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The PM Synchronous motor is a rotating electric machine where the
stator is a classic three phase stator like that of an induction
motor and the rotor has surface-mounted permanent magnets. In this
respect, the PM Synchronous motor is equivalent to an induction
motor where the air gap magnetic field is produced by a permanent
magnet. The use of a permanent magnet to generate a substantial
air gap magnetic flux makes it possible to design highly efficient
PM motors.
A PM Synchronous motor is driven by sine wave voltage coupled with
the given rotor position. The generated stator flux together with
the rotor flux, which is generated by a rotor magnet, defines the
torque, and thus speed, of the motor. The sine wave voltage output
have to be applied to the 3-phase winding system in a way that angle
between the stator flux and the rotor flux is kept close to 90°
to get the maximum generated torque. To meet this criterion, the
motor requires electronic control for proper operation.
For a common 3-phase PM Synchronous motor, a standard 3-phase power
stage is used. The same power stage is used for AC induction and
BLDC motors. The power stage utilizes six power transistors with
independent switching. The power transistors are switched in the
complementary mode. The sine wave output is generated using a PWM
technique. |
