Type 2865

9 | 13

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6.2. Exemplary characteristic curve of a proportional valve

Note:

In continuous flow applications, the choice of an appropriate valve size is much more important than with on/off valves. The optimum

size should be selected such that the resulting flow in the system is not unnecessarily reduced by the valve. However, a sufficient

part of the pressure drop should be taken across the valve even when it is fully opened.

Recommended value: Δp

valve > 25 % of total pressure drop within the system

Otherwise, the ideal, linear valve curve characteristic is changed.

If the differential pressure (difference between inlet and outlet pressure) exceeds half the value of the nominal pressure discontinuities

may occur.

For that reason take advantage of Bürkert competent engineering services during the planning phase!

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

K

V

K

VS

0

5

10 [V]

4

12

20 [mA]

0

10

20 [mA]

7.

Product operation

7.1. Control unit

Valve control takes place through a PWM signal (pulse-width modulation). The duty cycle of the PWM signal determines the coil

current and hence the position of the plunger.

The Bürkert control electronics Type 8605 (see relevant data sheet Type 8605 ) converts an analogue signal to a reference value cor­

responding to the valve type PWM signal and provides additional functions such as temperature compensation (coil heating), ramp

function and the adjustment of min. and max. duty cycle/coil current for the control range.

Please note the sizing comments for such a control valve in chapter “6.2. Exemplary characteristic curve of a proportional valve”

on page 9.