84-14 9424200996
Settings Calculation Examples BE1-11m
=
(
5%
)
(4)
= 0.05 4 4.54 = 0.908
Equation 84-8. 50-3 Pickup
Select I2 mode, set the Pickup setting to 0.908 Secondary A, and set the Time Delay to 10 seconds as
shown in Figure 84-17.
Figure 84-17. Protection, Current, Instantaneous Overcurrent (50-3) Screen
Instantaneous Overcurrent (50-4) - Overload Protection
The 50-4 element is used for overload protection while the motor is running. This protection is configured
according to the service factor of the motor. The pickup setting should be 115 to 125 percent of the
service factor per IEEE C37.96-2000, IEEE Guide for AC Motor Protection. If the service factor is 1.0,
then overload pickup should be 115 percent of FLA. The pickup setting should be 130 percent of FLA for
a service factor of 1.15. If the service factor is unknown, use 1.0. In this example, the service factor is 1.0
and the pickup setting is calculated using Equation 84-9. Secondary full load amps is calculated in
Equation 84-1.
=
1.15 = 4.54 1.15 = 5.221
Equation 84-9. 50-4 Pickup
A delay is used to prevent the BE1-11m from operating under temporary overloads while the motor is
running. Typically, the delay is set short, but can be set longer if the process is significant or if an operator
is regulating the load. The NEMA MG-1 standard states that “a large induction motor can withstand an
occasional overload of 1.5 • FLA for 30 seconds.” A conservative time delay (using a factor of 1) is
calculated in Equation 84-10. The hot safe stall time is found in the motor manufacturer data.
= 1
(
9
)
= 9
Equation 84-10. 50-4 Time Delay
Select three-phase mode, set the Pickup setting to 5.221 Secondary A, and set the Time Delay to 9
seconds as shown in Figure 84-18.
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