Rockwell Automation Allen-Bradley E300, User Manual

Page: 139 / 546

Rockwell Automation Publication 193-UM015D-EN-P - February 2015 139
Protective Trip and Warning Functions Chapter 6
Table 170 - Overload Time to Reset (Parameter 3)
Nonvolatile Thermal Memory
The E300 Electronic Overload Relay includes a nonvolatile circuit to provide
thermal memory. The time constant of the circuit corresponds to a Trip Class 20
setting. During normal operation, the thermal memory circuit is continuously
monitored and updated to accurately reflect the thermal capacity utilization of
the connected motor. If power is removed, the thermal memory of the circuit
decays at a rate equivalent to the cooling of a Trip Class 20 application. When the
power is re-applied, the E300 Electronic Overload Relay checks the thermal
memory circuit voltage to determine the initial value of % Thermal Capacity
Utilized (Parameter 1).
Phase Loss Protection
A high current imbalance, or phase failure, can be caused by defective contacts in
a contactor or circuit breaker, loose terminals, blown fuses, sliced wires, or faults
in the motor. When a phase failure exists, the motor can experience an additional
temperature rise or excessive mechanical vibration. This may result in a
degradation of the motor insulation or increased stress on the motor bearings.
Rapid phase loss detection helps to minimize the potential damage and loss of
production.
Phase Loss Inhibit Time
Phase Loss Inhibit Time (Parameter 239) allows you to inhibit a phase loss trip
from occurring during the motor starting sequence. It is adjustable from 0…250
seconds.
Table 171 - Phase Loss Inhibit Time (Parameter 239)
Overload Time to Reset (Parameter 3)
Default Value 0
Minimum Value 0
Maximum Value 9999
Parameter Type UINT
Size (Bytes) 2
Scaling Factor 1
Units Seconds
Phase Loss Inhibit Time (Parameter 239)
Default Value 0
Minimum Value 0
Maximum Value 250
Parameter Type USINT
Size (Bytes) 1
Scaling Factor 1
Units Seconds