Mind Map Gallery DIRECT CURRENT MOTOR
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DIRECT CURRENT MOTOR
By group OHM - Assignment for SKEE 2413 Basic Power and Electric Machine
Edited at 2021-01-29 09:11:39
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DIRECT CURRENT MOTOR
Basic Construction
Yoke
outer part called starter - made out of cast iron or cast steel
supports the field poles and field winding
provides a magnetic path to the main field flux
acts as a protecting cover for the whole machine
Field Pole
mounted inside the yoke - made of thin lamination stacked together and consist of pole cores and pole shoes
provides support to the field winding
provide slow reactance path to the main field flux
distributes the main field flux uniformly all around the periphery of the armature
Field Winding
the field coils are wound on the poles
they produce a magnetic field when D.C. is passed through them.
Armature
Armature Core
It houses the windings in the slot - made of sheet-steellaminations
provides a low reactance path to the main field flux and the armature flux
Armature Windings
is the heart of the DC motor in which the torque isdeveloped.
it produces armature flux when current is passed through them. This flux reacts with main field flux and produces rotation or torque.
Commutator
consists of copper segments tightly fastened together with mica/micaniteinsulating separators on an insulated base
it collects D.C. from brushes, converts it into A.C. and supplies to the armature windings.
Brushes
elements which are connecting the armature windings (through commutator)to the external terminal of the motor
it collects D.C. from brushes, converts it into A.C. and supplies to the armature windings.
Types
Self-Excited
Shunt
the field winding is connected in parallel with the armature
Series
the field winding is connected in series with the armature winding
Compound Excited
A DC Motor having both shunt and series field windings
Separately Excited
the field coils or field windings are energised by a separate DC source
Permanent Magnet
uses a permanent magnet to create the magnetic field required for the operation of a DC motor
Speed Control
Armature resistance control (Rheostat Control)
Variation of field flux Ф (Field flux control)
Armature Voltage control
Torque
Speed – Torque Characteristics (N v/s T)
DC Series Motor
are used where high starting torque is required like hoists, cranes, electrical locomotives, elevators etc
DC Shunt Motor
are used where constant speed and low starting torque is required like centrifugal pumps, fans, blowers, conveyers etc