Allen-Bradley 825-P, User Manual

Page: 100 / 266

100 Rockwell Automation Publication 825-UM004D-EN-P - November 2012
Chapter 6 Configuring Protection & Logic Functions
Logic Explanation Stop/Trip Logic
The 825-P tripping logic is designed to trip or stop motors energized through
circuit breakers or contactors. Trip relay contacts 95/96 are designed for the
purpose of being applied in motor control circuits. The relay logic lets you define
the conditions that cause a trip and the performance of the trip relay output
contacts.
Initiate Trip
The 825-P Trip Logic offers two ways to stop the protected motor:
• Trip Output Assignments.
• Serial Port or Network STOP Command.
Either of these two conditions triggers an event report. The relay controls the
Trip output contacts, depending on the relay behavior setting Trip Fail-Safe.
Assign the protection element Relay Word bits that you want to cause the relay to
trip to the Trip output (see Table 42).
Unlatch Trip
Following a fault, the trip condition is maintained until all of the following
conditions are true:
• 0.5 second minimum trip duration time passes.
• a trip reset command is received as follows:
– an Auto Reset bit from Overload, RTD, or PTC protection elements
asserts.
–
a rising edge of the Target Reset control bit (from control input, front
panel, serial port, network, or Emergency Start) is detected.
• all the motor lockout functions, described below, de-assert.
Speed 2 When the SPEED2 control input is asserted and Two Speed Enable setting is Y the
825-P selects second values for the settings. See Table 11 for a full description of
various settings.
Use the SPEED2 input for two-speed motor applications. You can also use this
input to change the settings in applications where ambient temperature varies
appreciably (e.g., exposed water pumps with different capacities during daytime
and at night).
Breaker/Contactor Auxiliary Use input if motors have an operational idling current of less than 20% FLA. Use
the auxiliary contact of motor contactor or another contact, which indicates that
the motor is switched on. The relay uses this input information to correctly
determine the Motor State (Running verses Stopped), particularly important
during periods of low idling current.
Remote Trip Use this input to trip the motor by remote protection or a control device (e.g.,
vibration switch and pressure switch).
Table 45 - Control Actions