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The SRM has wound field coils as in a DC motor for the stator windings. The rotor however has no magnets or coils attached. It is a solid salient-pole rotor (having projecting magnetic poles) made of soft magnetic material (often laminated steel). When power is applied to the stator windings, the rotor's magnetic reluctance creates a force that attempts to align the rotor pole with the nearest stator pole. In order to maintain rotation, an electronic control system switches on the windings of successive stator poles in sequence so that the magnetic field of the stator "leads" the rotor pole, pulling it forward. Rather than using a mechanical commutator to switch the winding current as in traditional motors, the switched-reluctance motor uses an electronic position sensor to determine the angle of the rotor shaft and solid state electronics to switch the stator windings, which enables dynamic control of pulse timing and shaping. This differs from the apparently similar induction motor that also energizes windings in a rotating phased sequence. In an SRM the rotor magnetization is static (a salient 'North' pole remains so as the motor rotates) while an induction motor has slip, and rotates at slightly less than synchronous speed. SRM's absence of slip makes it possible to know the rotor position exactly, allowing the motor to be stepped arbitrarily slowly.

Abdulaziz

Saleh

Some applications:

a) General purpose industrial drives;

b) Application-specific drives: compressors, fans, pumps, centrifuges;

c) Domestic drives: food processors, washing machines, vacuum cleaners;

d) Electric vehicle application;

e) Aircraft applications;

The switched reluctance motor (SRM) is also known as Variable Reluctance Motor drives for industrial applications are of recent origin. Since 1969, a variable reluctance motor has been proposed for variable speed applications.

SRM an attractive alternative to both AC and DC machines in adjustable-speed drives

Construction:

Variable Reluctance Motor or Switched Reluctance Motor has two different constructions: Singly Salient Construction and Doubly Salient Construction. Stator and rotor magnetic circuits are laminated to reduce the core losses in both type of SRM.

shows a one phase winding of a 4-phase switched reluctance motor having 8 poles on stator and 6 poles on rotor. While the rotor has no windings, each stator pole has a concentrated winding around it and each pair of diametrically opposite coils comprise one phase of the motor.

The rotor is also made up of silicon steel stampings with outward projected poles.

Number of poles of rotor is different from the number of poles of the stator. In most of the

available motors the number of poles of the rotor is 4 or 6 depending upon the number of stator poles 6 or 8.

In summary:

Instruction:

• • Stator and rotor are salient in structure
• • stator windings are independent concentrated windings which are excited with switches from source
• • no field windings hence singly excited
• • diametrically opposite armature windings are connected to form a phase
• • for biderctional control and self starting, num of rotor poles are less than num of stator poles

Mohammed

Operating principle..

Omar

1- The SRM also comes with a few disadvantages among

which torque ripple and acoustic noise are the most critical .

2- The higher torque ripple also causes the ripple current in the DC supply to be quite large, necessitating a large filter capacitor

3- The doubly salient structure of the SRM also causes higher acoustic noise compared with other machines

Prepared by..

4-The absence of permanent magnets imposes the burden of excitation on the stator windings and converter, which increases the converter KVA requirement. Compared with PM brushless machines, the per unit stator copper losses will be higher, reducing the efficiency and torque per ampere .

References...

• http://www.engineeringenotes.com/electrical-engineering/electric-motors/switched-reluctance-motor-construction-operation-electrical-engineering/37004

• https://electricalbaba.com/switched-reluctance-motor-construction-working/

• https://www.machinedesign.com/motorsdrives/are-switched-reluctance-motors-you

• https://people.ucalgary.ca/~aknigh/electrical_machines/other/sr.html

• https://en.wikipedia.org/wiki/Switched_reluctance_motor

5- However, the maximum speed at constant power is not limited by the fixed magnet flux as in the PM machine, and, hence, an extended constant power region of operation is possible in SRMs

Disadvantage :

Switched Reluctance Motor..

• Mohammed saeed nazer (437009490)
• Omar Ali Bajandouh (437005799)
• Mohammed Almalki (437001332)
• Abdulaziz husin ( 437003412)
• Saleh Bazaid (436040839)

section : 1

Group : C

D. Jamal Sweilem

Mohammed

• The speed of the switched reluctance rotor is determined by the switching speed of the stator poles.

• The output torque is determined by the amount of current passing through the stator windings and is proportional to the square of the current.

1- Extremely high speeds with a wide constant power region are possible .

Omar

2- The bulk of the losses appear in the stator, which is relatively easier to cool.

• The torque of the motor also depends on the angle of the rotor's poles with respect to the stator's pole, this can result in "ripple" in the output's torque if there was a small number of poles.

3- Bidirectional currents are not necessary, which facilitates the reduction of the number of power switches in certain applications.

• SR motors have higher efficiency at higher speeds, they also can run forward and backward, as a motor or generator.

4- The starting torque can be very high without the problem of excessive in-rush current due to its higher self-inductance

5- The open-circuit voltage and short-circuit current at faults are zero or very small

Characteristics of switched reluctance motors..

6- The maximum permissible rotor temperature is higher, since there are no permanent magnets

7- There is low rotor inertia and a high torque/inertia ratio

Advantage :