Unit 34 Single-Phase Motors
Split-Phase Motors
Unit 34
Single-Phase Motors
• Split-phase motor classifications:
– the resistance-start induction-run motor
– the capacitor-start induction-run motor
– the capacitor-start capacitor-run motor
• Split-phase motors use two separate
windings to create the necessary rotating
magnetic field. These windings are named
the start winding and the run winding.
Unit 34 Single-Phase Motors
Objectives:
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●
●
●
List the different types of split-phase motors.
Discuss the operation of split-phase motors.
Reverse the direction of rotation of a split-phase
motor.
Discuss the operation of a shaded-pole motor.
Unit 34 Single-Phase Motors
Objectives:
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●
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Unit 34 Single-Phase Motors
Resistance-Start Induction-Run Motor
• The start winding is more resistive than the
run winding which creates a phase shift
between the start and run windings.
• The start winding is removed when the
motor reaches 75% of its rated speed.
• The direction of rotation can be changed by
reversing the connection of either the start
winding or the run winding.
Unit 34 Single-Phase Motors
Resistance-Start Induction-Run Motor
Discuss the operation of a repulsion-type motor
Discuss the operation of a single-phase
synchronous motor.
Discuss the operation of a stepping motor.
Discuss the operation of universal motors.
The start winding has much smaller wire that the
run winding.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Resistance-Start Induction-Run Motor
Capacitor-Start Induction-Run Motor
The start winding is more resistive than the run
winding, creating a rotating magnetic field.
The start winding has much smaller wire that the
run winding.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Resistance-Start Induction-Run Motor
Capacitor-Start Induction-Run Motor
Running and starting currents are 35 to 40 out of
phase with each other.
An electrolytic capacitor is connected in series with
the start winding.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Capacitor-Start Induction-Run Motor
• A capacitor in series with the start winding creates a
90°phase shift between the start and run windings.
• The start winding and capacitor are removed when
the motor reaches 75% of its rated speed.
• The capacitor-start induction-run motor has more
starting torque that the resistance-start induction-run
motor, but the running characteristics are the same.
• The direction of rotation may be changed by
reversing the connection of either the start or the run
winding.
Capacitor-Start Induction-Run Motor
With the capacitor, the run and start-winding
currents are 90out of phase with each other.
Unit 34 Single-Phase Motors
Disconnecting the Start Winding
When
the
motor
reaches
approxi
mately
75% of
its rated
speed
the start
winding
will be
disconne
cted
from the
Unit 34 Single-Phase Motors
circuit.
The
following
methods
may be
used to
remove
the start
winding:
•
•
A •centrifugal switch may be used to disconnect the
start winding from the circuit.
Unit 34 Single-Phase Motors
•
A hot wire relay may be used to disconnect the
start winding from the circuit.
Unit 34 Single-Phase Motors
A current relay may be used to disconnect the start
winding from the circuit.
Unit 34 Single-Phase Motors
A solid-state
C
starting relay may be used to
disconnect
e
the start winding from the circuit.
n
t
r
i
f
u
g
Unit 34 Single-Phase Motors
a
l
Dual-Voltage Split-Phase Motors
s
w
i
t
c
h
H
o
t
Dual-voltage
windings for a split-phase motor.
w
i
r
e
•
r
e
l
a
y
C
u
r
r
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Dual-Voltage Split-Phase Motors
Dual-Voltage Split-Phase Motors
High-voltage connection for a split-phase motor
with two run and two start windings.
High-voltage connection with one start winding.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Dual-Voltage Split-Phase Motors
Dual-Voltage Split-Phase Motors
Low-voltage connection for a split-phase motor
with two run and two start windings.
Low voltage connection with one start winding.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Dual-Voltage Split-Phase Motors
Capacitor-Start Capacitor-Run Motor
Dual-voltage motor
with one start
winding labeled T5
and T8.
• The start winding and run capacitor remain in the
circuit after the motor has started.
• A second capacitor may be used to improve
starting torque that will be removed from the circuit
when the motor is near its rated speed.
• The run capacitor is typically an oil filled capacitor.
• Since the capacitor remains in the circuit the
power factor is close to unity.
Unit 34 Single-Phase Motors
Capacitor-Start Induction-Run Motor
Unit 34 Single-Phase Motors
Shaded-Pole Induction Motor
The start winding and run winding have the same
size wire.
• Shaded pole motors are fractional horsepower
motors used for low torque applications and generally
have a long life.
• A shaded-pole motor works on the principal of a
rotating magnetic field.
• The rotating magnetic filed is created by a shading
coil wound on one side of each pole piece.
• The direction of rotation is toward the shading coil.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Capacitor-Start Capacitor-Run Motor
Shaded-Pole Induction Motor
A capacitor-start capacitor-run motor.
Unit 34 Single-Phase Motors
Capacitor-Start Capacitor-Run Motor
A capacitor-start capacitor-run motor with an
additional starting capacitor.
A shaded pole motor has a shading coil which
creates the rotating magnetic field.
Unit 34 Single-Phase Motors
Shaded-Pole Induction Motor
The shading coil opposes a change of flux as
current increases.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Shaded-Pole Induction Motor
Repulsion-Type Motor
There is no opposition to magnetic flux when the
current is not changing.
• There are three basic repulsion-type motors:
• Repulsion Motor
• Repulsion-Start Induction-Run Motor
• Repulsion-Induction Motor
• Operates on the principal that like magnetic
poles repel each other.
• Highest starting torque of any single-phase
motor.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Shaded-Pole Induction Motor
Repulsion Motor
Brushes placed at a
90angle to the
poles does not
create any starting
torque.
The shading coil opposes a change of flux when
the current decreases.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Shaded-Pole Induction Motor
Repulsion Motor
Brushes placed
at a 0 angle to
the poles does
not create any
starting torque.
Four-pole shaded-pole motor..
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Repulsion Motor
Repulsion-Start Induction-Run Motor
Shifting the
brushes to a 15°
angle creates
maximum starting
torque.
Short-circuiting ring for brush-riding-type repulsionstart induction-run motor.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Repulsion Motor
Repulsion-Start Induction-Run Motor
Shifting the brushes
to the other side of
the pole piece will
change the
direction of rotation.
A radial commutator is used with the brush-liftingtype motor.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Repulsion-Start Induction-Run Motor
Repulsion-Start Induction-Run Motor
• A short circuiting ring short circuits the armature
windings at approximately 75% of the rated speed
causing the motor to run as an induction motor.
• There are two type of repulsion-start induction-run
motors:
• Brush lifting
• Brush riding
Brush-lifting-type repulsion-start induction-run
motor.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Repulsion Induction Motor
Single-Phase Synchronous Motor
Repulsion-induction motors contain both armature
and squirrel-cage winding.
A Holtz motor with a two pole stator will run at
1200 RPM.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Single-Phase Synchronous Motors
Stepping Motor
• Will operate at the synchronous speed.
• Use a shaded pole stator to create a rotating
magnetic field.
• Small and develop only fractional horsepower.
• Use the path of least reluctance to maintain the
synchronous speed.
• Two types of single phase synchronous motors are:
• Warren (General Electric motor)
• Holtz (Hysteresis)
• Rotor is a permanent magnet
• Convert DC electric impulses into mechanical
movement
• Output shaft moves through a specific angular
rotation each time the motor receives a pulse.
• The rotor can be held in its position by applying DC
power.
• Will operate as a two phase synchronous motor when
connected to two phase AC power
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Single-Phase Synchronous Motor
Stepper Motor
A Warren motor with a two pole stator will run at
3600 RPM.
The magnet aligns with the average magnetic pole.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Universal Motor
Universal Motor
●
●
●
●
Referred to as an AC series motor.
May be operated on AC or DC.
Creates high horsepower for it size and weight
because of its high operating speed.
Constructed similarly to a DC series motor by
having a wound armature and brushes.
Conductively compensated universal motor.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Universal Motor
Universal Motor
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●
●
A compensating winding is used to counteract the
inductive reactance of the armature winding.
Direction of rotation can be reversed by changing
the armature leads with respect to the field leads.
Used in many power tools and household
appliances.
Inductively compensated universal motor.
Unit 34 Single-Phase Motors
Unit 34 Single-Phase Motors
Universal Motor
Review:
1. There are three types of split phase motors:
–
–
–
Resistance-start induction-run
Capacitor-start induction-run
Capacitor-start capacitor-run
2. Split phase motors use a start and run
winding which are out of phase with each
other to create a rotating magnetic field.
Armature and brushes of a universal motor.
Unit 34 Single-Phase Motors
Review:
3. The direction of rotation of a split phase motor
is changed by reversing the connection of
either the start or the run winding.
4. The rotating magnetic field in a shaded-pole
motor is created by placing shading coils on
one side of the pole pieces.
Unit 34 Single-Phase Motors
Review:
5. There are three types of repulsion motors:
–
–
–
Repulsion
Repulsion-start induction-run
Repulsion-induction
5. There are two types of single-phase
synchronous motors
–
–
Warren
Holtz
Unit 34 Single-Phase Motors
Review:
7. Stepping motors generally operate on DC and
are used to produce angular movement in
steps.
8. Universal motors contain a wound armature
and brushes.
9. The direction of rotation of a universal motor
can be reversed by changing the armature
leads with respect to the field.