Trane CVGF1000, Installation, Operation & Maintenance Manual

Page: 102 / 128

Machine Protection and Adaptive Control
Momentary Power Loss (MPL) Protection
Momentary power loss detects the existence of a power loss to the compressor motor
and responds by initiating the disconnection of the compressor motor from the power
source.
Power interruptions of less than 30 line-cycles are defined as momentary power loss-
es. Tests have shown that these short-term power interruptions can be damaging to
the motor and compressor if the chiller is reconnected to the line while the motor and
line phases do not match. The chiller will be shut down when a MPL is detected and
will display a non-latching diagnostic indicating the failure.
The oil pump will be run for the post-lube time period when power returns. The com-
pressor and compressor motor are protected from damage from large torques and in-
rush currents resulting from reconnecting the compressor motor to the power source
following a momentary loss of power.
MPLs greater than 2 or 3 cycles are detected resulting in unit shut down. Disconnec-
tion from the line is initiated within 6 line-cycles of the power loss. MPL protection is
active anytime the compressor is in the running mode. (The transition complete input
has been satisfied.)
Note: MPL is defaulted to enabled however can be disabled, if required using UT ™.
Machine Protection and Adaptive Control
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