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CVHE-SVU01E-EN
64
When less than 2.5 seconds remain
before compressor start, a starter test
is conducted to verify contactor
states prior to starting the
compressor. The following test or
start sequence is conducted for
‘‘Wye-Delta’’ starters: Also refer to
Figure 24.
A. Test for transition complete
contact open (2A1-J12-2) –160 to 240
msec. An MMR diagnostic will be
generated if the contact is closed.
B. Delay time - 20 msec.
C. Close start contactor (2K1) and
check for no current - 500 msec. If
currents are detected, the MMR
diagnostic ‘‘Starter Fault Type I’’ is
generated.
D. Stop relay (2A1-J10-3 to 1) closes
for one second for test “C” above.
E. Delay time - 200 msec. (Opens
2K1).
F. Close shorting contactor, (2K3) and
check for no current - one second. If
currents are detected the MMR
diagnostic ‘‘Starter Fault Type II’’ is
generated. (Starter Integrity test)
G. If no diagnostics are generated in
the above tests, the Stop Relay (2A1-
J10) is closed for 2 seconds and the
Start Relay (2A1-J8) is closed to
energize the start contactor (2K1). The
shorting contactor (2K3) has already
been energized from (F) above. The
compressor motor (4M1) starts in the
‘‘Wye’’ configuration, an auxiliary
contact (2K1-AUX) locks in the start
contactor (2K1) coil.
H. After the compressor motor has
accelerated and the maximum phase
current has dropped below 85
percent of the chiller nameplate RLA
for 1.5 seconds, the starter transition
to the ‘‘Delta’’ configuration is
initiated.
J. The transition contactor (2K4) is
closed through relay 2A1-J2, placing
the transition resistors (2R1, 2R2, and
2R3) in parallel with the compressor
motor windings. The run relay (2A1-
J6-3 to 1) is closed.
K. The shorting contactor (2K3) is
opened through the opening of relay
2A1-J4 100 msec after the closure of
the transition relay 2A1-J2, and the
run relay 2A1-J6.
L. The run contactor (2K2) is closed
through auxillary contacts on the
shorting contactor (2K3), shorting out
the transition resistors. This places
the compressor motor in the ‘‘Delta’’
configuration and the starter module
waits to look for this transition for
about 2.3 seconds through the
closure of the transition complete
contacts 2K2-Aux at module 2A1-J12
input)
M. The starter module must now
confirm closure of the transition
complete contact (2K2-AUX) within
2.5 seconds after the shorting relay
(2A1-J4) is opened. Finally, the
transition relay (2A1-J2) is opened de-
energizing the transition contactor
(2K4) and the compressor motor
starting sequence is complete. An
MMR diagnostic will be generated if
the transition complete contacts (2K2-
AUX) do not close. A diagram of this
test or start sequence is shown in
Figure 24.
Control Sequence
of Operation