WEG CFW-11 Series, Руководство по программированию, Страница: 289 / 307

21-1
21
PM Vector Control
21 PM VECTOR CONTROL
21.1 PERMANENT MAGNET SYNCHRONOUS MOTORS (PMSM)
Permanent magnet synchronous motors are alternating current motors with three-phase stator winding, similar
to the induction motor, and permanent magnet rotor. PMSM for industrial applications have sinusoidal CEMF
and feeding current, so that the developed torque is smooth. The CFW-11 is prepared to drive Wmagnet line
motors, which present a salient pole construction (interior magnets).
Flat pole motors (surface magnets) and motors from other manufactures can be used upon consultation.
Main characteristics of the Wmagnet motor line:

Lq inductance bigger than the Ld, because of the rotor saliencies that generate the reluctance torque.

Field weakening range: broad ([1…2] x the nominal speed).

More protection of the magnets against centrifugal force.

Higher efficiency than the induction motor (it does not present RI
2
losses in the rotor, which allows higher
temperature rise, less volume and less weight. If compared to an equivalent induction motor, the Wmagnet
motor volume can be up to 47 % less, resulting in a high volume/torque ratio, and a reduction of 36 % in the
weight. For an identical torque/power ratio, by reducing the frame size the ventilation system is also reduced.
The Wmagnet motors can be used where speed variation with constant torque and high efficiency are required,
for instance with compressors, exhausting fans, pumps and conveyors. They can also be used in lifts, where the
precise control at low speeds, smooth torque, low vibration and low noise levels, are fundamental.
21.2 SENSORLESS PM CONTROL AND PM WITH ENCODER
The vector control developed for driving the Wmagnet motor line has a structure very similar to the one used
for the induction motors. Refer to the
Figure 21.1 on page 21-2 and Figure 21.2 on page 21-3 .
In the constant torque region, the control determines the current reference id suitable for the specified motor. Therefore,
the reluctance torque is added to the torque produced by the magnets and the motor accelerates with the maximum
N.m/A ratio and fast dynamic response. Above the nominal speed, the control applies field weakening through the
control of the armature reaction, so that the motor accelerates with nominal voltage and constant power.