Application; Signals; Settings - ABB 615 series Technical Manual

1MAC059074-MB A
4.1.6.5
4.1.6.6
4.1.6.7
Table 288: 51LR Non group settings (Basic)
Parameter Values (Range)
Operation 1=enable
5=disable
Pickup value 0.10...10.00
Trip delay time 100...120000
615 series ANSI
Technical Manual

Application

The motor protection during stall is primarily needed to protect the motor from excessive
temperature rise, as the motor draws large currents during the stall phase. This condition
causes a temperature rise in the stator windings. Due to reduced speed, the temperature
also rises in the rotor. The rotor temperature rise is more critical when the motor stops.
The physical and dielectric insulations of the system deteriorate with age and the
deterioration is accelerated by the temperature increase. Insulation life is related to the
time interval during which the insulation is maintained at a given temperature.
An induction motor stalls when the load torque value exceeds the breakdown torque value,
causing the speed to decrease to zero or to some stable operating point well below the rated
speed. This occurs, for example, when the applied shaft load is suddenly increased and is
greater than the producing motor torque due to the bearing failures. This condition
develops a motor current almost equal to the value of the locked-rotor current.
51LR is designed to protect the motor in stall or mechanical jam situations during the
running state. To provide a good and reliable protection for motors in a stall situation, the
temperature effects on the motor have to be kept within the allowed limits.

Signals

Table 286: 51LR Input signals
Name Type
I_A SIGNAL
I_B SIGNAL
I_C SIGNAL
BLOCK BOOLEAN
Table 287: 51LR Output signals
Name Type
TRIP BOOLEAN

Settings

Unit Step
xIn 0.01
ms 10
Default Description
0 Phase A current
0 Phase B current
0 Phase C current
0=False Block signal for activating the blocking mode
Description
Trip
Default Description
1=enable Operation Disable / Enable
2.50 Pickup value
2000 Trip delay time
Section 4
Protection functions
287