Manual

8
TAI16AI
A
October
200
5
–
Issue 3
Triguard SC300E
TRANSIENT SUPPRESSIO N
A transient suppressor is fitted across each digital input channel input to the SC300E chassis.
It provides a discharge path for transient energy pulses that may appear on the digital input line
following
lightning strikes etc.
The suppressor is effectively a zener diode with a breakdown voltage just above that of the
normal supply voltage. In normal operation, therefor e, the suppressor does not conduct (apart
from leakage current). In the presence of a transient pulse, zener breakdown occurs. The
voltage developed across the suppressor varies to some extent with the pulse current and is
known
as the ‘clamping’ voltage.
The following characteristics are typical:
Table 2 - 1. Transient suppressor characteristics
Clamping
Voltage
Pulse
currents
Pulse
duration
Comments
+37V to +43V *1mA Continuous *Maximum current continuous overload
+70V **6gAmps
8 to 20  s
**Maximum
peak pulse current
SUPPLEMENTARY INFORM ATION
Table 2 - 2 lists the digital input channel wiring connections and associated fuses for connectors
J1 and J2.
Pin J1 - 1a is connected to the +ve bus (Figure 2 - 3 ). Pins J1 - 1c and J2 - 1c are interconnected.
J1/J2
pins other than J1 - 1a, J1 - 1c, J2 - 1c and those listed in Table 2 - 2 are not connected.