Date Code 20010719 701 Motor Protection Relay
Settings Calculation
Basic Motor Protection
4.11
Thermal Element GENERIC Setting Method
Table 4.6 Therma l Element Configu ration Setting s, Setting Method = GE NERIC
For simple, yet thorough motor protection, you may elect to use one of the 45
available standard motor overload/locked rotor curves. Set the motor rated Full Load
Amps and Service Factor, then select the desired curve from Figure 4.2 on page 4.13.
Be sure that the standard curve you select trips in a time less than or equal to the
motor rated locked rotor time at locked rotor current. Each increase in the curve
number yields a 2.5-second increase in the curve thermal limit time at six times full
load current. For a cold motor, the curve 10 trip time at six times full load current is
25 seconds. Table 4.7 on page 4.14 and Table 4.8 on page 4.15 show the cold motor
thermal limit time versus current for several curves.
Each increase in the curve number yields a 2.1-second increase in the hot motor
thermal limit time at six times full load current.
Continue calculating the balance of thermal element settings with Thermal
Capacity Alarm Setting on page 4.21.
Table 4.6
Thermal Element Configuration
Settings, Setting Method = GENERIC
Setting Prompt Setting Range Setting Name = Example Setting
Setting Method Rating, Generic, User SETMETH = GENERIC
Full Load Amps 1.00–8.00 A
ITAP = 5 A
0.20–1.60 A
ITAP = 1 A
FLA = 5.00
FLA = 1.00
Service Factor 1.00–1.50 SF = 1.15
Curve Number 1–45 CURVE = 1
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