Rockwell Automation Publication 2080-UM002L-EN-E - November 2021
33
Chapter 2 About Your Controller
Master Control Relay
A hard-wired master control relay (MCR) provides a reliable means for
emergency machine shutdown. Since the master control relay allows the
placement of several emergency-stop switches in different locations, its
installation is important from a safety standpoint. Overtravel limit switches or
mushroom-head push buttons are wired in series so that when any of them
opens, the master control relay is de-energized. This removes power to input
and output device circuits.
See
Place the main power disconnect switch where operators and maintenance
personnel have quick and easy access to it. If you mount a disconnect switch
inside the controller enclosure, place the switch operating handle on the
outside of the enclosure, so that you can disconnect power without opening
the enclosure.
Whenever any of the emergency-stop switches are opened, power to input and
output devices should be removed.
When you use the master control relay to remove power from the external I/O
circuits, power continues to be provided to the controller’s power supply so
that diagnostic indicators on the processor can still be observed.
The master control relay is not a substitute for a disconnect to the controller. It
is intended for any situation where the operator must quickly de-energize I/O
devices only. When inspecting or installing terminal connections, replacing
output fuses, or working on equipment within the enclosure, use the
disconnect to shut off power to the rest of the system.
Using Emergency-Stop Switches
When using emergency-stop switches, adhere to the following points:
•
Do not program emergency-stop switches in the controller program. Any
emergency-stop switch should turn off all machine power by turning off
the master control relay.
•
Observe all applicable local codes concerning the placement and labeling
of emergency-stop switches.
•
Install emergency-stop switches and the master control relay in your
system. Make certain that relay contacts have a sufficient rating for your
application. Emergency-stop switches must be easy to reach.
WARNING:
Never alter these circuits to defeat their function since serious
injury and/or machine damage could result.
If you are using an external DC power supply, interrupt the DC output side
rather than the AC line side of the supply to avoid the additional delay of
power supply turn-off.
The AC line of the DC output power supply should be fused.
Connect a set of master control relays in series with the DC power supplying
the input and output circuits.
Do not control the master control relay with the controller. Provide the
operator with the safety of a direct connection between an emergency-stop
switch and the master control relay.
Содержание Allen-Bradley Micro850
Страница 12: ...12 Rockwell Automation Publication 2080 UM002L EN E November 2021 Preface Notes ...
Страница 36: ...36 Rockwell Automation Publication 2080 UM002L EN E November 2021 Chapter 2 About Your Controller Notes ...
Страница 44: ...44 Rockwell Automation Publication 2080 UM002L EN E November 2021 Chapter 3 Install Your Controller Notes ...
Страница 120: ...120 Rockwell Automation Publication 2080 UM002L EN E November 2021 Chapter 7 Motion Control Notes ...
Страница 156: ...156 Rockwell Automation Publication 2080 UM002L EN E November 2021 Chapter 9 Controller Security Notes ...
Страница 184: ...184 Rockwell Automation Publication 2080 UM002L EN E November 2021 Chapter 10 Using microSD Cards Notes ...
Страница 226: ...226 Rockwell Automation Publication 2080 UM002L EN E November 2021 Appendix C Quickstarts 10 Click Finish to complete ...
Страница 248: ...248 Rockwell Automation Publication 2080 UM002L EN E November 2021 Appendix C Quickstarts Notes ...
Страница 262: ...262 Rockwell Automation Publication 2080 UM002L EN E November 2021 Appendix D User Interrupts Notes ...
Страница 272: ...272 Rockwell Automation Publication 2080 UM002L EN E November 2021 Appendix E Troubleshooting Notes ...