This document discusses special electrical machines, specifically permanent magnet synchronous motors (PMSM). It describes PMSM as a brushless DC motor with permanent magnets on the rotor that create magnetic poles instead of a field winding. The document outlines the basic construction and working principle of PMSM, noting that a rotating magnetic field from the stator interacts with the permanent rotor magnets to produce torque. Applications mentioned include servo drives, robotics, traction systems, and railway transportation.

1. Special electrical machines
Prepared by,
A.Johny Renoald M. E., Ph.D.,

2. Electrical machine
• A electrical machine consumes electrical energy to do
a specific work or it convert electrical energy to other
forms like mechanical energy, light energy, heat etc.,

3. Special Electrical Machines Types
Permanent Magnet DC Motor
1. PM synchronous motor
2. PM brushless DC motor
Reluctance motors
1. Synchronous reluctance
2. Switched Reluctance
Stepping motors
1. Single stack multi-machine
2. Multi stack multi-machine

5. Permanent magnet DC Motors

14. PMSM
• Depending on how magnets are attached to the
rotor, PMSM motors can be classified into
• Two types: Surface PMSM (SPMSM) and
interior PMSM (IPMSM).
• Permanent Magnet Synchronous Motor,
PMSM is a kind of synchronous motor in
which permanent magnet is used as rotor to
create field poles. No field winding is wound
on the rotor.

15. • Advent of Switching power
transistor and SCR in 1950’s
replaced the mechanical
commutator with electrical
commutator in the form of
inverter.
PMSM

16. • The main advantage when
compared with the conventional
synchronous machine is the
elimination of the field coil, dc
supply, and slip rings; hence, lower
loss and a less complex motor.
PMSM

17. INTRODUCTION
A permanent magnet synchronous motor is also called as
brushless permanent magnet sine wave motor. A sine
wave motor has a
1. Sinusoidal or quasi-sinusoidal distribution of magnetic
flux in the air gap.
2. Sinusoidal or quasi-sinusoidal current wave forms.
3. Quasi-sinusoidal distribution of stator conductors (i.e.)
short-pitched and distributed or concentric stator
windings.

19. Construction
• The basic construction of PMSM is same as that of
synchronous motor. The only difference lies with the
rotor. Unlike synchronous motor, there is no filed
winding on the rotor of PMSM. Field poles are
created by using permanent magnet. These Permanent
magnets are made up of high permeability and high
coercivity materials like Samarium-Cobalt and
Neodium-Iron-Boron. Neodium-Iron-Boron is mostly
used due to its ease of availability and cost
effectiveness. Theses permanent magnets are
mounted on the rotor core.

20. Working principle
• The working principle of permanent magnet synchronous
motor is same as that of synchronous motor. When three phase
winding of stator is energized from 3 phase supply, rotating
magnetic field is set up in the air gap. At synchronous speed,
the rotor field poles locks with the rotating magnetic field to
produce torque and hence rotor continues to rotate.
• As we know that synchronous motors are not self starting,
PMSM needs to be started somehow. Since there is no winding
on the rotor, induction windings for starting is not applicable
for such motors and therefore variable frequency power supply
for this purpose.

21. Application:
Permanent Magnet Synchronous Motor can be used as an
alternative for servo drives. It is widely used in various
industrial application viz. robotics, traction, aerospace etc.

22. EMF and Torque equation

23. Torque equation in PMSM

31. PMSM phasor diagram

32. Power controllers

34. Application in railway traction