CB Watch 3 User Manual
v6.3 - May 2019
Page 63 of 100
Mean coil current
Using historical data, we can determine the minimum and maximum values of the mean
coil current recorded. We can use them, as shown in the table below, to calculate the
max threshold for both opening and closing operation:
Opening
Closing
Nominal DC Voltage
A
Coil resistance
C
D
Max mean coil current
(A/C)x((1+p)/100)
(A/D)x((1+p)/100)
Figure 99
–
Mean coil current max threshold calculation
Where
a percentage “p” margin
is added to avoid spurious alarms.
If this function is not being monitored and no sensor is present, then the values should be
set as such to avoid any erroneous alarm:
HMI: Settings / Analogue channels
Figure 100
–
Coil current and charge default settings
Coil charge
By looking at the historical data, we can determine the minimum and maximum values of
the coil currents recorded and the time the coil is energised (which should be roughly
equal to the reaction time measured). We can use them, as shown in the table below, to
calculate the min and max coil charge for both opening and closing operation:
Opening
Closing
Minimum
Maximum
Minimum
Maximum
Coil current
A
B
C
D
Time
E
F
G
H
Coil charge
(AxE)x((1-p)/100) (BxF)x((1+p)/100)
(CxG)x((1-p)/100)
(DxH)x((1+p)/100)
Figure 101
–
Coil charge alarm threshold calculation
Where
a percentage “p” margin
is subtracted from the lowest figure or added to the
highest figure observed to avoid spurious alarms.
