5.16.1 Manual torque boost
Voltage drop in the low-frequency range can be compensated, improving reduction of the motor torque in the low-speed range.
• Motor torque in the low-frequency range can be adjusted according to the load, increasing the motor torque at the start up.
• By using the RT signal or X9 signal, it is possible to switch between 3 types of torque boost.
Second torque boost
Third torque boost
The initial value for the FR-A820-00077(0.75K) or lower and FR-A840-00038(0.75K) or lower.
The initial value for the FR-A820-00105(1.5K) to FR-A820-00250(3.7K), FR-A840-00052(1.5K) to FR-A840-00126(3.7K).
The initial values for the FR-A820-00340(5.5K), FR-A820-00490(7.5K), FR-A840-00170(5.5K), FR-A840-00250(7.5K).
The initial value for the FR-A820-00630(11K) to FR-A820-03160(55K), FR-A840-00310(11K) to FR-A840-01800(55K).
The initial value for the FR-A820-03800(75K) or higher and FR-A840-02160(75K) and higher.
Starting torque adjustment
• Assuming Pr.19 Base frequency voltage is 100%, set the output voltage at 0 Hz to Pr.0 (Pr.46, Pr.112) in percentage.
• Perform the adjustment of the parameter little by little (approximately 0.5%), and confirm the status of the motor each time.
The motor may overheat when the value is set too high. Do not use more than 10% as a guideline.
Setting multiple torque boosts (RT signal, X9 signal, Pr.46, Pr.112)
• When changing the torque boost depending on the application or when using single inverter switching between multiple
motors, use the second (third) torque boost.
• Pr.46 Second torque boost is enabled when the RT signal is ON.
• Pr.112 Third torque boost is enabled when the X9 signal is ON. Set "9" in Pr.178 to Pr.189 (Input terminal function
selection) to assign the X9 signal function to a terminal.
• The RT (X9) signal acts as the second (third) function selection signal and makes the other second (third) functions valid.
• The RT signal is assigned to terminal RT in the initial status. Set "3" in one of Pr.178 to Pr.189 (Input terminal function
selection) to assign the RT signal to another terminal.
• Set a larger value when the distance between the inverter and the motor is long or when there is not enough motor torque in
the low-speed range. It may cause overcurrent trip when it is set too large.
• Setting for Pr.0, Pr.46, and Pr.112 becomes enabled only when the V/F control is selected.
• When the initial value is set in Pr.0, the Pr.0 setting is automatically changed by changing the Pr.71 Applied motor or Pr.81
Number of motor poles setting. (Refer to
• Changing the terminal assignment using Pr.178 to Pr.189 (Input terminal function selection) may affect the other functions.
Set parameters after confirming the function of each terminal.
5.16 (G) Control parameters
0 to 30%
Set the output voltage at 0 Hz in %.
0 to 30%
Set the torque boost value at when RT signal is ON.
Without the second torque boost
0 to 30%
Set the torque boost value at when the X9 signal is ON.
Without the third torque boost