Rockwell Automation 825-P Modular Protection System for Motors User Manual - Manual (Page 101)

Rockwell Automation Publication 825-UM004D-EN-P - November 2012 101
Configuring Protection & Logic Functions Chapter 6
The relay automatically locks out the trip relay by asserting the trip signal under
any of the following start-inhibiting conditions:
• Restart (Anti-backspin) Block
The restart block timer has not expired since the motor trip occurred. The
trip condition is maintained until the timer expires.
• Minimum Time Between Starts Lockout
A new start is not permitted until after the minimum time between starts
has passed. The trip condition is maintained until a start is permitted.
• Starts-Per-Hour Limit Lockout
If the starts-per-hour limit has been met, a new start is not permitted until
60 minutes after the oldest start. The trip condition is maintained until a
start is permitted.
• TCU Start Inhibit
The motor thermal element % Thermal Capacity value is too high to
permit a normal motor start without tripping. The trip condition is
maintained until the % Thermal Capacity decreases to a level where a start
can safely take place.
If any of the above protection functions is not enabled by the relay settings, that
function does not affect trip unlatch.
Also note that the relay automatically asserts the trip signal if the motor stops and
a lockout condition is true. The trip signal is maintained until all the enabled
motor lockout conditions are satisfied.
Trips initiated by the serial port command or by network operation are
maintained for at least 0.5 second.
Start & Emergency Restart Logic
If the Trip output contact is not asserted, the relay asserts the START Relay Word
bit in response to any of the following conditions:
• the Emergency Restart Relay Word bit asserts.
• you execute the STR serial port command or a DeviceNet Start Motor
control command.
The START Relay Word bit remains asserted for 0.5 seconds, unless the relay
trips. If the relay trips before the 0.5 second timer expires, the relay resets the
timer, clearing the START Relay Word bit.
In an emergency, it could be necessary to quickly start the motor even though
a protection lockout condition exists and is holding the Trip output contact
asserted. The lockout might be a result of the thermal element or another
protection function. You can override all of the lockout conditions using the
Emergency Restart function.