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PERMANENT MAGNET SYNCHRONOUS MOTOR The notation for PMSM is PMAC In PMSM the D.C field winding of the rotor is replaced by Permanent Magnets Permanent Magnet Materials: Alnico, Cobalt-Samarium, Ferrite. Advantages: Elimination of field copper loss. Higher power density.
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PERMANENT MAGNET SYNCHRONOUS MOTOR The notation for PMSM is PMAC In PMSM the D.C field winding of the rotor is replaced by Permanent Magnets Permanent Magnet Materials: Alnico, Cobalt-Samarium, Ferrite. Advantages: Elimination of field copper loss. Higher power density. Lower rotor inertia. More robust construction of motor. Higher efficiency. Disadvantages : Loss of flexibility of field flux control. Remagnetization effect. Higher costs. Application: Low power range motors are widely used in industries. PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVES (PMSM)
Types Permanent Magnet Synchronous motors 1.Surface Mounted-PMSM • Projecting type • Inset type 2.Interioror Buried-PMSM
Types of Permanent Magnet Synchronous motors • 1.Surface Mounted-PMSM • Projecting type • Inset type • 2.Interioror Buried-PMSM
Types of Permanent Magnet Synchronous motors Based on nature of voltage induced in the stator classified as Sinusoid ally excited PMAC: • Stator has distributed winding. • Stator induced voltage has sinusoidal waveform. Trapezoid ally excited PMAC: • Stator has concentrated winding. • Stator induced voltage has trapezoidal waveform.
Speed control of sinusoidal PMAC • The speed of the PMAC motor is controlled by feeding them from variable frequency ,voltage and current. • They are operated in self controlled mode. • In closed loop control ,current regulated VSI is used. • The inverter is operated to supply motor three phase currents of the magnitude and phase commanded by reference currents isa,isb and isc which generated by a reference current generator. • The stator current templates for the three phases are generated by the rotor position sensors in such a way that δ = π/2
Speed control of Trapezoidal PMAC • According to the torque equation torque is proportional to Id. • Regenerative braking mode operation is obtained by reversing phase currents. • This will also reverse the source current Id. • Now power flow from the machine to inverter and from inverter to dc source.