Filter
Top Products
E-21
8) To control the torque
[Set the V/f control selection parameter at
(sensorless vector control (speed/torque switchable).]
In this mode, the torque produced by the motor is controlled by means of torque command
signals. The rotating speed of the motor is determined by the relationship between the load
torque and the torque produced by the motor.
This control mode involves the setting of the motor constant.
Basically, however, there is no need to set the motor constant if the inverter is used for
a Toshiba 4P motor with the same capacity as the inverter.
The motor constant can be set in any of the following two ways:
1) Set the extended parameter at . In this mode, the motor constant is set
automatically. (Auto-tuning) => Refer to selection 2 in 6.21 for details.
2) The constants of motors can also be set individually.
=> Refer to selection 3 in 6.21 for details.
9) Notes on the vector control
1) The vector control fully exerts its effect in frequency ranges below the base
frequency () and its effect is reduced in frequency ranges above the base
frequency.
2) Set the base frequency between 40 and 120 Hz when selecting a sensorless vector
control mode (
,
), or between 25 and 120 Hz when selecting a
sensor vector control mode (
,
).
3) Use a general-purpose or squirrel-cage motor with the same rating as the inverter,
or smaller by one rank.
This inverter cannot be used for motors with capacities of less than 0.4 kW. If the
VFA7-2004PL is combined with a 0.2 kW motor, an auto-tuning error () may
arise, and thus disable the vector control.
4) Use a motor with 2 to 16 poles.
5) Use the inverter for a single motor at a time. This inverter is incapable of vector
-controlling more than one motor simultaneously.
6) Do not use wires longer than 30 m for the connection between the inverter and the
motor. When using wires longer than 30 m, select a normal auto-tuning mode to
improve the low-speed torque characteristics in vector control mode. In this case,
the torque produced by the motor decreases more or less around the rated
frequency because of a voltage drop.
7) If a reactor or surge suppressing filter is connected between the inverter and the
motor, the torque produced by the motor may decreases or the inverter may trip
() in auto-tuning mode, and therefore the vector control can not be used.
8) Connect speed sensor for vector control with sensor to the motor. Connecting via
gear, etc. causes motor’s oscillating or inverter’s trip by lack of rigidity.
9) When is set at , or , the impressed voltage to a motor might decrease
according to the specification of a power supply.
10) To use vector control with a sensor, the option (refer to 9.5 or 9.6) is needed.