4-66
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. It also 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).
The control regulating the motor current requires some voltage margin between the voltage that the inverter can
output and the induced voltage of the motor. Usually a general-purpose motor is so designed that the voltage
matches the commercial power. Under the control, therefore, it is necessary to suppress the motor terminal
voltage to the lower level in order to secure the voltage margin required.
However, driving the motor with the motor terminal voltage suppressed to the lower level cannot generate the
rated torque even if the rated current originally specified for the motor is applied. To ensure the rated torque, it is
necessary to increase the rated current. (This also applies to vector control with speed sensor.)
This control is not available in MD-mode inverters, so do not set F42 data to "5" for those inverters.
Vector control with speed sensor
This control requires an optional PG (pulse generator) and an optional PG interface card to be mounted on a
motor shaft and an inverter, respectively. The inverter detects the motor's rotational position and speed according
to PG feedback signals and uses them for speed control. It also decomposes the motor drive current into the
exciting and torque current components, and controls each of components in vector.
It is possible to obtain the desired response by adjusting the control constants (PI constants) using the speed
regulator (PI controller).
The control enables speed control with higher accuracy and quicker response than vector control without speed
sensor.
Since slip compensation, dynamic torque control, and vector control with/without speed sensor use motor
parameters, the following conditions should be satisfied to obtain full control performance.
• A single motor should be controlled per inverter.
• Motor parameters P02, P03, P06 to P23, P55 and P56 are properly configured. Or, auto-tuning (P04) is
performed.
• Under dynamic torque control, the capacity of the motor to be controlled is two or more ratings lower
than that of the inverter; under vector control with/without speed sensor, it is the same as that of the
inverter. Otherwise, the inverter may not control the motor due to decrease of the current detection
resolution.
• The wiring distance between the inverter and motor is 164 ft (50 m) or less. If it is longer, the inverter
may not control the motor due to leakage current flowing through stray capacitance to the ground or
between wires. Especially, small capacity inverters whose rated current is small may be unable to
properly control the motor correctly even when the wiring is less than 164 ft (50 m). In that case, make
the wiring length as short as possible or use a wire with small stray capacitance (e.g., loosely-bundled
cable) to minimize the stray capacitance.
