TPC 206 DC Equipment Flashcards
Which of the following cells has the shortest service life?
Lead Acid
In the electroplating plating process, the object to be plated is made the…
Cathode
Which device converts alternating current to direct current?
Rectifier
A typical motor-generator set for a charging storge batteries uses a ______ on the equipment to shut off the charger after the correct amount of charging time.
timer unit
Electroplating a piece of metal requires a _____ potential difference between the anode and the cathode an a _______ current.
Low; High
A solenoid used for closing a valve or releasing a brake is usually made with a _____ shaped magnet.
C-T
The movable magnetic arm of a relay is called the…
Armature
A major cause of a noisy solenoid is loose
Laminations
Incorrect seating of its plunger can cause a solenoid to
draw too much current
To increase the service life of DC relay contacts that carry large inductive loads, a _____ can be connected in parallel with the load.
Diode
Which part of a generator makes electrical contact between the brushes and the coils of wire in the armature?
Commutator
In DC generation, the number of pulses during each rotation of the armature ______ with an increase in the number of ______.
increase; field poles
A DC generator that supplies a nearly constant potential difference between terminals is called a _____ generator.
Compound
Eddy currents in a DC generator cause _______ losses.
Magnetic
The main parts of a DC generator are the field poles, brushes and brush rigging, commutator, frame, and…
Armature
The field windings in a DC compound motor are connected so that _____ with the armature.
one is in parallel, and one is in series
The only kind of DC motor to run faster under high load than under low load is a _____ motor.
Differential compound
Another name for potential difference is
electromotive force
One horsepower is equal to 550ft-lb per second or
745.7 joules per second
Shunt, series, and compound refer to different kinds of
DC motors
A winding that doubles back on itself in a drum armature is called a ______ winding.
Lap
Which type of power loss varies with the speed of a DC armature and the volume or iron in the core?
Hysteresis loss
Each DC armature coil is wound on a form, then insulated, _______ and baked.
varnished
The two types of windings used on drum armatures are lap windings and ________ windings.
wave
Preventative maintenance of an armature involves periodic inspections and tests to determine its condition, as well as _______ to preserve the insulation
Periodic cleaning
A time-delay feature can be added to a magnetic overload relay in the form of an
oil dashpot
The current at which a series lock out relay will close can be changed by adjusting the
size of the air gap
A disk brake is designed to be mounted on the ______ of a motor
end bell
Overload relays are usually of the ______ or _______ type.
Thermal; magnetic
Whenever lockout relays are used in DC circuits, the controller is called a ______ starter.
Current-limiting
An adjustable-voltage motor controller varies the potential difference applied to the motors
armature
Controllers are rated by duty as _____ or ________.
Continuous; intermittent
A NC overload relay contact in a magnetic motor controller is opened by means of a mechanism tripped by an overcurrent. In a manual motor
Mechanically
Overload relays and contactors are not designed to protect a motor from extremely high ______ ; fuses and circuit breakers offer this kind of protection
current
If a motor is to be started and stopped from several stations, all of the START pushbuttons are connected in ________ and the STOP push buttons in ______.
Parallel; series
The emissions of electrons by heating is called _______ emission.
Thermionic
Semiconductor failures caused by high temperatures usually occur
in a fractions of a second
Which of the following lowers the peaks and raises the valleys in a rectifiers output?
Capacitor
Four diodes in a diamond shaped circuit can deliver full-wave rectification in a _______ rectifier circuit.
Bridge
Most automobiles use a _________ generator called an alternator, along with rectifiers, to charge and run the car’s battery and electrical system
three-phase AC
The part of an SCR that either allows or prevents the flow of electricity is called the
Gate
An SCR in an AC circuit can be turned on earlier in the half-cycle in order to _______ the ______.
increase; power to the load
Increasing the effective current and power level from an SCR controller to a DC motor requires
narrower intervals between pulses
What turns on SCR on and off?
trigger pulses
One very effective method of controlling an SCR in an AC circuit is called _______ control.
phase
A sudden drop in the potential difference between terminals usually indicated an _________ circuit in the field winding of a DC _________.
open; generator
Before installing a new field coil in a machine, you should
determine the polarity of the new coil
If silver relay contacts become roughened or pitted, you should
do nothing
Inspect the commutator risers on a dc armature regularly to determine the condition of the solder that secures the windings to the
segments
Unless the manufacturer’s instruction book tells you otherwise, brush pressure should be _______ psi per brush contact area.
1 1/2- 2 1/2
