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    Special Electrical Machine

    Uploaded by

    Jesse Jones Seraspe
    Special electrical machines are electric machines designed for specialized purposes. They are classified into two categories based on how they produce torque: electromagnetically or by variable reluctance. Reluctance motors induce magnetic poles on the rotor to generate torque through magnetic reluctance. Stepper motors move in discrete steps by energizing phase coils in sequence. Permanent magnet motors are more efficient than induction motors for applications like electric vehicles since they use permanent magnets instead of field windings. Hysteresis motors are single phase motors whose rotor is made of ferromagnetic material and work based on hysteresis losses induced in the rotor.

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    Special Electrical Machine

    Uploaded by

    Jesse Jones Seraspe
    199 views15 pages
    Special electrical machines are electric machines designed for specialized purposes. They are classified into two categories based on how they produce torque: electromagnetically or by variable reluctance. Reluctance motors induce magnetic poles on the rotor to generate torque through magnetic reluctance. Stepper motors move in discrete steps by energizing phase coils in sequence. Permanent magnet motors are more efficient than induction motors for applications like electric vehicles since they use permanent magnets instead of field windings. Hysteresis motors are single phase motors whose rotor is made of ferromagnetic material and work based on hysteresis losses induced in the rotor.

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    Special electrical machines are electric machines designed for specialized purposes. They are classified into two categories based on how they produce torque: electromagnetically or by variable reluctance. Reluctance motors induce magnetic poles on the rotor to generate torque through magnetic reluctance. Stepper motors move in discrete steps by energizing phase coils in sequence. Permanent magnet motors are more efficient than induction motors for applications like electric vehicles since they use permanent magnets instead of field windings. Hysteresis motors are single phase motors whose rotor is made of ferromagnetic material and work based on hysteresis losses induced in the rotor.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    199 views15 pages

    Special Electrical Machine

    Uploaded by

    Jesse Jones Seraspe
    Special electrical machines are electric machines designed for specialized purposes. They are classified into two categories based on how they produce torque: electromagnetically or by variable reluctance. Reluctance motors induce magnetic poles on the rotor to generate torque through magnetic reluctance. Stepper motors move in discrete steps by energizing phase coils in sequence. Permanent magnet motors are more efficient than induction motors for applications like electric vehicles since they use permanent magnets instead of field windings. Hysteresis motors are single phase motors whose rotor is made of ferromagnetic material and work based on hysteresis losses induced in the rotor.

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    INTRODUCTION

    SPECIAL ELECTRICAL
    MACHINES
    Definition

    Special Electrical Machines are those machine


    which are constructionally , technically and
    functionally little different from rest of conventional
    machines.

    The concept or principle are same in both type of


    machine. However, special electric machines are
    used for special purposes.
    Special Electrical Machines Classification

     Are broadly classified into two categories on


    the basis of how they produce torque:

     Electromagnetically or
     by variable reluctance
    Torque - Electromagnetically

     Motion is produced by the interaction of two


    magnetic fields, one generated by the stator and the
    other by the rotor.

     Two magnetic fields, mutually coupled, produce an


    electromagnetic torque that tends to bring the fields
    into alignment.

     The same phenomenon causes opposite poles of bar


    magnets to attract and like poles to repel.
    Torque - Reluctance
     In the second category, motion is produced as a result
    of the variable reluctance in the air gap between the
    rotor and the stator.

     When a stator winding is energized, producing a single


    magnetic field, reluctance torque is produced by the
    tendency of the rotor to move to its minimum
    reluctance position.

     In those cases, reluctance is minimized when the


    magnet and metal come into physical contact.
    What is Reluctance ?

     Magnetic reluctance, or magnetic resistance, is a


    concept used in the analysis of magnetic circuits.

     It is analogous to resistance in an electrical circuits, but


    rather than dissipating electric energy it stores
    magnetic energy.

     In likeness to the way an electric field causes an electric


    current to follow the path of least resistance,
    a magnetic field causes magnetic flux to follow the
    path of least magnetic reluctance.
    Special Electrical Machines
    Reluctance Motor

    A reluctance motor is a type of electric


    motor that induces non-permanent magnetic
    poles on the ferromagnetic rotor. Torque is
    generated through the phenomenon
    of magnetic reluctance.
    Advantages of Reluctance Motor

    Reluctance motors can deliver very high


    power density at low cost, making them ideal
    for many applications. Some of these are:

     Washing machines
     Control rod drive mechanisms of nuclear
    reactors
    Disadvantages of Reluctance Motor

     Disadvantages are high torque ripple (the difference


    between maximum and minimum torque during one
    revolution) when operated at low speed

     Noise caused by torque ripple


    Stepper Motors

     Stepper motors are DC motors that move in


    discrete steps. They have multiple coils that
    are organized in groups called "phases". By
    energizing each phase in sequence, the
    motor will rotate, one step at a time.
    Stepper Motors

     With a computer controlled stepping you can achieve


    very precise positioning and/or speed control. For this
    reason, stepper motors are the motor of choice for
    many precision motion control applications.
     Stepper motors come in many different sizes and
    styles and electrical characteristics.  
    Permanent Magnet Motors

     A permanent magnet motor is a type of


    brushless electric motor that uses permanent
    magnets rather than winding in the field.

     Permanent magnet motors are more efficient than


    induction motor or motors with field windings for certain
    high-efficiency applications such as electric vehicles.

     Permanent magnet motors rely on neodymium.


    Hysteresis Motors

     Hysteresis motor is defined as a synchronous


    motor that is having cylindrical rotor and works on
    hysteresis losses induced in the rotor of hardened
    steel with high retentivity.

     It is a single phase motor and its rotor is made of


    ferromagnetic material with non magnetic support
    over the shaft.
    Hysteresis Motors Applications

    They are widely used in:


     Sound producing equipments
     Sound recording instruments
     High quality record players
     Timing devices
     Electric clocks
     Teleprinters

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