Rockwell Automation 1770 Industrial Automation Wiring and Grounding Guidelines User Manual
Page 11
Industrial Automation Wiring and Grounding Guidelines
11
Publication 1770-4.1 – February 1998
Connect one input directly to the L1 side of the line, on the load side
of the CRM contacts, to detect whether the CRM contacts are
closed. In the ladder logic, use this input to hold off all outputs
anytime the CRM contacts are open. (Refer to your programming
manual.) If you fail to do this, closing the CRM contacts could
generate transient emi because outputs are already turned on. To
have outputs turned on when CRM contacts are closing would be
analogous to squeezing the trigger on a hand tool as you’re plugging
it in.
Figure 8
Ungrounded ac Power-Distribution System with
Master-Control Relay
Notes:
1
2
To minimize emi generation, connect a suppressor across an inductive load. For suppressors to use, refer to 11 and C
or the Electrocube catalog.
In many applications, a second transformer provides power to the input circuits and power supplies for isolation
from the output circuits.
+ -
Output
Actuator
CRM
Back-panel
Ground Bus
FUSE
FUSE
Multiple E-stop switches
Start
CRM
CRM
GND
L1
N or L2
CRM
19240
CRM
X
1
X
2
1LT
2LT
Step-down
Transformer
2
1FU
L1
2FU
L2
3FU
L3
L1
L2
L3
Disc.
H
1
H
2
H
3
H
4
The I/O circuits form a net
inductive load switched by the
CRM contacts. Therefore, a
suppressor is needed
across the line at the load side
of the CRM contacts.
Suppressor
3
Suppressor
1
3
Connect a suppressor here to minimize emi generation from the net inductive load switched by the CRM contacts. In
some installations, a 1
m
f 220
W
suppressor (Allen-Bradley 700-N5) or 2
m
f 100
W
suppressor (Electrocube PN
RG1676-7) has been effective. For suppressors to use, refer to Figure 11 and Table C or the Electrocube catalog.
Suppressor
1
Grounding-electrode
Conductor to
Grounding-electrode
System
Equipment-
Grounding
Conductors
Controller
Power Supply
Connect when
applicable
To dc I/O
actuators/
sensors
User dc
Supply
Input
Module
Wiring
Arm
Output Module
Wiring Arm
Input
Sensor
Incoming
ac
Enclosure
Wall
To Motor
Starters