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Unit 34Single-Phase Motors
Unit 34 Single-Phase Motors
Objectives:
● 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:
● 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.
Unit 34 Single-Phase Motors
Split-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
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
The start winding has much smaller wire that the run winding.
Resistance-Start Induction-Run Motor
Unit 34 Single-Phase Motors
The start winding is more resistive than the run winding, creating a rotating magnetic field.
Resistance-Start Induction-Run Motor
Unit 34 Single-Phase Motors
Running and starting currents are 35 to 40 out of phase with each other.
Resistance-Start Induction-Run Motor
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.
Unit 34 Single-Phase Motors
The start winding has much smaller wire that the run winding.
Capacitor-Start Induction-Run Motor
Unit 34 Single-Phase Motors
An electrolytic capacitor is connected in series with the start winding.
Capacitor-Start Induction-Run Motor
Unit 34 Single-Phase Motors
With the capacitor, the run and start-winding currents are 90out of phase with each other.
Capacitor-Start Induction-Run Motor
Unit 34 Single-Phase Motors
Disconnecting the Start Winding• When
the motor reaches approximately 75% of its rated speed the start winding will be disconnected from the circuit.
• The following methods may be used to remove the start winding:
• Centrifugal switch
• Hot wire relay
• Current relay
• Solid-state starting relay
Unit 34 Single-Phase Motors
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 starting relay may be used to disconnect the start winding from the circuit.
Unit 34 Single-Phase Motors
Dual-voltage windings for a split-phase motor.
Dual-Voltage Split-Phase Motors
Unit 34 Single-Phase Motors
High-voltage connection for a split-phase motor with two run and two start windings.
Dual-Voltage Split-Phase Motors
Unit 34 Single-Phase Motors
Low-voltage connection for a split-phase motor with two run and two start windings.
Dual-Voltage Split-Phase Motors
Unit 34 Single-Phase Motors
Dual-voltage motor with one start winding labeled T5 and T8.
Dual-Voltage Split-Phase Motors
Unit 34 Single-Phase Motors
High-voltage connection with one start winding.
Dual-Voltage Split-Phase Motors
Unit 34 Single-Phase Motors
Low voltage connection with one start winding.
Dual-Voltage Split-Phase Motors
Unit 34 Single-Phase Motors
Capacitor-Start Capacitor-Run Motor
• 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
The start winding and run winding have the same size wire.
Capacitor-Start Induction-Run Motor
Unit 34 Single-Phase Motors
A capacitor-start capacitor-run motor.
Capacitor-Start Capacitor-Run Motor
Unit 34 Single-Phase Motors
A capacitor-start capacitor-run motor with an additional starting capacitor.
Capacitor-Start Capacitor-Run Motor
Unit 34 Single-Phase Motors
Shaded-Pole Induction Motor
• 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
A shaded pole motor has a shading coil which creates the rotating magnetic field.
Shaded-Pole Induction Motor
Unit 34 Single-Phase Motors
The shading coil opposes a change of flux as current increases.
Shaded-Pole Induction Motor
Unit 34 Single-Phase Motors
There is no opposition to magnetic flux when the current is not changing.
Shaded-Pole Induction Motor
Unit 34 Single-Phase Motors
The shading coil opposes a change of flux when the current decreases.
Shaded-Pole Induction Motor
Unit 34 Single-Phase Motors
Four-pole shaded-pole motor..
Shaded-Pole Induction Motor
Unit 34 Single-Phase Motors
Repulsion-Type Motor
• 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
Brushes placed at a 90angle to the poles does not create any starting torque.
Repulsion Motor
Unit 34 Single-Phase Motors
Brushes placed at a 0 angle to the poles does not create any starting torque.
Repulsion Motor
Unit 34 Single-Phase Motors
Shifting the brushes to a 15° angle creates maximum starting torque.
Repulsion Motor
Unit 34 Single-Phase Motors
Shifting the brushes to the other side of the pole piece will change the direction of rotation.
Repulsion Motor
Unit 34 Single-Phase Motors
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
Unit 34 Single-Phase Motors
Short-circuiting ring for brush-riding-type repulsion-start induction-run motor.
Repulsion-Start Induction-Run Motor
Unit 34 Single-Phase Motors
A radial commutator is used with the brush-lifting-type motor.
Repulsion-Start Induction-Run Motor
Unit 34 Single-Phase Motors
Brush-lifting-type repulsion-start induction-run motor.
Repulsion-Start Induction-Run Motor
Unit 34 Single-Phase Motors
Repulsion-induction motors contain both armature and squirrel-cage winding.
Repulsion Induction Motor
Unit 34 Single-Phase MotorsSingle-Phase Synchronous Motors
• 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)
Unit 34 Single-Phase Motors
A Warren motor with a two pole stator will run at 3600 RPM.
Single-Phase Synchronous Motor
Unit 34 Single-Phase Motors
A Holtz motor with a two pole stator will run at 1200 RPM.
Single-Phase Synchronous Motor
Unit 34 Single-Phase Motors
Stepping Motor
• 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
The magnet aligns with the average magnetic pole.
Stepper Motor
Unit 34 Single-Phase Motors
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.
Unit 34 Single-Phase Motors
Universal Motor
● 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.
Unit 34 Single-Phase Motors
Armature and brushes of a universal motor.
Universal Motor
Unit 34 Single-Phase Motors
Conductively compensated universal motor.
Universal Motor
Unit 34 Single-Phase Motors
Inductively compensated universal motor.
Universal Motor
Unit 34 Single-Phase MotorsReview:
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.
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 MotorsReview:
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 MotorsReview:
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.
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