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Triangle / star / off 234, D / y / off – West Control Solutions KS98-1 User Manual

Page 234

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D / Y / off

The principle is identical to the control behaviour of a 2-point controller with additional contact.

Output Y2 is used for switchover of the connected circuit between “

D” and “Y”. Output Y1 switches the heating ener-

gy on and off.

E.g. for temperature control with electrical heating (inverse operation) or cooling (direct operation).

Cycle time Tp1 must be adjusted as follows: Tp

Tu

1

0 25

<=

·

,

With higher Tp1, oscillations must be expected. Tp1 cor-

responds to the minimum cycle time (time in seconds) at 50 % duty cycle.

PD action

(

Tn = 0 = switched off Tn = Î)

The working point is in the middle of the proportional band X

p1

at 50 % duty cycle.

For keeping the control variable constant, a defined amount of energy dependent of is required. This causes a perma -
nent control deviation, which increases with higher X

p1.

DPID action
By means of the I action, line-out without permanent control deviation is possible.

The static characteristic of a two-point controller is identical to the one of a continuous controller. The difference is
that a duty cycle instead of a linearly variable current signal is output (relay contact, logic signal 0/20mA or control
output 0/24V).

Working point Y

0

and cycle time Tp1 of the cycle at 50% are adjustable.

The shortest switch-on or off time is 100ms.

Controller

9499-040-82711

III-234

Control behaviour

Output Y1 (heating)
Output Y2 (add. contact)

Process value

Setpoint

Xn100

Xn0

W0

Weff

W100

100%

0%

Y1Â

Y2Â

Xeff

Xp1

LW

Xsd2

actual

working point

Fig.: 57

Fig. Static operating principle
of the

D / Y / off function