PMA Digital 280-1, Operating Manual

Page: 21 / 52

The control parameters can be determined from the values calculated for delay
time T
u
, maximum rate of increase v
max
, control range X
h
and characteristic K
according to the formulas given below. Increase Xp, if line-out to the set-point
oscillates.
Controller
Digital 280-1 Manual tuning 21
y = correcting variable
Y
h
= control range
Tu = delay time (s)
Tg = recovery time (s)
X
max
= maximum process value
V
max
=
Xmax
Tg
=
{
{
x
t
= max. rate of
increase of process value
Parameter adjustment effects
Parameter Control Line-out of disturbances Start-up behaviour
Pb1 higher increased damping slower line-out slower reduction of duty cycle
lower reduced damping faster line-out faster reduction of duty cycle
td1 higher reduced damping faster response to disturbances faster reduction of duty cycle
lower increased damping slower response to disturbances slower reduction of duty cycle
ti1 higher increased damping slower line-out slower reduction of duty cycle
lower reduced damping faster line-out faster reduction of duty cycle
Formulas
K = Vmax * Tu controller behavior Pb1 [phy. units] td1 [s] ti1 [s]
With 2-point and
3-point controllers,
the cycle time must
be adjusted to
t1 / t2 £ 0,25 * Tu
PID 1,7 * K 2 * Tu 2 * Tu
PD 0,5 * K Tu OFF
PI 2,6 * K OFF 6 * Tu
P K OFF OFF
3-point-stepping 1,7 * K Tu 2 * Tu
Tu
Tg
t
x
y
100%
0%
t
Yh
Xmax
{ X
{ t