DC Motors

When a DC motor connected to 235 volts accelerates to a speed that generates a countervoltage of 115 volts, the total voltage in the motor is ? .

120v

DC shunt motors can develop about ? to ? of full-load torque upon starting.

250 to 300 percent

A motor connected to 280 volts has a resistance of 7 ohms. When the motor accelerates to full speed, the counter voltage is 245 volts; the total voltage in the motor is 35 volts and the current drawn is ? .

5A

When connected to 240 volts, a DC motor that has a winding resistance of 3.2 ohms at standstill draws ? .

75A

The interpoles are connected in series with the ? windings.

Armature

Torque is exerted on the ? when the plane of the armature loop is parallel to the field and the armature loop sides are at right angles to the magnetic field.

Armature

Interpoles reduce sparking at the ? of some DC motors.

Brushes

The function of a(n) ? is to keep armature windings in the correct polarity to interact with the main fields of a motor.

Commutator

DC ? motors are used mostly for special applications that require constant speed under load and high starting torque.

Compound

differential compound motor or undercompounded motor

DC motor where the current flows in opposite direction in series and shunt coils and the flux surrounding the two windings subtract.

permanent magnet motor

Dc motor that uses magnets not a coil of wire for the field windings

Shunt motor

Dc motor with the field windings in parallel with the armature

Which of the following is a common DC compound motor? A. DC cumulative-compounded motor B. DC collective-compound motor C. DC differential-compounded motor D. a. and b. E. a. and c.

E. A and C

DC permanent-magnet motors use magnets and coils of wire for the field windings. T/F

False

In a compound-wound generator, the series field is normally stronger than the shunt field. T/F

False

The fields in a DC motor often change in polarity. T/F

False

Compensating windings or Pole face windings

Field windings placed in slots of main poles

A DC ? operates on the principle that voltage is induced in a coil of wire when the coil is rotated in a magnetic field.

Genorator

Field Poles

Metal pieces mounted to the field frame that are used as field windings

The neutral plane is ? to the field flux when there is no current in the armature.

Perpendicular

A DC motor can be reversed by changing the ? of either the armature winding or the field winding.

Polarity

? voltage regulation occurs when the countervoltage at no load is greater than the terminal voltage at full load.

Positive

An external ? applies mechanical torque to the armature and series field circuit, which induces voltage and current in the generator.

Prime mover

The ? rule gives the direction of motion for current-carrying wire interacting with a stationary magnetic field.

Right hand motor

Negative voltage regulation occurs only with ? generators.

Series

? motors are used in moderate starting conditions and where constant or adjustable speed is required.

Shunt

A ? motor is a DC motor that has the field wiring connected in parallel with the armature.

Shunt

shunt wound generator

The field winding of a generator is connected in parallel with the generator armature

Connecting voltage directly to the field and armature windings of a DC motor allows the motor to produce higher torque in a smaller frame than with an AC motor. T/F

True

DC compound motors have shared characteristics of series motors and shunt motors. T/F

True

cumulative compound motor or overcompounded motor

a Dc motor where the current flows in the same direction in series and shunt coils and the flux surrounding the two windings adds together

series wound generator

a generator that has field windings in series with the amrature and the external circuit

compound wound generator

a generator that includes series and shunt field windings

generator

a machine that converts mechanical energy into electrical energy by means of electromagnetic induction

Direct current or DC motor

a machine that us Dc connected Field windings and armature to produce shaft rotation

direct current of DC Generator

a power source that supplies Dc when the armature is rotated

clogging

a variation in motor torque at very low speed caused by variation in the magnetic flux due to the alignment of the rotor and stator teeth in various rotor positions

Pigtail

an extended flexible connection or braided copper conductor

interpoles

are auxiliary poles placed between the main field poles and the motor

Compound motor

dc motor that has two sets of field windings with one in series and one in parallel with the armature

Commutator

is a ring made of insulated segments that keep the armature windings in the correct polarity to interact with the main field

stabilizing field winding

is a small series field winding placed over the top of the shunt field winding that improves stability of the fields while running with reduced current in the field circuit

brush rigging

is the entire assembly of brush, brush holder, insulator, and any windings in the correct polarity to that of the power source

the neutral plane

is the line through the armature cros section that is perpendicular to the maximum amount of magnetic flux

Field Windings

magnets or stationary windings used to produce the magnetic field in an alternator or motor

When the power is removed, DC ? motors provide some self-braking and produce relatively high torque at low speeds.

permanent magnet

A(n) ? connects a brush to either the positive or negative terminal of the DC source.

pigtail

With a(n) ? shunt field, the speed can be regulated by varying the field current, the armature current, or both.

self excited

The field windings in a ? -wound generator consist of a few turns of low-resistance wire because the large load current flows through them.

series

A DC ? -wound generator provides a source of positive and zero voltage regulation to the load.

shunt

separately sourced shunt field

shunt field connected to a different power supply then the armature

single sourced shunt field

shunt field connected to the same power supply as the armature

A ? winding is a small series field winding that improves stability of the fields while running with reduced current in the field circuit.

stabilizing field

series motor

the Dc motor with the field windings in series with the armature

Voltage regulation

the ability of a source to vary the output voltage in order to maintain system voltage as the load varies

Armature reaction

the distortion of the magnetic fields that happen when a current carrying wire is placed withing a fixed magnetic field

brush neutral

the position of the brushes where commutation can occur with the minimal induced voltage in the armature coils

Commutaion

the process where the armature current is periodically reversed in order to keep the motor torque in the same direction during the entire armature rotation

Armature

the rotating part of a DC motor, consisting of the laminated core with slots for the coils the main shaft and the commutator and brushes

Field Frame

the stationary part in the Dc motor or generator

torque ripple

variation in torque caused by variations in back emf or the current waveform