Mitsubishi Electric FR-A720-0.4K Instruction Manual page 187

(2) Electronic thermal relay function operation characteristic (THT)
Electronic thermal relay function (transistor protection thermal) operation characteristics of the inverter when the ratio
of the motor current to the inverter rated current is presented as transverse is shown. Transverse is calculated as
follows: (motor current [A]/inverter rated current [A]) × 100 [%].
Optimum Conditions
Running frequency : 1Hz or more
Carrier frequency: 2kHz
Running frequency : 1Hz or less
Carrier frequency: 2kHz
CAUTION
⋅ Protective function by electronic thermal relay function is reset by inverter power reset and reset signal input. Avoid
unnecessary reset and power-off.
⋅ The operation time of the transistor protection thermal relay shortens when the Pr. 72 PWM frequency selection setting increases.
⋅ Since a thermal protector is built in a motor dedicated for vector control (SF-V5RU), set "0" in Pr. 9 to use the motor.
55K or less
150
120
90
60
30
0
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
15
12
9
6
3
0
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
Selection and protection of a motor
Inverter Capacity
75K or more
150
120
90
60
30
0
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
15
12
9
6
3
0
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
4
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