2. 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.
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
3. Types Permanent Magnet Synchronous
motors
1.Surface Mounted-PMSM
Projecting type
Inset type
2.Interioror Buried-PMSM
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
4. 1.Surface Mounted-PMSM
Projecting type
Inset type
2.Interioror Buried-PMSM
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
5. 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.
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
6. 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
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
7. Speed control of sinusoidal PMAC
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
9. Trapezoid ally excited PMAC
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
10. 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.
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
11. Speed control of Trapezoidal PMAC
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
13. BLDC vs. PMSM
BLDC
Synchronous machine
Fed with direct currents
Trapezoidal BEMF
Stator Flux position commutation
each 60 degrees
Only two phases ON at the same time
Torque ripple at commutations
PMSM
Synchronous machine
Fed with sinusoidal currents
Sinusoidal BEMF
Continuous stator flux position
variation
Possible to have three phases ON at
the same time
No torque ripple at commutations
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
14. Conclusion
Synchronous motors use magnetic interaction to convert
electrical energy to mechanical.
Rotor must be synchronized with the rotating stator
magnetic field in order to produce torque
Pole pair numbers and excitation frequency determine the
mechanical rotation speed
Synchronous motors are classified in two categories: BLDC
and PMSM
Each type require an appropriate control
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor
15. REFERENCES
S.No Books / Web Sources
1. K.Venkataratnam, ‘Special Electrical Machines’, Universities Press (India) Private Limited, 2008
2. T.J.E. Miller, ‘Brushless Permanent Magnet and Reluctance Motor Drives’, Clarendon Press,Oxford, 1989.
3. T. Kenjo, ‘Stepping Motors and Their Microprocessor Controls’, Clarendon Press London, 1984.
4.
R.Krishnan, ‘Switched Reluctance Motor Drives – Modeling, Simulation, Analysis, Design andApplication’, CRC
Press, New York, 2001.
5. P.P. Aearnley, ‘Stepping Motors – A Guide to Motor Theory and Practice’, Peter Perengrinus ,London, 1982.
6. T. Kenjo and S. Nagamori, ‘Permanent Magnet and Brushless DC Motors’, Clarendon Press, London, 1988.
7. K.Dhayalini, “Special Electrical Machines,” Anuradha Publications, 2017.
8.
Google , Wikipedia and https://cnx.org/resources/.../PMSM_control.
Kongunadu College of Engineering & Technology Permanent Magnet Synchronous Motor