Sensorless Operation - Armstrong 4302 IVS Series Installation And Operating Instructions Manual

6.0

SENSORLESS OPERATION

Sensorless control is an innovative concept in glanded
circulating pumps. Pump performance and characteristic
curves for ten different speeds are embedded in the
memory of the speed controller during manufacture. This
data includes power, pressure and flow across the flow
range of the pump. During operation, the power and
speed of the pump are monitored, enabling the controller
to establish the hydraulic performance and position in the
pumps head-flow characteristic.
These measurements enable the pump to continuously
identify the head and flow at any point in time, giving ac-
curate pressure control without the need for external feed-
back signals. Patented software technology within the
controller ensures trouble-free operation in all conditions.
Incorporating the pumps hydraulic data into the controller
and removing sensors results in true integration of all
components and removes the risk of sensor failure.
6.1 DEFAULT OPERATING MODE - QUADRATIC
PRESSURE CONTROL
The default control mode for IVS Sensorless pumps
'Quadratic Pressure Control' where the controller is set to
control the speed according to a 'control curve' between
max and min flow (see above diagram). It is widely recog-
nised that fitting a differential pressure sensor at the most
remote load, across the supply piping and return piping
encompassing the valve & coil set, is the best installation
scheme for energy efficiency.
IVS Sensorless pumps can replicate this control without
the need for the remote sensor. As the flow required by
the system is reduced, the pump automatically reduces
the head developed according to the pre-set control curve.
It is often found that using a remote differential pressure
sensor to sense the pressure across a remote load could
theoretically result in loads close to the pump being un-
der-pumped. The situation would be where the load at a
loop extremity is satisfied and the control valve closes
while a load close to the pump needs full flow. The prob-
ability of this occurring is remote but it is possible. One
answer to this is to move the sensor closer to the pump
(two-thirds out in the system is a popular recommenda-
tion) although physically re-positioning the sensor at com-
missioning stage can be a costly exercise. With Sensor-
less pump control it is possible to replicate the moving of
a sensor by adjusting the head setting 'Head Qmin'.
6.1.1 DESCRIPTION OF SETTINGS
The design duty head and flow of the pump (provided at
time of order) is defined by the controller as 'head working
point' and 'flow working point'. The minimum head (Head
Qmin) is defined as a percentage of the head working
point. The maximum controllable head (Head Qmax) is
the head developed when the pump reaches full speed
and is calculated by the other two head settings.
6.1.2 SETTING PARAMETERS FOR QUADRATIC
PRESSURE CONTROL

Parameter 716 - Enter the head (kPa) at design flow.

Parameter 717 - Enter the design flow (l/s).

Parameter 707 - Enter the minimum head requirement
(as a percentage of P716).

Parameter 705 - Quadratic Head should be set to 'ON'.

Parameter 798 - This is a calculated value from the
settings above and should not be changed.
6.2 CONSTANT PRESSURE CONTROL
IVS Sensorless pumps can be configured to maintain a
constant pressure in a system as the demand varies. This
effectively simulates the mounting of a differential pres-
sure sensor at, or near, the pump.
6.2.1 SETTING PARAMETERS FOR CONSTANT PRES-
SURE CONTROL

Parameter 716 - Enter the head (kPa) at design flow.

Parameter 717 - Enter the design flow (l/s).

Parameter 707 - Enter the minimum head requirement
(as a percentage of P716) which will be 100% for con-
stant pressure.

Parameter 705 - Quadratic Head should be set to 'OFF'.

Parameter 798 - This is a calculated value from the
settings above and should not be changed.
6.3 PROPORTIONAL PRESSURE CONTROL
Where a linear reduction in head is required with reducing
flow then the quadratic curve should be turned off.
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