Brochure

ESG
8.568.56
8.568.56
8.56
28 VDC
1N4005
1N4753DC relay
+
–
A 28 VDC
1N4005
1N4753
+
–
1N4753
B
DC relay
115 VAC
V 130
LA 10 A
+
–
V 130
LA 10 A
C
AC relay
Fig. 11: Transient suppression techniques
Fig. 12: Comparison of zener diode and MOV characteristics
+
–
Peak pulse
current
Reverse
current
Knee
Leakage current
V
Z
V
I
+
–
Clamping voltage
Forward current
Zener diode, V-I characteristic
MOV V-I characteristic
Leakage current
V
I
+
–
Clamping voltage
Clamping voltage
Suppressors
When overvoltage transients occur, another form of
suppression may be required beyond the capabilities of
the snubber. One popular technique is to add a clamping
device across the SSR terminals that will absorb the
transient energy above a predetermined level.
Devices, such as zeners and MOVs, will conduct only at
the predetermined level and above, thereby sharing the
transient with the load. If it is unacceptable for the load
to receive any transient energy, the only solutions may
be suppression of the transient source, or an SSR with a
blocking capability higher than the transient.
Fig. 11 illustrates typical methods of suppressing tran-
sients across the SSR output "contacts" as well as
suppression of transients at the source which can be the
load itself for dc inductive type loads.