PCB Piezotronics IMI SENSORS 686 Series Installation And Operating Manual page 26

Automatic Machinery Shutdown of Three-Phase Electrical Motor Based on a N.O. Solid State Relay
Figure 24 – Automatic Machinery Shutdown of 3-Phase Electrical Motor Based on a N.O. Solid State Relay
The Smart Switch is hooked up to provide automatic motor shutdown when the alarm threshold level is exceeded
using a normally open three channel solid state relay. Since the Smart Switch is normally closed, closing the
Start Switch will energize the solid state relay. This will cause the RL1, RL2, and RL3 contacts to close and start
the motor. If the start-up delay option for the switch is enabled, the switch will not trip regardless of the vibration
level during the specified delay time. After this delay, if the vibration level exceeds the alarm threshold, it will be
activated, thereby opening its contacts and de-energizing the solid state relay input. This will open the RL1, RL2,
& RL3 contacts and shut down the motor. Since the LA (latching) option is specified, the solid state relay input
will be constantly de-energized after this event; even if the vibration level drops below the alarm threshold value
after shutdown. The Reset pushbutton should be pushed to reset the switch and close the RL1, RL2, & RL3
contacts before restarting the motor. This will start the motor immediately without using the Start pushbutton.
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