Chapter 20 AC/DC
Diode
A flywheel _________ is used in an alternator to suppress the inductive voltage that occurs when the exciter switch is opened.
F
A neutral line is required for a properly balanced 3 load
F
A power quality meter is used to analyze circuits by measuring the true power in a 3 system.
increase current levels
A power-correcting capacitor does all of the following except _________.
T
A rotor is the rotating part of an AC motor
T
A wye connection is sometimes referred to as a star connection.
T
A wye-connected generator has line voltages that are equal value.
Coil
A(n) ________ is the number of completely isolated circuits that a relay can switch.
kVa
AC generators are rated in _________
Tangent
Alternator is another name for an AC________.
T
An AC generator cannot produce output voltage before the rotor has been excited
Reactive
An _________ circuit is either capacitive or inductive and has a power factor of less than 1
Wye
An _________ connection is a connection that has one end of each coil connected together and the other end of each coil left open for external connections
Rectifier
An _________ is a device that converts AC voltage to DC voltage by allowing the AC voltage and current to flow in only one direction.
Armature
An _________ is a movable coil of wire in a generator that rotates relative to the magnetic field.
Stator
An _________ is a part of a generator that remains in a stationary position.
Brush
An _________ is the sliding contact that rides against the slip rings and is used to connect the armature to the external circuit.
Swamping
An _________ resistor is a resistor that is used to suppress the high inductive kick of an exciter current.
T
Appliances that produce heat or provide incandescent light are examples of resistive loads.
1.15
For 3 and 1 power systems to deliver the same amount of power to their respective loads, a 1 power system requires about _________ times the copper required for a 3 power system.
T
Loads can be both inductive and resistive.
F
Single-phase power creates smoother DC output with less filtering than three-phase power
T
The line currents of a delta-connected generator have equal values and are located 120 degrees apart.
F
Three-phase motors require more components to operate and often require more maintenance than 1 motors
T
Three-phase power is often preferred to single-phase power because less copper is used to deliver a given amount of power.
Conductors
Three-phase power systems use three individual _________ to transmit power.
Generators
_________ are used to produce three-phase power.
Excitation
_________ current is the DC used to produce electromagnetism in the fields of a DC motor or generator or in the rotor of an AC generator
Plugging
_________ is a method of motor braking in which the motor connections are reversed so that the motor develops a countertorque that acts as a braking force.
Jogging
_________ is the frequent starting and stopping of a motor for short periods.
Generated
_________ voltage is a voltage produced in a closed path or circuit by the relative motion of the circuit or its parts with respect to magnetic lines of force.
six
A 3 generator has _________ leads coming from the armature windings.
Delta
A _________ connection that has each coil connected end to end to form a closed loop.
Power quality meter
A _________ test instrument that measures, displays, and records voltage, current, and power, as well as power problems such as sags, swells, transients, and harmonics.
Capacitors
A common method for correcting the power factor of a circuit is to connect _________ across the load.
F
Clamp on ammeters measure current by measuring the strength of the voltage around a single conductor.
T
Each branch of a delta connection has the same value of impedance.
F
General voltage is a voltage produced around a closed path or circuit by a change in the magnetic lines of force linking the path.
F
Generated voltages in a delta-connected generator have equal values from the load voltages.
120
In a three phase power system, the voltage of each conductor is _________ out of phase with that of the other conductors.
F
In a wye connection, five leads are connected together, while the other five leads are brought out for connecting to the load.
F
The higher the power factor, the higher the operating cost.
90
Maximum induced voltage occurs when the conductor cuts the field at _________ degrees
Pile
Metallic rings that are connected to the ends of the armature and are used tp connect the induced voltage to the brushes are known as __________ rings.
Factor
Power ________ is the ratio of true power used in an AC circuit to apparent power delivered to the circuit.
90
Power factor correction is the process of correcting power factor to at least _________ %
in phase
Power factor is _________ for a resistive load
before the electric motor drive
Power-correcting capacitors must be placed _________
Pitch
The _________ of a coil is how tightly the windings of a coil are wound.
T
The greater the number of poles, the greater the frequency of the generated voltage
1.73
When magnitudes are equal and 120 degrees apart, the resultant vector can be obtained by multiplying one vector by _________
45
When resistance equals inductive reactance in each phase, current lags source voltage by _________ degrees
Motor under full load
Which of the following is not an example of an inductive load?
F
in a capacitive reactive circuit, voltage leads the current.