Watlow PPC-2000 - Manual (Page 97)

PPC-2000 User’s Guide Chapter 2: Hardware Installation
Doc.# 30002-00 Rev 2.3 Watlow Anafaze 73
Using Snubbers for Relay Outputs
Relay contacts can arc and/or generate EMI. Over time, arcing
will shorten the life of relay contacts and EMI can disrupt
system functions. Use snubbers—a resistor and capacitor in
series— to protect against EMI and lengthen relay life.
The capacitor should be non-polarized and may be metallized
polyester film or metallized polypropylene and the voltage
rating must be 600Vdc/250Vac. The resistor may be carbon
composition or carbon film. It should be 0.5 or 1 watt with 5%
tolerance. Use 1 watt if the contacts are used in a rapid cycling
application.
The following values are acceptable for most applications using
the PPC-2061 and PPC-2062 relay output modules:
• Resistor: 120 Ω
• Capacitor: 0.47 µ F
Install the snubber across the contacts or the load. Generally,
it performs more reliably across the contacts.
Figure 2.61 Snubber Connections
H
120/240Vac C R
Preferred Method
Contacts
Load
Alternative Method
N