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1.2.5.1
Sensorless Vector Flow Control
Sensorless Vector control mode does not use a feedback signal that monitors the flow rate of the process
fluid to the controller. Sensorless Vector control uses a flow rate versus speed algorithm. Flow rates
and speed are entered via a user assisted drawdown calibration procedure in order to derive flow
accuracy (See Section 8.1.1 Open Loop Pump Flow Calibration). The user provides 2 points of
calibration, one point at high speed/flow (maximum motor RPM recommended) and a second point
recommended at low motor speed /minimum flow. These 2 points, once characterized, provide a linear
flow relationship for the positive displacement pump application. The flow curve below shows a user's
two point calibration. Once flows are measured, a speed versus flow conversion is utilized to adjust all
new flow set points. Note: Stroke length must remain constant for sensorless vector control.
Changing stroke length requires recalibration.
1.2.5.2
Closed Loop Flow Control
Closed loop flow control utilizes an analog flow meter in conjunction with an internal PID control
algorithm, providing excellent flow control by maintaining process flow set point. Flow meter
feedback must be in the form of a 4-20 mA signal representing process flow rates. The flow meter
should be located as close as possible to the pump in order to provide a measurement of the current
process flow rate without flow rate time lag introduced into the feedback loop (delayed flow readings
will cause flow stability issues). The analog flow signal (see flow meter setup Section 7.1.2 Analog
Input 2 – Flow meter Feedback for details) is fed into MPC Vector Analog Input 2, and is activated in
the System Setup menu under the sub-category of Flow Meter.
SPEED SETPOINT (OPEN LOOP
FLOW CONTROL – NO
FLOWMETER)
25
Turndown
Limit
Reached
Point 2
2.4
(Speed2, Flow2)
175
Speed Setpoint
(Handheld Remote)
Figure 1-2 Open Loop Flow Calibration Curve
7
Point 1
(Speed1, Flow1)
1750
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