Week 2a

What is the purpose of the commutator?

To make the armature develop torque continually in the same direction

Which of the following factors is torque dependent on?

The position of the coil in the field

What is the "neutral plane

The plane defined by the positions where the windings are moving parallel to the field

Which rule is used to determine motor rotation?

The right hand rule

What is the force that makes the armature turn?

Torque

What is the purpose of the commutator?#1

To transfer electricity from the brush assembly into the armature windings

What changes the main field in a motor?

- Interpoles

Pole shoe

How is the direction of rotation changed in a motor with an electromagnetic field?

By reversing the voltage applied to the field

Field windings

Armature

What is used to control how far a motor can drive it's load?

Proximity switches

How is the direction of rotation changed in a motor with an electromagnetic field?#2

By reversing the voltage applied to the armature

What is used to control how far a motor can drive it's load?#2

Limit switches

What determines the amount of armature reaction in a motor? -

The amount of current in the armature

If armature reaction is not corrected for what is the end result?

- Power loss due to arcing and heating of the brushes

How is speed controlled in a motor with an electromagnetic field? -

By changing the applied voltage/current to the field

What is the "neutral plane"?

The plane defined by the positions where there is no current being induced in the windings

What changes the main field in a motor?#2

Compensating windings

What part is sometimes "built in" to a motor to protect it form overheating?

A thermal switch

Which of the following factors is torque dependent on?#2

The strength of the magnetic field

How can torque ripple be reduced?

Add arms to the armature

Cooling fan

How is speed controlled in a permanent magnet motor?

By changing the applied voltage/current

Which of the following factors is torque dependent on?#4

The number of turns in the coil

Why does the direction of rotation NOT change in a motor with an electromagnetic field then the main power leads are reversed?

- Because the armature and field current directions are changed at the same time, leaving the torque in the same direction

End frame

What is used to change the current into a motor on older aircraft?

- A resistor

Brush

What is it called when the toque produced is not constant?

Torque ripple

In which direction will a wire in a magnetic field move?

Towards the weaker field

How is the direction of rotation changed in a motor with an electromagnetic field?#5

By reversing the voltage applied to the armature OR the field

How do you increase the speed in a motor with an electromagnetic field?

By decreasing the field current

If the voltage to a permanent magnet motor is increased what will happen?

- The speed will increase

How is the direction of rotation of a permanent magnet motor changed?

By reversing the voltage applied to the motor

What is the effect of armature reaction in a motor?

The shifting of the neutral plane in the direction of rotation

What changes the main field in a motor?#5

The secondary magnetic field created by the current in the armature windings

The motion in an electric motor is due to what?

- The interaction between the field and armature magnetic fields

Brush assembly

How do you decrease the speed in a motor with an electromagnetic field?

By increasing the field current

What is the purpose of an electric motor?

To create rotational motion

What is the purpose of the commutator?#77

To convert DC into AC