dc motor


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DC motors:

DC motors Presented by:-Er. Princejit Singh

DC Motors Parts :

DC Motors Parts Magnetic Frame or Yoke Field coils Pole shoes Armature core Armature windinds Commutator Brushes and bearing

Cut section diagram:

Cut section diagram


Yoke It is the outer most part of m/c


Commutator The function of the commutator is to facilitate collection of current from the armature conductors. it rectified i.e. converts the alternating current induced in the armature conductors into unidirectional current in the external load circuit


Brushes The brushes whose function is to collect current from commutator, are usually made of carbon or graphite and are in the shape of a rectangular block. These brushes are housed in brush-holders usually of the box-type variety. As shown in Fig


Bearing Because of their reliability, ball-bearings are frequently employed, though for heavy duties, roller bearings are preferable.



Motor Principle:

Motor Principle An Electric motor is a machine which converts electric energy into mechanical energy. Its action is based on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Fleming’s Left-hand Rule and whose magnitude is given by F = BIl Newton

Generator E.M.F Equation :

Generator E.M.F Equation Let Φ = flux/pole in weber Z = total number of armture conductors = No.of slots x No.of conductors/slot P = No.of generator poles A = No.of parallel paths in armature N = armature rotation in revolutions per minute (r.p.m) E = e.m.f induced in any parallel path in armature Generated e.m.f Eg = e.m.f generated in any one of the parallel paths i.e E. Average e.m.f geneated /conductor = dΦ/dt volt (n=1) Now, flux cut/conductor in one revolution dΦ = ΦP Wb No.of revolutions/second = N/60 Time for one revolution, dt = 60/N second Hence, according to Faraday's Laws of Electroagnetic Induction, E.M.F generated/conductor is

No.of parallel paths = A No.of conductors (in series) in one path = Z/A So, In general generated e.m.f :

No.of parallel paths = A No.of conductors (in series) in one path = Z/A So, In general generated e.m.f

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