Range
Relay position Notes
the deadband value. The
[Regulator] increase*
and
[Regulator] decrease
* relays remain
deactivated continuously.
See point 6 on the figures below.
*Note: [Regulator] is either GOV, or AVR.
If the output is in either the constant or the variable range, the controller activates the configured relay (governor increase or
decrease, or AVR increase or decrease) for the required time. The figures below show how the time decreases from the value set for
Period time
to the value set for
Minimum ON time
as the measured value gets closer to the set point for high
Kp
values and low
Kp
values. The
Maximum ON time
parameter is set to 100 %.
Figure 6.2
Up and down relay on time for different deviations from the set point
Frequency [Hz]
Relay up
on time [%]
Relay down
on time [%]
100
50
100
50
75
25
25
75
High Kp
Low Kp
1
2
3
4
5
6
Figure 6.3
Relay action based on measurements at the end of the period time
mi
n
mi
n
mi
n
mi
n
Period [ms]
OFF
ON
mi
n
Relay
status
1
2
3
4
5
6
Period time
Pulse properties
A relay control pulse has three main properties:
•
Period time
•
Minimum ON time
•
Maximum ON time
The
Period time
is measured from the start time of one pulse to the start time of the next pulse.
DESIGNER'S HANDBOOK 4189340911K UK
Page 172 of 521
