General Description - Danfoss VLT AQUA Drive Design Manual

®
VLT AQUA Drive Design Guide 3. VLT AQUA Selection
3.6.10. Introduction to the Extended Cascade Controller
Cascade control is a common control system used to control parallel pumps or fans in an energy efficient way.
The Extended Cascade Controller option provides the capability to control multiple pumps configured in parallel in a way that makes them appear as a
single larger pump.
When using the Extended Cascade Controller, the individual pumps are automatically turned on (staged) and turned off (de-staged) as needed in order
3
to satisfy the required system output for flow or pressure. The speed of pumps connected to VLT AQUA Drives is also controlled to provide a continuous
range of system output.
The Extended Cascade Controller is an optional hardware and software component that can be added to the VLT AQUA Drive. It consists of an option
board containing 3 relays that is installed in the B option location on the Drive. Once the option is installed the parameters needed to support the Extended
Cascade Controller functions will be available through the control panel in the 27-** parameter group. The Extended Cascade Controller offers more
functionality than the Basic Cascade Controller. It can be used to extend the Basic Cascade with 3 relays.
While the Cascade controller is designed for pumping applications and this document describes the cascade controller for this application, it is also possible
to use the Extended Cascade Controller for any application requiring multiple motors configured in parallel.

3.6.11. General Description

The Extended Cascade Controller software runs from a single VLT AQUA Drive with the Extended Cascade Controller option card installed. This Drive is
referred to as the Master Drive. It controls a set of pumps each controlled by a Danfoss VLT Drive or connected directly to mains through a contactor or
through a soft starter.
Each additional VLT Drive in the system is referred to as a Follower Drive. These Drives do not need the Extended Cascade Controller option card installed.
They are operated in open loop mode and receive their speed reference from the Master Drive. The pumps connected to these Drives are referred to as
Variable Speed pumps.
Each additional pump connected to mains through a contactor or through a soft starter is referred to as a Fixed Speed pump.
Each pump, variable speed or fixed speed, is controlled by a relay in the Master Drive. The VLT AQUA Drive with the Extended Cascade Controller option
card installed has five relays available for controlling pumps. 2 relays standard in the drive and additional 3 relays on the option card MCO 101.
The Extended Cascade Controller is capable of controlling a mix of variable speed and fixed speed pumps. Possible configurations are described in more
detail in the next section. For simplicity of description within this manual, Pressure and Flow will be used to describe the variable output of the set of
pumps controlled by the cascade controller.
77
®
MG.20.N4.02 - VLT is a registered Danfoss trademark