Master-Follower Configuration - Danfoss VLT AQUA Operating Instructions Manual

Application Types
NOTICE
If the pumps are not equal in size or if 2 relays per
pump are used, a Mixed Pump Configuration has to be
chosen.
For the configuration shown in Illustration 2.3, relay
selections in parameter group 27-7* Connections are as
follows
27-70.0 RELAY 1→ [73] Pump 2 to Mains
27-70.1 RELAY 2 → [74] Pump 3 to Mains
27-70.9 RELAY 10 → [75] Pump 4 to Mains
27-70.10 RELAY 11→ [0] Standard Relay
27-70.11 RELAY 12→ [0] Standard Relay
NOTICE
Pressure fluctuations during staging/de-staging
transitions may occur and it may be less energy efficient
than the master-follower configurations.
2
T 12
DI18
Start
U / I
P
Pressure
Transmitter
0 - 10 V
0 - 20 mA or
4 - 20 mA
Illustration 2.4 Basic Wiring Principle (Example)
®
VLT AQUA Drive MCO 101/MCO 102
Master
with
MCO 101/ 102
DO 27
R 1
2
R 2
T 54
T 20
T 55
Motor / Pump 1
100%
®
MI38C402 - VLT is a registered Danfoss trademark

2.2.2 Master-Follower Configuration

The master-follower cascade control mode offers the best
performance, the most precise control and maximum
energy savings. It controls multiple equal sized pumps in
parallel, running all pumps at the same speed and stages
the pumps on and off according to system requirements.
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. In
this example terminal 27 of the master drive is used as
pulse output for the reference and the terminals 29 of the
follower drives are used as pulse input for this reference.
While the master drive is running in closed loop, the
followers are running in open loop. All follower drives are
connected to mains and motor in the same way as the
master drive.
Follower 1 Follower 2
DI 18
DI 18 DI 29
Motor / Pump 3
Motor / Pump 2
100%
DI 29
100%
7
2 2