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