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MODULE -III
Universal Motor
Universal motor runs on either a DC supply or a single phase AC supply.
The construction of this motor is similar to DC series motor in which the stator field
windings are wound in series with armature windings.
When the universal motor is fed with a DC supply, it works as a DC series motor.
When current flows in the field winding, it produces an electromagnetic
field. The same current also flows from the armature conductors. When a
current carrying conductor is placed in an electromagnetic field, it
experiences a mechanical force. Due to this mechanical force, or torque,
the rotor starts to rotate. The direction of this force is given by Fleming's
left hand rule.
When fed with AC supply, it still produces unidirectional torque because, armature
winding and field winding are connected in series, they are in same phase.
Hence, as polarity of AC changes periodically, the direction of current in armature and
field winding reverses at the same time.
Direction of magnetic field and the direction of armature current reverses in such a way
that the direction of force experienced by armature conductors remains same.
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Regardless of AC or DC supply, this implies that an universal motor works on the same
principle that a DC series motor works.
Advantages:
High starting torque
Light weight
Compact
Runs at high speed
Applications:
In hair dryers
In grinders
In table fans
Blowers
Vaccum cleaners
Stepper Motor
A stepper motor is a brushless DC motor whose rotor rotates in discrete angular
increments, when its stator windings are energized in a programmed manner.
The rotor of this motor doesnt have any electrical winding, but has salient poles.
The rotor rotates by the magnetic interaction between rotor poles and poles of
sequentially energized stator windings.
Types
There are three types of stepper motor:
Permanent Magnet stepper motor
Variable reluctance stepper motor
Hybrid synchronous stepper motor
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Stepper Motor Working:
Unlike DC motors which rotates as soon as DC voltage is applied, stepper motors rotates
according to the pattern of energizing the stator electromagnets.
The electromagnets are energized by an external control circuit, for example, a
microcontroller.
To make the motor shaft turn, first one electromagnet is given power, which makes the
gear’s teeth magnetically attracted to the electromagnet’s teeth.
So when the next electromagnet is turned ON and the first is turned OFF, the gear rotates
slightly to align with the next one and from there the process is repeated.
Each of those slight rotations is called a step, with an integer number of steps making a
full rotation

Unformatted Attachment Preview

1 MODULE -III Universal Motor ▪ Universal motor runs on either a DC supply or a single phase AC supply. ▪ The construction of this motor is similar to DC series motor in which the stator field windings are wound in series with armature windings. ▪ When the universal motor is fed with a DC supply, it works as a DC series motor. ➢ When current flows in the field winding, it produces an electromagnetic field. The same current also flows from the armature conductors. When a current carrying conductor is placed in an electromagnetic field, it experiences a mechanical force. Due to this mechanical force, or torque, the rotor starts to rotate. The direction of this force is given by Fleming's left hand rule. ▪ When fed with AC supply, it still produces unidirectional torque because, armature winding and field winding are connected in series, they are in same phase. ▪ Hence, as polarity of AC changes periodically, the direction of current in armature and field winding reverses at the same time. ▪ Direction of magnetic field and the direction of armature current reverses in such a way that the direction of force experienced by armature conductors remains same. 2 ▪ Regardless of AC or DC supply, this implies that an universal motor works on the same principle that a DC series motor works. Advantages: – High starting torque – Light weight – Compact – Runs at high speed Applications: – In hair dryers – In grinders – In table fans – Blowers – Vaccum cleaners Stepper Motor ▪ A stepper motor is a brushless DC motor whose rotor rotates in discrete angular increments, when its stator windings are energized in a programmed manner. ▪ The rotor of this motor doesn’t have any electrical winding, but has salient poles. ▪ The rotor rotates by the magnetic interaction between rotor poles and poles of sequentially energized stator windings. Types There are three types of stepper motor: – Permanent Magnet stepper motor – Variable reluctance stepper motor – Hybrid synchronous stepper motor 3 Stepper Motor Working: ▪ Unlike DC motors which rotates as soon as DC voltage is applied, stepper motors rotates according to the pattern of energizing the stator electromagnets. ▪ The electromagnets are energized by an external control circuit, for example, a microcontroller. ▪ To make the motor shaft turn, first one electromagnet is given power, which makes the gear’s teeth magnetically attracted to the electromagnet’s teeth. ▪ So when the next electromagnet is turned ON and the first is turned OFF, the gear rotates slightly to align with the next one and from there the process is repeated. ▪ Each of those slight rotations is called a step, with an integer number of steps making a full rotation Name: Description: ...
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