Flow Compensation - Danfoss VLT FC 102 Programming Manual

Parameter Descriptions
22-77 Minimum Run Time
Range: Function:
NOTICE
0 s [ 0 - par.
*
22-76 s]
Does not work in cascade
mode.
Sets the minimum run time after a
normal start command (start/jog/
freeze). Any normal stop command
is disregarded until the set time has
expired. The timer starts counting
following a normal start command
(start/jog/freeze).
A coast (inverse) or an external
interlock command overrides the
timer.

3.20.7 22-8* Flow Compensation

Sometimes it is not possible for a pressure transducer to
be placed at a remote point in the system, and it can only
be placed close to the fan/pump outlet. Flow compen-
sation operates by adjusting the setpoint according to the
output frequency, which is almost proportional to flow,
thus compensating for higher losses at higher flow rates.
H (required pressure) is the setpoint for closed-loop
DESIGN
(PI) operation of the frequency converter and is set as for
closed-loop operation without flow compensation.
It is recommended to use slip compensation and RPM as
unit.
Illustration 3.61 Flow Compensation
M0010001
Programming Guide
NOTICE
When flow compensation is used with the cascade
controller (parameter group 25-** Cascade Pack
Controller), the actual setpoint does not depend on
speed (flow), but on the number of pumps cut in. See
Illustration 3.62:
H
Set Point
H
P22-87
Illustration 3.62 Number of Pumps
There are 2 methods which can be employed, depending
on whether or not the speed at system design working
point is known.
Danfoss A/S © 10/2019 All rights reserved.
H
(head)
DESIGN
MIN
1 2
3
3
Number of pumps
209
3