Permanent Magnet DC Motor Construction, Working and Applications

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Permanent Magnet DC (PMDC) Motors

Basic configuration of a permanent magnet DC motor is very similar to that of a normal DC motor. The working principle of any DC motor is same, i.e. when a current carrying conductor is placed in a magnetic field, it experiences a force. A permanent magnet DC motor also works on the same principle.

PMDC Motor at Rs 2580/piece | Permanent Magnet Dc Motor, Permanent Magnet  Direct Current Motor, पीएमडीसी मोटर - Powertek Equipment Company, Mumbai |  ID: 4394461855

Construction Of Permanent Magnet DC Motor

In a PMDC motor, permanent magnets (located in stator) provide magnetic field, instead of stator winding. The stator is usually made from steel in cylindrical form. Permanent magnets are usually made from rare earth materials or neodymium.
The rotor is slotted armature which carries armature winding. Rotor is made from layers of laminated silicon steel to reduce eddy current losses. Ends of armature winding are connected to commutator segments on which the brushes rest. Commutator is made from copper and brushes are usually made from carbon or graphite. DC supply is applied across these brushes. The commutator is in segmented form to achieve unidirectional torque. The reversal of direction can be easily achieved by reversing polarity of the applied voltage.
Permanent magnet DC (PMDC) motors | electricaleasy.com

Characteristics of PMDC motors

Characteristics of PMDC motors are similar to the characteristics of dc shunt motor in terms of torque, speed and armature current. However, speed-torque characteristics are more linear and predictable in PMDC motors.

PMDC Motor : Construction, Circuit Diagram, Characteristics & Applications

Applications Of Permanent Magnet DC Motors

  • These motors are in several applications varying from fractions to numerous horsepower. These are designed with 200 kW to use in various industries.
  • These are applicable in automobiles for operating windshield wipers as well as washers, to move up the lower windows, to drive blowers for air conditioners as well as heaters.
  • These are used in computer drives, toy industries.
  • These motors are applicable in food mixers, electric toothbrushes, and moveable vacuum cleaners,.
  • These are used in a handy electric tool like hedge trimmers, drilling machines, etc.

Advantages Of Permanent Magnet DC Motors

  1. For smaller ratings, use of permanent magnets reduces manufacturing cost.
  2. No need of field excitation winding, hence construction is simpler.
  3. No need of electrical supply for field excitation, hence PMDC motor is relatively more efficient.
  4. Relatively smaller in size
  5. Cheap in cost

Disadvantages Of Permanent Magnet DC Motors

  1. The armature reaction of DC motor cannot be compensated hence the magnetic strength of the field may get weak due to the demagnetizing effect of the armature reaction.
  2. There is a chance of getting the poles permanently demagnetized (partial) due to excessive armature current during the starting, reversal, and overloading conditions of the motor.
  3. The field in the air gap is fixed and limited – it cannot be controlled externally. This makes it difficult for this type of motor to achieve efficient speed control of DC motor in this type of motor is difficult.
READ HERE  Losses In A DC Generator And DC Motor

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