Rockwell Automation 193-EC1_2_3_5, 193-ECPM,592-EC1_2_3_5 E3 and E3 Plus Solid-State Overload Relay User Manual - Manual (Page 51)

Rockwell Automation Publication 193-UM002I-EN-P - December 2011 51
Protective Trip & Warning Functions Chapter 3
Overload Diagnostics
Time to Trip
When the measured motor current exceeds the trip rating of the E3 Overload
Relay, the Time to Trip, Parameter 12, indicates the estimated time remaining
before an overload trip occurs. When the measured current is below the trip
rating, the Time to Trip value is reported as 9,999 seconds.
Time To Reset
After an overload trip, the E3 Overload Relay will report the time remaining until
the device can be reset through Time to Reset, Parameter 13. Once the % Therm
Utilized value falls to or below the OL Reset Level, the Time to Reset value will
indicate zero until the overload trip is reset. After an overload trip is reset, the
Time to Reset value is reported as 9,999 seconds.
Non-Volatile Thermal Memory
The E3 Overload Relay includes a non-volatile circuit to provide thermal
memory. The time constant of the circuit corresponds to a Trip Class 30 setting.
During normal operation, the thermal memory circuit is continually monitored
and updated to accurately reflect the thermal 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 30 application. When the power is re-applied, the
E3 Overload Relay checks the thermal memory circuit voltage to determine the
initial value of % Therm Utilized,
Parameter 9.
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 Trip
The E3 Overload Relay will trip with a phase loss indication if:
• no trip currently exists,
• Phase Loss Protection is enabled,
• PL Inhibit Time has expired, and