
CG Drives & Automation 01-7491-01r0
Functional description
145
The transition speed start is used to minimize a flow/
pressure overshoot when adding another pump. When an
additional pump needs to be switched on, the master pump
will slow down to the set transition speed start value, before
the additional pump is started. The setting depends on the
dynamics of both the master drive and the additional drives.
The transition speed is best set by trial and error.
In general:
•
If the additional pump has 'slow' start/stop dynamics,
then a higher transition speed should be used.
•
If the additional pump has 'fast' start/stop dynamics,
then a lower transition speed should be used.
Example
Max Speed = 1500 rpm
Min Speed = 200 rpm
TransS Start = 60%
When an additional pump is needed, the speed will be
controlled down to min speed + (60% x (1500 rpm - 200
rpm)) = 200 rpm + 780 rpm = 980 rpm. When this speed is
reached, the additional pump with the lowest run time
hours will be switched on.
Fig. 123 Transition speed start
Fig. 124 Effect of transition speed
The settle stop allows the process to settle after a pump is
switched off before the pump control continues. If an
additional pump is stopped D.O.L. (Direct On Line) or Y/
,
the flow or pressure can still fluctuate due to the 'rough'
start/stop method. This could cause unnecessary starting
and stopping of additional pumps.
During the Settle stop:
•
PID controller is off.
•
the speed is kept at a fixed level after stopping a pump
39E
TransS Start
Default:
60%
Range:
0-100% of total min speed to max speed
NOTE: If set to 100 %, the transition speed, when
starting pumps, is ignored and no speed adaption is
made.
I.e. the slave pump is started directly and speed of
the master pump is maintained.
(NG_50-PC-16_1)
Speed
Actual
Trans
Min
Switch on
procedure starts
Additional pump
Master pump
Flow/Pressure
Actual start
command of next
pump (RELAY)
39F
Settle Stop
Default:
0 s
Range:
0–999 s
Flow/Pressure
Transition speed
decreases overshoot
Time
Δ
Содержание FDU Series
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