:28 PM
Phase Sequence Detector
[attachment=35964]
DESCRIPTION
The Models 108B (50/60 Hz) and Model 125C (400
Hz) Phase Sequence Detectors permit the operator to
quickly and easily determine proper phase sequence
(either ABC or CBA). This can be vitally important
information when installing, or making wiring changes to
motors, wattmeters, transformers, electrical
installations, power factor meters or generators.
To use, connect the Detector to any 3-phase circuit from
208 to 480 volts, Wye or Delta. Proper phase
sequence, and all phases present will illuminate the
ABC lamp. An open phase condition will illuminate both
lamps. If two or more phases are open, neither lamp will
illuminate. See the Condition Chart.
CONNECTION
Connect the three clip leads to the 3-phase power source.
Apply AC power. One of the detector lamps should
illuminate, indicating the phase sequence as connected. If
the desired phase sequence is not lit, change any two of
the three leads.
Read the 3-phase designation on the front panel; connect
the corresponding leads to your equipment.
If both lamps illuminate, check for a loss of voltage on one
of the three phases. If neither lamp illuminates, check for a
loss of voltage.
3-PHASE POWER BASICS
In 3-phase power there are three lines which carry the
voltage, normally designated as A-B-C. In some
installations however, they may be designated L1-L2-L3 or
T1-T2-T3. The phase sequence as generated is A-B-C.
As the voltage on these lines rotates through 360 degrees,
phase B lags phase A by 120 degrees; while phase C lags
phase A by 240 degrees. The voltage on each of these
lines vary as shown in figure 1, a graph of voltage versus
degrees of rotation.
If all phases are shown on the same graph, they would
appear as shown in figure 2.
Pictured on a rotating phasor diagram, the angle
between each phase is fixed at 120 degrees as they
rotate in unison at the line frequency (see figure 3).
In figure 4 you can see that if any two phases are
reversed, the direction of rotation will be in the opposite
direction. This reversal of the rotating sequence will
cause motors to run in the opposite direction. Many
other types of equipment are phase sensitive and will
not perform as intended if the phase sequence is
incorrect.
[attachment=35964]
DESCRIPTION
The Models 108B (50/60 Hz) and Model 125C (400
Hz) Phase Sequence Detectors permit the operator to
quickly and easily determine proper phase sequence
(either ABC or CBA). This can be vitally important
information when installing, or making wiring changes to
motors, wattmeters, transformers, electrical
installations, power factor meters or generators.
To use, connect the Detector to any 3-phase circuit from
208 to 480 volts, Wye or Delta. Proper phase
sequence, and all phases present will illuminate the
ABC lamp. An open phase condition will illuminate both
lamps. If two or more phases are open, neither lamp will
illuminate. See the Condition Chart.
CONNECTION
Connect the three clip leads to the 3-phase power source.
Apply AC power. One of the detector lamps should
illuminate, indicating the phase sequence as connected. If
the desired phase sequence is not lit, change any two of
the three leads.
Read the 3-phase designation on the front panel; connect
the corresponding leads to your equipment.
If both lamps illuminate, check for a loss of voltage on one
of the three phases. If neither lamp illuminates, check for a
loss of voltage.
3-PHASE POWER BASICS
In 3-phase power there are three lines which carry the
voltage, normally designated as A-B-C. In some
installations however, they may be designated L1-L2-L3 or
T1-T2-T3. The phase sequence as generated is A-B-C.
As the voltage on these lines rotates through 360 degrees,
phase B lags phase A by 120 degrees; while phase C lags
phase A by 240 degrees. The voltage on each of these
lines vary as shown in figure 1, a graph of voltage versus
degrees of rotation.
If all phases are shown on the same graph, they would
appear as shown in figure 2.
Pictured on a rotating phasor diagram, the angle
between each phase is fixed at 120 degrees as they
rotate in unison at the line frequency (see figure 3).
In figure 4 you can see that if any two phases are
reversed, the direction of rotation will be in the opposite
direction. This reversal of the rotating sequence will
cause motors to run in the opposite direction. Many
other types of equipment are phase sensitive and will
not perform as intended if the phase sequence is
incorrect.