5.3 Description of Function Codes 5.3.1 F codes (Fundamental functions)
Thermal time constant (F12)
F12 sets thermal time constant of the motor. For overload detection level that is set by F11, set the electronic thermal
operation time when 150 % of current is flowing continuously. Thermal time constant of general-purpose motor of
Fuji Electric and general motors is 5 minutes for 22 kW or lower, and 10 minutes (factory default state) for 30kW or
higher.
• Data setting range: 0.5 to 75.0 (min)
(Example) When the data of function code F12 is set to “5” (5 minutes).
As shown in the figure below, when 150 % of current of operation level that was set flows for 5 minutes, motor
overload (alarm 0l1) protection function will operate. In addition, with 120 %, it operates after 12.5 minutes.
The time when alarm actually occurs is shorter than the set data because the time until the current reaches 150 %
level after exceeding the continuous allowance current (100 %) is considered.
Fig. Example of current-operation time characteristics
(Output current / Detection level current) x 100 (%)
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