
3.1.6 Unequal Size Pump Configuration
The Unequal Size Pump configuration supports a limited mix of fixed-speed pumps in different sizes. It provides for the largest range of system output
with the smallest number of pumps.
Figure 3.6: Example
For this configuration, relay selections in Group 27-7* “Connections” are as follows:
27-70 RELAY 1
→
[73] Pump 2 to Line Voltage
27-71 RELAY 2
→
[74] Pump 3 to Line Voltage
27-72 RELAY 10
→
[75] Pump 4 to Line Voltage
27-73 RELAY 11
→
[0] Standard Relay
27-74 RELAY 12
→
[0] Standard Relay
Not all configurations of unequal size pumps are valid. For a configuration to be valid, it must be possible to stage pumps in increments of 100% of the
size of the master drive’s variable speed pump. This is necessary since the variable speed pump must be able to control the output between the fixed-
speed stages.
Valid Configurations
100% is defined as the maximum flow produced by the pump connected to the master drive. The fixed-speed pumps must be multiples of this size.
Variable Speed
Fixed Speed
100%
100% + 200%
100%
100% + 200% + 200%
100%
100% + 100% + 300%
100%
100% + 100% + 300% + 300%
100%
100% + 200% + 400%
100% + 100%
200%
100% + 100%
200% + 200%
(Other valid configurations are possible)
Invalid Configurations
Invalid configurations will still run but will not stage on all of the pumps. This is done to allow for limited operation if a pump fails or is interlocked in this
configuration.
3 Supported Configuration
Extended and Advanced Cascade Controller
Option
3-6
MI.38.C2.22 - VLT
®
is a registered Danfoss trademark
3