Rockwell Automation TDI16EIA 16-Channel Digital Input Termination Card - Manual (Page 8)

8 TDI16EIA October 2005 – Issue 3
Triguard SC300E
TRANSIENT SUPPRESSION
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, therefore, 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 Condinuous *Maximum current for continuous
overload
+70V **69Amps
8 to 20
µ
s
**Maximum peak pulse current
SUPPLEMENTARY INFORMATION
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.
Pins J1-1c and J2-SS are interconnected.
J1/J2 pins other than J1-1a, J1-1c, J2-1c and those listed in Table 2-2 are not connected.