-46-
21.1 (continued)
The governor input (4-20 ma from the DE-2500 ) will be automatically adjusted within the user
programmed MINIMUM RPM to MAXIMUM RPM range to satisfy the PRIMARY CONTROL
setpoint.
Restating the section above, once the CAPACITY CONTROL OUTPUT reaches 100% the DE-
2500 system will attempt to satisfy the PRIMARY CONTROL setpoint with the CAPACITY
OUTPUT held at its maximum value (100%) by adjusting the RPM. When controlling the
speed, the DE-2500 will automatically adjust the engine speed by means of the governor
setpoint to any value between the MINIMUM RPM and the MAXIMUM RPM set by the user
when programming the unit. When conditions change in a manner which requires a reduction
in compressor throughput, the DE-2500 will first reduce the speed. The speed will be reduced
to the MINIMUM RPM value before the CAPACITY CONTROL OUTPUT will be changed. That
is, if the PRIMARY CONTROL setpoint cannot be satisfied by running at the MINIMUM RPM
and 100 % CAPACITY ( compressor throughput still too high), then the DE-2500 will begin
reducing the CAPACITY OUTPUT to reach the setpoint. The basic control is made to function
in this manner since RPM CONTROL of compressor throughput is the most efficient for both
screw and reciprocating type machines, but both RPM and CAPACITY CONTROL are often
needed to cover a wider range of compressor throughput requirements.
COMPRESSOR LOAD CONTROL SEQUENCE:
MAXIMUM [----]
[---] [--]
ENGINE
RPM [-------] [--]
[---] [--]
MINIMUM [------------------] [------]
MAXIMUM [------------------------------------]
[-] [--]
CAPACITY [-] [--]
CONTROL
[--]
[--]
MINIMUM [--]
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