4.2.6 Electronic overcurrent protection (Pr. 9, Pr. 48)
Pr. 9 "electronic overcurrent protection"
Pr. 48 "second electronic overcurrent
Set the current of the electronic overcurrent protection to protect the motor from
overheat. This feature provides the optimum protective characteristics, including
reduced motor cooling capability, at low speed.
*0.1K to 0.75K are set to 85% of the rated inverter current.
y Set the rated current [A] of the motor.
y Setting "0" makes the electronic overcurrent protection (motor protective function)
invalid. (The inverter's protective function is valid.)
y When using Mitsubishi constant-torque motor, first set "1" in Pr. 71 to choose the
100% continuous torque characteristic in the low-speed range. Then, set the rated
motor current in Pr. 9.
y Pr. 48 "Second electronic overcurrent protection" is made valid when the RT signal
is on. (Note 4)
Note: 1. When two or more motors are connected to the inverter, they cannot be
protected by the electronic overcurrent protection. Install an external thermal
relay to each motor.
2. When the difference between the inverter and motor capacities is large and
the setting is small, the protective characteristics of the electronic
overcurrent protection will be deteriorated. In this case, use an external
3. A special motor cannot be protected by the electronic overcurrent protection.
Use an external thermal relay.
4. The RT signal serves as the second function selection signal and makes the
other second functions valid. Refer to page 145 for Pr. 180 to Pr. 183 (input
terminal function selection).
0 to 500A
0 to 500A, 9999
Pr. 71 "applied motor"
Pr. 180 to Pr. 183
(input terminal function
9999: Function invalid