9424200996 84-15
BE1-11m Settings Calculation Examples
Figure 84-18. Protection, Current, Instantaneous Overcurrent (50-4) Screen
Instantaneous Overcurrent (50-5) - Jam Protection
The 50-5 element is used for jam protection while the motor is running. It protects the motor when the
load torque exceeds the torque capacity of the motor. This condition develops motor current equal to or
approaching locked-rotor current, and a reduction in terminal voltage depending upon the motor
impedance. The motor can be removed from service faster when using the 50-5 element instead of the
49TC element for jam protection. This results in less heating of the motor allowing it to be returned to
service faster after the cause of the stall has been corrected. The maximum stall time is listed on the
motor nameplate per the NEMA MG-1 standard. In this example, the pickup setting is calculated as 70
percent of LRC as shown in Equation 84-11. The LRC is found in the motor manufacturer data.
Secondary full load amps is calculated in Equation 84-1.
= 70% = 0.7
= 0.7 6 4.54 = 27.24
Equation 84-11. 50-5 Pickup
Select three-phase mode and set the Pickup setting to 27.24 Secondary A as shown in Figure 84-19.
Figure 84-19. Protection, Current, Instantaneous Overcurrent (50-5) Screen
Current Differential (87)
BE1-11m Motor Protection Systems with a style number of xxxxxxxxPxxxxx are equipped with differential
protection. Differential protection is preferred on all motors, but not all motors are built with access to both
ends of the motor windings. In this case, differential protection cannot be used.
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