Cascade Controller Option
Description of choice:
Set the desired feedback minimum within the
programmed minimum and maximum in Quick Menu
items 14 and 15. The process unit is selected in
Quick menu item 13,
Process Units
.
NB!:
Factory setting is for a single 4 - 20 mA current
signal transmitter for process feedback. In
all other cases, see instructions in Chapter
10,
Feedback Transmitter Wiring
.
Quick Menu 029 Par. 419 Setpoint 2
(SETPOINT 2)
Value:
Feedback Min. to Feedback Max.
✭
0.000
Function:
The default feedback process is used when a pressure
feedback signal is measured at the outlet of the
pumps. The cascade controller uses the feedback to
estimate the setpoint required at various rates of flow.
Setpoint 2 is the maximum pressure required when
the system is running with all pumps at full capacity. A
theoretical value calculates pressure loss in the system
under maximum load. The controller adjusts the
loading based upon the number of pumps in operation.
The range is determined by Quick Menu item 14
(parameter 413,
Minimum Feedback
) and Quick Menu
item 15 (parameter 414,
Maximum Feedback
).
When the pressure feedback signal originates at
the far end of the system, the drive does not
need to compensate for system pressure changes
due to flow. For this system configuration, or
for two setpoint PID control, see
Alternative
Programming
at the end of this chapter.
Description of choice:
Set the desired feedback maximum within the
programmed minimum and maximum in Quick Menu
items 14 and 15. The process unit is selected in
Quick menu item 13,
Process Units
.
Quick Menu 031 Par. 722 Pump cycling
(PUMP CYCLING)
Value:
Enabled - Disabled
✭
Enabled
Function:
To achieve equal hours of operation, use of pumps
or fans can be cycled. Timers on the relay outputs
(relays 6, 7, 8, and 9) monitor the running hours of
each pump. In staging on, the relay with the least
hours is switched on. In destaging, the relay with the
most hours is switched off. Not operating a pump
over long time periods can create corrosion concerns.
If cycling is disabled, the controller follows the fixed
pattern of relay activation (6, 7, 8 and 9) regardless of
the running hours. Destaging is in the reverse order.
Description of choice:
Choose whether to enable or disable the function.
Quick Menu 032 Par. 319 Analog output,
terminal 42
(AO 42 FUNCTION)
Value:
Output, terminal 42
✭
Output current 4-20 mA
Function:
An analog/digital output is available through terminal
42 and can be programmed to show a status or an
analog value such as frequency. For the analog output,
there are three types of output signals: 0 to 20 mA, 4
to 20 mA, or 0 to 32000 pulses. The pulse rate is set
by parameter 320,
Terminal 42, Output, Pulse Scaling
.
Description of choice:
Set the output of terminal 42 to
Output Frequency
(pulse sequence)
, (OUT.FREQ.PULSE) for Master/Slave
operation as shown in the wiring diagram in Chapter
4. Using frequency pulse is a reliable way of providing
the same speed reference to all slave drives. Current
output is limited to two slave drives.
System pressure and flow requirements can often be
generated using parallel pumps at different efficiencies.
The cascade controller can automatically configure
the number of pumps in operation to achieve the
highest system efficiency. Running three pumps at full
MG.60.I3.02 - VLT is a registered Danfoss trademark
48