Rockwell Automation System Design for the Control of Electrical Noise - Manual (Page 54)

Publication GMC-RM001A-EN-P — July 2001
6-2 Contact Suppression
Note: Sometimes the supply to a group of zero-crossing Triac outputs
is switched by a mechanical contact for safety purposes.
Suppress at the contact in this case.
Methods of AC Contact Suppression
The typical RC suppressor circuit (shown below) consists of a 0.1
µ
F
capacitor in series with a 100 ohm resistor. These components are
readily available from many suppliers.
Figure 6.1
RC suppressor circuit
The typical RC plus transient absorber circuit (shown below) consists
of the RC network shown in Figure 6.1 in parallel with a transient
absorber. These are used in high current, high energy applications
such as motor starters. A three-phase contactor requires three
suppressors.
Figure 6.2
RC plus transient absorber circuit
0.1 µ F 100 ohms
0.1 µ F 100 ohms
Transient absorber