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Selection and protection of a motor
(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
Inverter Capacity
55K or lower 75K or higher
Running frequency : 1Hz or more
Carrier frequency: 2kHz
Running frequency : 1Hz or less
Carrier frequency: 2kHz
CAUTION
⋅ Fault 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.
0
30
60
90
120
150
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
Operation time (S)
0
30
60
90
120
150
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
Operation time (S)
0
3
6
9
12
15
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
Operation time (S)
0
3
6
9
12
15
0 25 50 75 100 125 150 175 200
Ratio of the motor current
to the inverter rated current (%)
Operation time (S)