Vector Control; Sensorless Control And With Encoder - WEG CFW-11 Programming Manual

11 VECTOR CONTROL

It consists in the control type based on the separation of the motor current into two components:
 Flux producing current I
 Torque producing current I
The I current is related to the motor electromagnetic flux, while the I
d
produced at the motor shaft. With this strategy one gets the so called decoupling, i.e., one can control the
motor flux and torque independently by controlling the I
Since these currents are represented by vectors that rotate at the synchronous speed, when observed from a
stationary referential, a referential transformation is done so that they are changed to the synchronous referential.
In the synchronous referential these values become DC values proportional the respective vector amplitudes.
This simplifies considerably the control circuit.
When the I vector is aligned with the motor flux, it can be said that the vector control is orientated. Therefore it
d
is necessary that the motor parameters be correctly adjusted. Some of those parameters must be programmed
with the motor nameplate data and others obtained automatically through self-tuning or from the motor data
sheet supplied by the manufacturer.
The Figure 11.2 on page 11-4
11.1 on page 11-2
measured by the inverter, will be used to obtain the correct vector orientation. In the vector with encoder control
case, the speed is obtained directly fr om the encoder signal, while in the sensorless vector control there is an
algorithm which estimates the speed, based in the output currents and voltages.
The vector control measures the current, separates the flux and torque portions and transforms these variables to
the synchronous referential. The motor control is accomplished by imposing the desired currents and comparing
them with the actual values.
It is recommended that the motor current be greater than 1/3 of the inverter rated current.

11.1 SENSORLESS CONTROL AND WITH ENCODER

The Sensorless Vector Control is recommended for the majority of the applications, because it allows the
operation in a speed variation range of 1:100, accuracy in the speed control of 0.5 % of the rated speed, high
starting torque and fast dynamic response.
Another advantage of this control type is the greater robustness against sudden line voltage and load changes,
avoiding unnecessary overcurrent trips.
The necessary settings for the good operation of the sensorless vector control are done automatically. Therefore
the used motor must be connected to the CFW-11 inverter.
(oriented with the motor electromagnetic flux).
d
(perpendicular to the motor flux vector).
q
presents the block diagram for the vector control with encoder and the
for the sensorless vector control. The information of the speed, as well as of the currents
current is directly related to the torque
q
and I currents respectively.
d q
Vector Control
Figure
11
11-1