Rockwell Automation Publication 440R-UM013E-EN-P - March 2017 27
Power, Ground, and Wire Chapter 3
Surge Suppressors
Because of the potentially high current surges that occur when switching
inductive load devices, such as motor starters and solenoids, the use of surge
suppression to help protect and extend the operating life of the relays is
required. By adding a suppression device directly across the coil of an inductive
device, you prolong the life of the outputs. You also reduce the effects of
voltage transients and electrical noise from radiating into adjacent systems.
Figure 17
shows an output with a suppression device. We recommend that you
locate the suppression device as close as possible to the load device.
For outputs that use 24V DC, we recommend 1N4001 (50V reverse voltage)
to 1N4007(1000V reverse voltage) diodes for surge suppression for the OSSD
safety outputs (Figure 17
). The diode must be connected as close as possible to
the load coil.
For outputs that use 120V AC or 240V AC, we recommend metal oxide
varistors.
Figure 17 - Surge Suppressors
Example surge suppressors include the following catalog numbers:
• 100-FSD250 for Bulletin 100S contactors
• 1492-LD4DF terminal block with built-in 1N4007 diode
• 1492-JD3SS terminal block with built-in varistor
K2K1
for VAC supply
V common
Metal Oxide Varistors Diodes
K2K1
for VDC supply
V common
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