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AYK550-UH User’s Manual
Start-Up
Group 81: PFA
This group defines a Pump and Fan Alternation (PFA) mode of operation. The major
features of PFA are:
• The AYK550 controls the motor of pump no. 1, varying the motor speed to control
the pump capacity. This motor is the speed regulated motor.
• Direct line connections power the motor of pump no. 2 and pump no.3, etc. The
AYK550 switches pump no. 2 (and then pump no. 3, etc.) on and off as needed.
These motors are auxiliary motors.
• The AYK550 PID control uses two signals: a process reference and an actual
value feedback. The PID controller adjusts the speed (frequency) of the first
pump such that the actual value follows the process reference.
• When demand (defined by the process reference) exceeds the first motor’s
capacity (user defined as a frequency limit), the PFA automatically starts an
auxiliary pump. The PFA also reduces the speed of the first pump to account for
the auxiliary pump’s addition to total output. Then, as before, the PID controller
adjusts the speed (frequency) of the first pump such that the actual value follows
the process reference. If demand continues to increase, PFA adds additional
auxiliary pumps, using the same process.
• When demand drops, such that the first pump speed falls below a minimum limit
(user defined by a frequency limit), the PFA automatically stops an auxiliary
pump. The PFA also increases the speed of the first pump to account for the
auxiliary pump’s missing output.
• An Interlock function (when enabled) identifies off-line (out of service) motors, and
the PFA skips to the next available motor in the sequence.
An Autochange function (when enabled and with the appropriate switchgear)
equalizes duty time between the pump motors. Autochange periodically increments
the position of eAYK motor in the rotation – the speed regulated motor becomes the
last auxiliary motor, the first auxiliary motor becomes the speed regulated motor, etc.
Group 81: PFA
Code Description Range
Resolution
Default
S
8103
REFERENCE STEP 1
0.0…100.0%
0.1%
0.0%
Sets a percentage value that is added to the process reference.
• Applies only when at least one auxiliary (constant speed) motor is running.
• Default value is 0%.
Example:
An AYK550 operates three parallel pumps that maintain water pressure in a pipe.
• 4011
INTERNAL
SETPNT
sets a constant pressure reference that controls the pressure in the pipe.
• The speed regulated pump operates alone at low water consumption levels.
• As water consumption increases, first one constant speed pump operates, then, the second.
• As flow increases, the pressure at the output end of the pipe drops relative to the pressure measured at the input
end. As auxiliary motors step in to increase the flow, the adjustments below correct the reference to more closely
match the output pressure.
• When the first auxiliary pump operates, increase the reference with parameter 8103
REFERENCE
STEP
1.
• When both auxiliary pumps operate, increase the reference with parameter 8103 reference step 1 + parameter
8104 reference step 2.
• When three auxiliary pumps operate, increase the reference with parameter 8103
REFERENCE
STEP
1 + parameter
8104
REFERENCE
STEP
2 + parameter 8105
REFERENCE
STEP
3.
Summary of Contents for AYK 550
Page 256: ...D1 AYK550 UH User s Manual Appendix D Appendix D Base Drive Drawing 205662 Drawings Fig 1...
Page 257: ...AYK550 UH User s Manual D2 Appendix D Base Drive w Fused Disconnect Drawing 205648 Fig 2...
Page 258: ...D3 AYK550 UH User s Manual Appendix D Base Drive w Non Fused Disconnect Drawing 205647 Fig 3...
