Rockwell Automation 1336T Wiring and Grounding Guide, (PWM) AC Drives - Manual (Page 79)

Rockwell Automation Publication DRIVES-IN001M-EN-P - March 2014 79
Electromagnetic Interference Chapter 6
This table contains examples that illustrate methods for mitigating transient
interference.
Examples of Transient Interference Mitigation
Example 1
A contact output controls a DC control
relay.
The relay coil requires a suppressor
(blocking diode) because it is an inductive
device controlled by a dry contact.
Example 2
A DC output controls a motor starter,
contacts on the starter control a motor.
The contacts require RC networks or
varistors.
The motor requires suppressors because it
is an inductive device.
An inductive device controlled by a solid
state switching device (like the starter coil
in this example) typically does not require
a suppressor.
Example 3
An AC output controls an interposing relay,
but the circuit can be opened by dry
contacts. Relay contacts control a solenoid
coil.
The contacts require RC networks or
varistors.
The relay coil requires a suppressor because
it is an inductive device controlled by dry
contacts.
The solenoid coil also requires a suppressor
because it is an inductive device controlled
by dry contacts.
Example 4
A contact output controls a pilot light with
a built in step-down transformer.
The pilot light requires a suppressor
because its transformer is an inductive
device controlled by a dry contact.
Example 5
A contact output controls a relay that
controls a brake solenoid.
The contacts require RC networks or
varistors.
Both the relay and the brake solenoid
require suppressors because they are both
inductive devices controlled by dry
contacts.
1CR
V DC
Digital Contact Output
L1 L2
1MS
L1
1MS
1M
L2
1MS
1MS
L1
Digital DC Output
Solid-state
Switch
Suppressor
Suppressor Su
ppr
es
so
r
2L 1L
1CR
1CR
1S
Solid-state
Switch
Suppressor
Suppressor
Digital AC Output
L1 L2
Digital Contact Output
Suppressor
Pilot Light with Built-in
Step-down Transformer
1CR
115V AC 480V AC
RC 1 RC 1
Digital Contact Output
Suppressor
Suppressor
Brake Solenoid