Dc Motors Test

What 3 things do a Brushless DC motor NOT contain?

A wound armature, commutator or brushes

used more than any other type of DC motor in industry

Compound Motor

opposite polarity voltage induced into armature as it spins through magnetic fields of pole pieces.

Counter-electromotive

Series aiding magnetic field windings

Cumulative Compound Motor

What is the principle of operation of a dc motor?

Dc motors opperate on the principle of attraction and repulsion of magnetism

The compound motor connection that should generally be avoided is the _____.

Differential

Permanent magnet motors have _____ efficiency than conventional field-wound motors.

Higher

Pushing or turning force

Torque

The pushing or turning force created by the magnetic field of the pole pieces and the magnetic field of the loop or armature is called

Torque

Very good speed characteristics

Shunt Motor

Referred to as constant speed motors

Shunt Motor

Dc series motors are generally used where

A constant torque was needed

The speed regulation of a DC motor is proportional to the _____.

Armature Resistance

In a compound DC motor control circuit, the field loss relay will disconnect the _____ if power is lost to the _____.

Armature, Shunt field

The motor that does not contain a wound armature, commutator, or brushes is the _____ motor.

Brushless Dc

does not contain a wound armature

Brushless Dc Motor

When a DC machine is used as a motor, the _______________ performs the function of a rotatory switch and maintains the correct direction of current flow through the armature windings.

Commutator

Uses both series and shunt field windings

Compound Motor

Series opposing magnetic field windings

Differential Compound

In general, what type of compound motor connection should be avoided?

Differential compound connection

A device that converts electrical energy into mechanical energy is called a(n)

Motor

Device used to convert electrical energy into mechanical energy

Motor

Does not need shunt fields or series field windings

Permanent Magnet Motor

pole pieces of motor need no excitation to become magnets

Permanent Magnet Motor

Dc compound motors are used to drive machines that require a

Relatively constant speed under varying loads

What is the most common way of changing the direction of rotation of a compound motor?

Reverse the connection of the armature leads

Speed is controlled by the amount of load connected to the armature

Series Motor

The best torque characteristics

Series Motor

What type of motor should never operate with no load?

Series Motor

The amount by which the speed decrease as load increases

Speed regulation

What 3 factors determine the amount of Cemf produced in the armature?

The speed of the armature The number of turns of wire in the armature The strength of the magnetic field of the pole pieces

What 2 factors determine the amount of torque developed by a DC motor?

The strength of the magnetic field in the pole pieces The strength of the magnetic field in the armature

When does a motor operate at base speed?

When full voltage is applied to both the armature and shunt field

How can a DC motor be made to operate above base speed?

When full voltage is applied to the armature and reduced voltage is applied to the shunt field

What limits the amount of current flow through the armature when power is first applied to the motor?

Wire resistance in the windings of the armature

Dc shunt motors should never be operated...

With the field circuit open

no natural speed limits and never operated with no load condition

Series Motor

Functions to disconnect power to the armature if shunt field current decreases below a certain level

Field-Loss Relay

Field windings are connected in parallel with armature windings and are the only set of windings

Shunt Motor

When a motor is connected differential compound, the _____ determines the direction of rotation of the motor at no load or light load.

Shunt field

Counter-electromotive force (CEMF) and back-EMF are names for the voltage induced into the armature of a DC motor.

True

A compound motor has _____ field windings.

Series and Shunt

Small permanent magnet motors that have lightweight rotors are often used as _____.

Servomotors

A series motor may be operated with no load connected.

False

The DC motor, known as a "constant speed motor," is the _____ motor.

Shunt

When the field winding of a DC motor is connected in parallel with the armature, the motor is called a _____ motor.

Shunt