Basler DECS-250, Instruction Manual

Page: 76 / 352

60 9440300990 Rev J
Limiters DECS-250
Figure 46. Inverse Time Characteristic for Takeover OEL
Primary and secondary setting groups provide additional control for two distinct machine operating
conditions. Each mode of takeover OEL operation (offline and online) has a low-level
A
, high-level
B
, and
time dial
C
setting.
Once the field current decreases below the dropout level (95% of pickup), the function is reset based on
the selected reset method
D
. The available reset methods are inverse, integrating, and instantaneous.
Using the inverse method, the OEL is reset based on time versus multiple of pickup (MOP). The lower the
field current level, the less time is required for reset. Inverse reset uses the following curve (Equation 12)
to calculate maximum reset time.
𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇
𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟
=
𝑅𝑅𝐶𝐶 × 𝑇𝑇𝑇𝑇
(
𝑀𝑀𝑀𝑀𝑀𝑀
𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟
) 2
− 1
Equation 12. Inverse Reset Time Characteristic
Where:
Time
reset
= maximum time to reset in seconds
RC = reset coefficient setting
E
<0.01, 100>
TD = time dial setting <0.1, 20>
MOP
reset
= multiple of pickup <1.03, 205>
For the integrating reset method, the reset time is equal to the pickup time. In other words, the amount of
time spent above the low level threshold is the amount of time required to reset.
Instantaneous reset has no intentional time delay.
In BESTCOMS Plus
®
, a plot of the takeover OEL setting curves is displayed. Settings enable selection of
the displayed curves. The plot can display the primary or secondary setting curves, the offline or online
settings curves, and the pick up or reset settings curves.