Post on 08-Apr-2017
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MAGMOPERMANENT MAGNET DC MOTOR
Working principal of DC motor
Construction of PMDC motor
Rotor or armature of PMDC motor
A current carrying conductor is placed inside a magnetic field, there will be mechanical force experienced by that conductorWhen permanent magnet is used to create magnetic field in a DC motor, the motor is referred as permanent magnet DC motor or PMDC motorINTRODUCTIONA DC motor in simple words is a device that converts direct current(electrical energy) into mechanical energy.
PMDC are best solutions to motion control and power transmission applications where compact size, wide operating speed range, ability to adapt to a range of power sources or the safety considerations of low voltage are importantMotivation to choose this topicConveyorsElectric ChairsDoor openers
Magnets are mounted in periphery of this cylinder. The stator also serves as low reluctance return path for magnetic field.
Sometimes field coil is used in PMDC motor because if permanent magnet lose their strength, these lost strengths can be compensated by field excitation through these field coilsSTATOR
made of number of varnish insulated, slotted circular lamination of steel sheets
Varnish insulated are used to reduce eddy current lossROTOR(ARMATURE)
Similar to DC motor
Consists of core, windings, and commutator
A stator and an armature
N pole and S pole of each magnet are alternatively faced towards armature
Cylindrical stator serves as low reluctance return path for the magnetic flux
Permanent magnets lose their strength, these lost magnetic strengths can be compensated by field excitation through these field coils
Working principal of PMDC motorA DC motor in simple words is a device that converts direct current(electrical energy) into mechanical energy.
FLEMINGS LEFT HAND RULE Flemings left hand rule says that if we extend the index finger, middle finger and thumb of our left hand in such a way that the current carrying conductor is placed in a magnetic field (represented by the index finger) is perpendicular to the direction of current (represented by the middle finger), then the conductor experiences a force in the direction (represented by the thumb) mutually perpendicular to both the direction of field and the current in the conductor.
The working principal of PMDC motor is same as the working principal of DC motor
Direction of this force is governed by Flemings left hand ruleeach conductor of the armature experiences the mechanical force F=BIL
When a carrying conductor comes inside a magnetic field, a mechanical force will be experienced by the conductor
Each conductor of the armature experiences a force and the compilation of those forces produces a torque, which tends to rotate the armature.
For smaller ratings, use of permanent magnets reduces manufacturing cost.
No need of field excitation winding, hence construction is simpler.
No need of electrical supply for field excitation, hence PMDC motor is relatively more efficient.
Relatively smaller in size
Cheap in cost
The permanent magnets supply the surrounding field flux, eliminating the need for external field current. This design yields a smaller, lighter, and energy efficient motor.
Since the stator in PMDC motor consists of permanent magnets, it is not possible to add extra ampere-turns to reducearmature reaction. Thus armature reaction is more in PMDC motors.
Stator side field control, forcontrolling speed of the motor, is not possible in permanent magnet dc motors.
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