Application Engineering
B U L
L E
T I N
AE8-1386 R1
Digital Compressor Regulation
The pressure is adjusted by a PI regulation.
Pressure
SET + Pbd/2
SET + Pbd/2*(PMA/100)
SET
SET - Pbd/2*(PM/100)
SET - Pbd/2
Time
Triac 100
0
Sut
Time
tdS
Compressor
Status
DGS
C1
C2
ton
don
Time
toF
doF
Time
Figure 8 - Digital Compressor Regulation
Regulation Start: Increasing Capacity
a. The regulation starts when the suction
pressure (temperature) increases and reaches
the value SET-Pbd/2+(Pbd*10%)/100. At
first, if available, the digital compressor is
powered, and it is modulated in PWM mode.
NOTE: At start up the valve is energized for
two seconds.
b. Within the adjustment range (SET-Pbd/2 ÷
SET+Pbd/2) the digital scroll compressor is
activated in PWM mode in accordance with the
value of the control variable. (NOTE: When the
TRIAC is on, the compressor is unloaded; when
the TRIAC is off, the compressor is loaded).
c. When the pressure is greater than [SET +
Pbd/2] and the TRIAC output is already at
maximum, if applicable, the second compressor is
started after the “don” delay time.
© 2013 Emerson Climate Technologies, Inc.
Printed in the U.S.A.
NOTE: If the Digital compressor is not available due
to pre-set time delays or otherwise, and the pressure
exceeds the value SET +Pbd/2, the fixed compressor
(if available) would be started.
Decreasing Capacity and Regulation Stop
a. When the pressure is lower than [SET - Pbd/2],
the DIGITAL compressor is still modulated to
minimum capacity for 5 seconds.
b. At the end of the 5 seconds the load with more
working hours is shut down. If the load must stay
on because 10 seconds is not over yet, the next
load is considered, and so on until a load that
can be shut down is available.
c. This procedure continues with all active loads,
with the shutdowns spaced out by the doF time
setting.
d. When only the digital compressor remains on, at
the end of the doF time the digital compressor
is shut down too.
14
To Next Page
Loading...
