ABB RELION 620 Series Technical Manual page 767

1MRS757644 F
620 series
Technical Manual
The module also measures the time START_TIME required by the motor to attain the
rated speed and the relative thermal stress IIT_RL. The values are available in the
Monitored data view.
The activation of the BLOCK input signal resets the thermal stress calculator and
deactivates the OPR_IIT output.
Stall protection
This module is activated only when the selected Operation mode setting value is "IIt
& stall" or "IIt & stall, CB".
The start-up current is specific to each motor and depends on the start-up method used,
such as direct online, autotransformer and rotor resistance insertion. The start-up time
is dependent on the load connected to the motor.
Based on the motor characteristics supplied by the manufacturer, this module is
required if the stalling time is shorter than or too close to the starting time. In such
cases, a speed switch must be used to indicate whether a motor is accelerating during
start-up or not.
At motor standstill, the STALL_IND input is active. It indicates that the rotor is not
rotating. When the motor is started, at certain revolution the deactivation of the
STALL_IND by the speed switch indicates that the rotor is rotating. If the input is not
deactivated within Lock rotor time, the OPR_STALL output is activated.
The module calculates the duration of the motor in stalling condition, the STALL_RL
output indicating the percent ratio of the start situation and the set value of Lock rotor
time. The value is available in the Monitored data view.
The activation of the BLOCK input signal resets the operation time and deactivates the
OPR_STALL output.
Cumulative start-up protection
This module protects the motor from an excessive number of start-ups.
Whenever the motor is started, the latest value of START_TIME is added to the
existing value of T_ST_CNT and the updated cumulative start-up time is available at
T_ST_CNT. If the value of T_ST_CNT is greater than the value of Cumulative time
Lim, the LOCK_START output is activated and lockout condition for the restart of
motor is enabled during the time the output is active. The LOCK_START output
remains high until the T_ST_CNT value reduces to a value less than the value of
Cumulative time Lim. The start time counter reduces at the rate of the value of Counter
Red rate.
The LOCK_START output becomes activated at the start of MOT_START. The output
remains active for a period of Restart inhibit time.
Section 4
Protection functions
761