Advanced Electical Machines

Radial and Axial Flux Permanent Magnet Machines

Permanent magnets replaced the electromagnets (which have windings and require an external energy )

The Synchronous machines, with convectional field excitation in the rotor is replaced by PM excitation ( Slip rings & Brush assembly is eliminated )

Mechanical commutator was replaced by Electronic commutator

All this contributed for the development of PMBLDC & PM SYNCHRONOUS MACHINES .

Permanent Magnet Motors

Permanent Magnet motors

Permanent Magnet motors

The inherent features of PMs, such as high efficiency, high compactness and wide operation speed range , make the machine suitable for direct drive application .

Permanent Magnet motors

Depending upon the direction through the Air gap ,PM machines are divided in to three main groups

◦ Radial Flux machine

◦ Axial Flux machine

◦ Transversal Flux machine

Classification of PM machines

Classification of PM machines

Radial

Axial

Transverse

Radial & Axial Flux

PMAC axial flux motors exist. In these motors, magnetic force (through the air gap) is along the same plane as the motor shaft — along the motor length.

Axial flux can be thought of as having the same orientation as disc brakes on a regular vehicle, as the disc rotates like the rotor in

an axial flux design. Radial flux motors are the more traditional

design, in which the magnetic force is perpendicular to the length of the motor shaft.

Radial & Axial Flux

Initially for several decades RFPM Machines have been used widely in fractional horsepower application.

But now after 2002 the era of PM machines for large scale Industrial use has begun.

PM machines have been designed for large power range for ship propulsion drive & Wind mill generators,

Even smaller power range for low speed applications.

Radial Flux Machines

The figure illustrate possible radial-flux PM machine configaration

The most commonly manufactured machine is an external stator-internal rotor machine(fig a & b ).

The structure with external rotor & internal stator, know also as drum motor, is an alternative configaration.(wheel motor of Electrical Vehicles)(fig c)

Recently a machine structure with toroidally wound internal stator and two rotors has been introduced,(fig d).

Several variations of assembling the magnets into the rotor of a radial-flux machines are possible and reasonable.

Possible rotor configurations

Possible Rotor Configuration

Possible Rotor Configuration

Axial Flux Machines In 1831 Faraday built first disc generator &

in 1889 even Tesla developed a machine . Both of this machine worked on the

principle of Axial flux principle.

The research interest about axial flux electric machine is due to special application limited geographical considerations.

Axial Flux Machines

Classification of axial flux machines Several axial-flux machine configaration can be

found regarding the stator position with respect to the rotor position and the winding arrangement.

Possible configuration areStructure with one rotor and one stator .Structure, in which the stator is located between the

rotors,Structure in which the rotor located between the

stators,Multistage structure including several rotors and

stators.

Classification of axial flux machines