ABB eVM1 Installation And Service Instructions Manual page 79

14.7.3.1.1 Operation criteria
If the measured RMS current exceeds the motor starting setting threshold value (Start Value, Is)
for at least one phase, the protection function is started.
The protection function will remain in START status until there is at least one phase started. It will
return to passive status and the start signal will be cleared if the current falls below 95% of the
setting threshold value for all the phases.
After the protection has entered the start status and the preset operating time (Time tbr) has
elapsed, function goes into TRIP status and the trip signal is generated.
The protection function will exit the TRIP status, the trip signal and the counter will be cleared
when the measured current value for all the phases falls below 40% of the setting threshold value.
BLOCK
The Blocked Rotor protection function can be blocked to avoid operation during the normal starting
phase of the motor. The blocking input can be provided by a speed switch, i.e. by an external signal
on a digital input configured as an Interlocking Input, or by an internal logical signal as the start
signal from the Motor Start protection function.
A tachometer generator or a speed switch is used to send a defined signal at a specified speed.
If the rotor of the monitored motor is blocked, the missing speed signal will ensure that the
overcurrent function in the protective function continues to remain active.
14.7.3.2. Thermal Overload Protection
In motor protection applications, the thermal overload protection is one of the key functions for
monitoring the admissible motor temperatures with regard to potential operational overloading. In
compliance with the applicable national and international standards, the Thermal Overload
protection provides the motor thermal image with full memory function.
The Thermal Overload protection function estimates the instantaneous motor temperature (T)
value, based on motor phase current measurement, which is compared with the user-defined
thresholds.
The protection provides a warning and a tripping output, generated when the Twarn and Ttrip
user-defined thresholds are exceeded.
The protection function also prevents reconnection of overheated machines until the estimated
motor temperature has fallen below the warning threshold.
The user can configure a reset temperature (Trst) to be used as estimated motor temperature
after temperature reset from the Configuration Tool (in Monitoring window).
77