Answer Posted / sath
DC machines can be classified as self-excited, separately
excited, permanent magnet (PM), and brushless.
AC machines can be classified as induction, wound rotor,
and synchronous.
Self-excited machines can be further classified as shunt,
series, and compound. Compound machines can be further
classified as cumulative and differential. Cumulative and
differential machines can be further classified as long
shunt and short shunt. As you can see, there are a variety
of electrical configurations for a DC machine.
Induction motors can be further classified as 3-phase and
single-phase. A 3-phase induction motor can be further
classified as delta wound or wye wound. Single-phase
motors can be further classified as split phase (Fig. 3),
capacitor start, capacitor start/capacitor run, shaded
pole, repulsion start, and universal. As you can see, there
are several varieties of AC motors.
Common terms you will hear discussed with DC motors include
commutator, brushes, counter electromotive force (EMF),
torque, speed regulation, and speed-torque characteristic
curves.
Common terms you will hear discussed with AC motors include
frequency, synchronous speed, and slip.
In d.c. motor speed is depended on field strength of the
machine.
In a.c. motor speed is depended on frequency of the machine.
In d.c. motor torque is depended on armature current and
field flex.
In a.c. motor torque is depended on slip.
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