4.1 Test Run
4-5
Chapter 4 OPERATION
Dynamic torque vector control
To get the maximal torque out of a motor, this control calculates the motor torque for the load applied and
uses it to optimize the voltage and current vector output.
Selecting the dynamic torque vector control automatically enables the auto-torque boost and slip
compensation.
This control is effective for improving the system response to external disturbances such as load fluctuation,
and the motor speed control accuracy.
Note that the inverter may not respond to a rapid load fluctuation since this control is an open-loop V/f
control that does not perform the current control, unlike the vector control. The advantages of this control
include larger maximum torque per output current than that the vector control.
V/f control with speed sensor
Applying any load to an induction motor causes a rotational slip due to the motor characteristics, decreasing
the motor rotation. V/f control with speed sensor detects the motor rotation speed by an encoder attached
on the motor shaft and compensates the slip frequency by PI control to adjust the motor rotation to the
specified speed, improving the motor speed control precision.
Dynamic torque vector control with speed sensor
In contrast to V/f control with speed sensor, to get the maximal torque out of a motor, this control calculates
the motor torque for the load applied and uses it to optimize the voltage and current vector output. This
control is effective for improving the system response to external disturbances such as load fluctuation, and
the motor speed control accuracy.
Vector control without speed sensor
This control estimates the motor speed based on the inverter's output voltage and current to use the
estimated speed for speed control. In addition, it decomposes the motor drive current into the exciting and
torque current components, and controls each of those components in vector. No PG (pulse generator)
interface card is required. It is possible to obtain the desired response by adjusting the control constants (PI
constants) using the speed regulator (PI controller).
Since this control controls the motor current, it is necessary to secure some voltage margin between the
voltage that the inverter can output and the induced voltage of the motor, by keeping the former lower than
the latter. Usually the voltage of the general-purpose motor has been adjusted to match the commercial
power, however, in order to secure the voltage margin, it is necessary to keep the motor terminal voltage
low. If the motor is driven under this control with the motor terminal voltage being low, the rated torque
cannot be obtained even when the rated current originally specified for the motor is applied. To secure the
rated torque, therefore, it is necessary to use a motor with higher rated current. (This also applies to the
vector control with speed sensor.)
This control is not available for MD-mode inverters, so do not set F42 data to "5" for those inverters.
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