Master/Follower Operation Application - Danfoss VLT AQUA Drive Design Manual

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VLT AQUA Drive Design Guide
Min. Reference
Max. Reference
Initial Ramp Up Time
Final Ramp Down Time
Normal Ramp Up Time
Normal Ramp Down Time
Motor Min. Speed
Motor Max. Speed
Use the "Closed Loop" wizard under "Quick Menu_Funtion_Setup", to easily set up the feedback settings in the PID controller.
Pipe Fill Mode
Pipe Fill Enable
Pipe Fill Rate
Filled Set Point

6.1.15. Master/Follower Operation Application

Application Description
The system used as example contains 4 equal sized pumps in a water distribution system. They are each connected to a Danfoss VLT AQUA Drive. A
pressure transmitter with an analogue output format of 4-20mA is used as feedback and connected to the drive named the 'master drive'. The master
VLT Extended Cascade Controller Option MCB-101
drive also includes the Danfoss
system.
Arguments for using a 'master / follower' setup instead of the standard cascade control mode could be:
• In old and weak pipe system where huge pressure surges can lead to leakage, the high performance of the master / follower mode can be a
real benefit.
• In constant pressure water systems the pumps can be operated in the most energy efficient way by using Master / follower operation.
• In systems with large variances in flow, the fast reacting Master / Follower mode will safely and fast maintain a constant pressure.
• Very easy installation - no need for external equipment. The drives can be delivered in IP55 or even IP66, which means no need for panels,
except for fuses.
Issues to keep in mind
Compared to traditional cascade control the number of running pumps is controlled by speed instead of feedback. To obtain the highest energy saving
the stage on and off speed must be set correctly according to the system. To understand the principle better, please note figure 1.
Par. 3-01
Par. 3-02
Par. 3-84
Par. 3-88
Par. 3-41
Par. 3-42
Par. 4-11
Par. 4-13
Par. 29-00
Par. 29-04
Par. 29-05
. The purpose of the system is to maintain a constant pressure in the
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MG.20.N4.02 - VLT is a registered Danfoss trademark
6. Application Examples
(30 Hz)
(50/60 Hz)
(2 sec.)
(2 sec.)
(8 sec. depending on size)
(8 sec. depending on size)
(30 Hz)
(50/60 Hz)
(Feedback units/sec.)
(Feedback units)
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