Chapter 12 and 13, Ch 14 + 16

Originally, most knife switches were made of __________, which required replacement after repeated arcing, heat generation, and mechanical fatigue.
A. silver
B. copper
C. aluminum
D. iron
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Terms in this set (118)
Originally, most knife switches were made of __________, which required replacement after repeated arcing, heat generation, and mechanical fatigue.
A. silver
B. copper
C. aluminum
D. iron
Copper
An ____________ was an improvement made to the original design of a knife switch.
A. eutectic alloy tube
B. transient suppression module
C. double-break contact
D. operating spring
Operating spring
A __________ is a device used only periodically to remove electrical circuits from their supple source.
A. disconnect
B. PLC
C. power pole
D. reset circuit breaker
Disconnect
Manual contractors are normally used _________.
A. to start and stop motors
B. with lighting circuits
C. as disconnects
D. in transformers
With Lighting circuits
The T-frame used with a 3phase manual contractor is activated by a _________ mechanism.
A. solenoid
B. knife switch
C. pushbutton
D. toggle switch
Pushbutton
An advantage of ___________ contacts is that the oxide (rust) that forms on the metal is an excellent conductor of electricity.
A. aluminum
B. steel
C. silver alloy
D. soft copper
Silver alloy
A _________ is the arrangement of contacts in such a a way that both sets of contacts cannot be closed at the same time.
A. overload relay
B. bimetallic thermodisc
C. dual-element interlock
D. mechanical interlock
Mechanical interlock
A ________ rotor is a condition when a motor is loaded so heavily that the motor shaft cannot turn.
A. locked
B. static
C. diffused
D. tied-down
Locked
A motor that is starting draws a tremendous __________ current (normally 6 to 8 times the running current) when the circuit is closed.
A. closing
B. contact
C. reset
D. inrush
Inrush
It is estimated that every ________ degree C rise over normal ambient temperature ratings for insulation can reduce the life expectancy of a motor by almost a year.
A. 1
B. 5
C. 10
D. 15
1
A _________ coil converts the excess current drawn by a motor into heat, which is used to determine whether the motor is in danger. A. eutectic B. overload C. heating D. meltingHeaterA ________ alloy is a metal that has a fixed temperature at which it changes directly from a solid to a liquid state. A. plasmic B. melting C. tripping D. eutecticEutecticAC manual starters are selected based on phasing, voltage, stater size, enclosure type, and _________. A. current B. wire size C. number of breaks D. number of polesNumber of poles.A _________ V, single phase power source has two hot wires, L1 and L2 (ungrounded conductors), and no neutral. A. 120 B. 230 C. 380 D. 575230___________ action is the principal operating mechanism for magnetic contactors. A. Torque B. Variable C. Electromechanical relay D. SolenoidSolenoidTwo-wire control is normally used for __________ installations where an immediate return to service after a power failure is required. A. emergency B. dense urban C. remote or inaccessible D. general-purposeremote or inaccessible_________ control provides low-voltage release and low-voltage protection. A. Two-wire B. Three-wire C. AC D. DCThree-wireAC contactor assemblies are made of laminated ____________, while DC assemblies are solid. A. steel B. iron C. silver alloy D. aluminumSteel_________ are used to reduce the distance required and yet quench arcs quickly. A. Arc chutes B. Arc traps C. Magnetic blowout coils D. Bimetallic stripsMagnetic blowout coils_________ overload relays are extremely quick to reset because they do not require a cooling-off period before being reset. A. Bimetallic B. Melting alloy C. Magnetic D. Current transformerMagneticA __________ overload relay is an overload relay that resets automatically. A. magnetic B. bimetallic C. ambient temperature D. inherentbimetallicThe ________ indicator on a trip indicator informs the operator or electrician why the unit is not operating and that it is potentially capable of restarting with an automatic reset. A. green B. yellow C. orange D. redRedA ___________ is used to change the amount of current flowing to a motor but reduces the current to a lower value for the overload relay. A. thermistor B. circuit breaker C. current transformer D. photoelectric relayCurrent transformerIf a motor has an FLC rating of 10 A with an SZF of 1.15, the excess short-term current equals _______ A. A. 8.7 B. 8.85 C. 11.15 D. 11.511.5Overload relay devices are normally rated to trip at a specific current when surrounded by ambient temperature of _________ degrees C. A. 30 B. 40 C. 50 D. 6040For fully reliable motor protection, heat coils should be selected based on the motor ____________ rating shown on the motor nameplate. A. full-load current B. service factor C. ambient temperature D. horsepowerFull-load currentAn __________ motor protector is an overload device located directly on or in a motor to provide overload protection. A. internal B. fixed C. inherent D. auxiliaryInherentA ________ is an overcurrent protection device with a mechanism that automatically opens the circuit when an overload condition or short circuit occurs. A. thermistor B. circuit breaker C. bimetallic thermodisc D. current transformerCircuit breakerContactor and magnetic motor starter modification devices include additional electrical contacts, power poles, pneumatic timers, transient suppression modules, and ________. A. photoelectric switches B. internal DMMs C. additional busbar connections D. control circuit fuse holdersControl circuit fuse holdersAdditional NC contacts are used to turn on additional loads anytime a contactor or starter is OFF, as well as to provide electrical _________. A. arc suppression B. solenoid action C. interlocking D. trip indicatorsInterlockingNormally, only one ________ unit with one or two contacts is added per contactor or motor starter. A. pneumatic timer B. power pole C. additional electrical contact D. transient suppression modulePower poleTransient suppression modules normally consist of resistance/capacitance (RC) circuits and are designed to suppress the voltage transients to approximately ________% of peak coil supply voltage. A. 100 B. 200 C. 300 D. 400200Loose connections in the power circuit of contactors and motor starters cause __________. A. transient voltages B. arcing C. overheating D. ghost voltagesoverheatingWhen troubleshooting a contactor or motor starter, the voltage is acceptable if the voltage reading is within ______% of the motor voltage rating. A. 10 B. 20 C. 30 D. 4010________ state a problem, its possible cause(s), and corrective action(s) that may be taken. A. Nameplates B. Manufacturer motor charts C. Motor starter wiring diagrams D. Troubleshooting guidesTroubleshooting guidesMotors operate on the principle that when a _____-carrying conductor is placed in a magnetic field, a force that tends to move the conductor out of the field is exerted on the conductor. A. voltage B. power C. current D. resistanceCurrentThe electron flow motor rule states that the _______ points in the direction of the electron current flow in the conductor. A. index finger B. middle finger C. ring finger D. thumbmiddle fingerThe intensity of the magnetic field and the amount of current in a conductor are normally changed to increase the _______ on the conductor. A. force B. horsepower C. work D. torqueforceA DC motor consists of _____ windings, an armature, a commutator, and brushes. A. field B. variable C. shunt D. capacitorFieldA commutator connects each armature winding to the brushes using _____ bars (segments) that are insulated from each other with pieces of mica. A. iron B. silver C. aluminum D. copperCopperA spring placed behind the brush, forces the brush to make contact with the ______. A. armature B. commutator C. pigtail D. motor enclosureCommutatorA commutator rotates in ______ degree increments. A. 90 B. 120 C. 180 D. 360180DC motors require more maintenance than AC motors because they have _______ that wear. A. armatures B. brushes C. commutators D. pigtailsBrushes_______ is exerted on an armature when it is positioned so that the plane of the armature loop is parallel to the field, and the armature loop sides are at right angles to the magnetic field. A. Torque B. Inertia C. Voltage D. CurrentTorqueA DC series motor is a DC motor that has the series field connection in series with the _______. A. brushes B. commutator C. armature D. main poleArmatureThe ______ that is produced by a motor depends on the strength of the magnetic field in the motor. A. voltage B. horsepower C. work D. torqueTorqueA DC _____ motor should always be connected directly to the load and not through belts, chains, etc. A. stepper B. series C. permanent-magnet D. shuntSeriesIn a DC shunt motor, if the _______ to the armature is reduced, the speed is also reduced. A. current B. power C. voltage D. torqueVoltageA _____ is used to increase or decrease the strength of the field or armature in a DC shunt motor. A. rheostat B. encoder C. CEMF D. stepperRheostatThe wires extending form the shunt field of a DC shunt motor are marked _____. A. A1 and A2 B. F1 and F2 C. P1 and P2 D. S1 and S2F1 and F2Stepper motors are used in applications that require precise control of the position of the ______. A. brushes B. motor shaft C. field winding D. commutatorMotor shaftIn a stepper motor, the permanent magnet is called the _____ or armature. A. stator B. encoder C. rotor D. shuntRotorBecause the stator coils are turned on and off rapidly to control a stepper motor, ____ switches are used. A. variable B. dual-field C. mechanical D. sold-state transistorsolid-state transistorTo help reduce damage to switch contacts, a _____ circuit is used to protect the switch. A. snubber B. PLC C. SRC D. triacSnubberAn _____ is a sensor (transducer) that produces discrete electrical pulses during each increment of shaft rotation. A. open-loop device B. optical relay C. encoder D. pulse sensorEncoderThe direction of shaft rotation is controlled by the polarity of the produced magnetic field in the ______. A. commutator B. armature C. rotor D. stator coilStator coil______ is produced when a force overcomes a resistance. A. Torque B. Horsepower C. Half-wave power D. WorkWork______ is the force that produces rotation. A. Resistance B. Torque C. Work D. HorsepowerTorqueHorsepower (HP) is a unit of power equal to ____ lb-ft per min. A. 1 B. 550 C. 746 D. 33,00033,000The _____ is the base unit of electrical power. A. ampere B. ohm C. watt D. voltWattThe _______ of a motor determines the size of a load that the motor can operate and the speed at which the loads turns. A. horsepower B. voltage C. force D. torqueHorsepowerThe requirements a motor must meet in controlling a load include work, force, torque, and horsepower in relation to _____. A. current B. voltage C. size D. speedSpeedMost motors are designed so that the brushes and the ____can be inspected without disassembling the motor. A. armature B. commutator C. windings D. shaftCommutatorA ______ circuit is a circuit in which current takes a shortcut around the normal path of current flow. A. short B. grounded C. open D. closedShortA _______ should be used for more accurate testing of insulation. A. ammeter B. oscilloscope C. DMM D. megohmmeterMegohmmeterTerminal markings S1 and S2 always indicate the ______ field leads. A. armature B. commutator C. series D. shuntSeriesFull-wave rectified power is obtained by placing a _____ in an AC power line. A. amplifier B. capacitor C. triac D. bridge rectifierBridge rectifier______ wear faster than any other component of a DC motor. A. Magnets B. Brushes C. Commutators D. Insulated componentsBrushesDashpot, synchronous clock, and sold-state timers are ___ timers.stand-alone___ timers are the most common stand-alone timer used in control applications today.Solid-stateA ___ timer is a timer that provides time delay by controlling how rapidly air or liquid is allowed to pass into or out of a container through an orifice (opening) that is either fixed or variable in diameter.dashpotSolid-state timers are less susceptible to outside environmental conditions because they, like relay coils, are often encapsulated in ___ for protection.epoxy resinThe ___ section of a PLR is where the circuit's digital (ON/OFF, OPEN/CLOSED, etc.) switches are connected.input___ timers are the oldest type of industrial timers.Dashpot___ timers are normally discarded when they fail since they cost less than other timers.Solid-stateA(n) ___ timer can be designed to open or close a circuit after a preset time delay.on-delayA(n) ___ timer may also be used for plugging a motor to stop during emergency stops.off-delayA(n) ___ timer is a device in which the contacts change position immediately and remain changed for the set period of time after the timer has received power.one-shotA(n) ___ recycle timer is a timer that has independent adjustments for the on and off time periods.asymmetrical___ timers are the most common type of timer in use.On-delayIn a(n) ___ diagram, the top line shows the position of the control switch and the bottom line shows the condition of the load.operationalA(n) ___ timer is a device in which the contacts cycle open and closed repeatedly once the timer has received power.recycle___ diagrams are required on multiple-contact timers because several different connection points must be located and wired to the timer for it to perform properly.WiringA(n) "___" indicated when the load is de-energized.OA ___-controlled timer is a timer that requires the control switch to be connected so that it controls power to the timer coil.supply voltageThe advantage of the ___ control method is that the control switch can be wired using low-voltage wire (AWG 16, 18, or 20).contactA(n) ___-controlled timer is a timer controlled by an external sensor in which the timer supplies, the power required to operate the sensor.sensor___ could be added to a circuit if the circuit requires a momentary input, such as a pushbutton, it initiate timing.MemoryThe most common problem of contact-based timing circuits is ___ failure.contactA ___ timer is an integrated circuit (IC) that can function as either a timer or an oscillator.555A variable resistor and a(n) ___ are used to determine the amount of time delay in a 555 timer.capacitorA preset value of 1234 with a time base setting of 0.01 sec is equal to ___ sec.12.34A(n) ___ timer is a timer that does not maintain its current accumulated time value when its control input signal is interrupted or power to the timer is removed.nonretentiveModern industrial control circuits are often connected to DC electronic circuits that include a(n) ___ as their output.transistorA ___ is the electronic equivalent of a toggle switch.flip-flopA ___ clock allows for outputs to be turned on and off at preset times of the day and days of the week.real-timeA ___ is a counting device that keeps track of the total number of units or events and displays the total counted value.totalizerA(n) ___ counter is a device used to count inputs and provide an output (contacts) after the preset count value is reached.upA(n) ___ counter is a device used to count input from two different inputs, one input that adds a count and another input that subtracts a count.up/downA(n) ___ can be used when only the total number of units or events is required to be known.totalizerThe ___ is the stationary part of an AC motor.stator___ the stator pole is the simplest method used to start a 1 phase motor.ShadingWhen starting a split-phase motor, both the running windings and the starting windings are ___.connected in parallelWhen a split-phase motor reaches approximately ___% of full speed, the centrifugal switch opens, disconnecting the starting winding from the circuit.75When a motor is first connected to power, the ___ of the starting winding is lower and the resistance is higher than the running winding.reactanceA ___ motor has the starting winding and capacitor connected in series at all times.capacitor-runThe capacitor used in the starting winding gives a ___ motor high starting torque.capacitor-startTo develop a rotating magnetic field in a 3 phase motor, the ___ must be connected to the proper voltage level.stator windingsIn a 3 phase motor, the leads that are brought out externally are labeled with a(n) ___.TThe ___ of a motor should be grounded, especially if the motor is used in a damp location.frameThe maximum recommended acceleration time depends on the motor ___ size.frameAn electrician can observe the even blackening of all motor windings that occurs when a motor has failed due to ___.overloadingA motor with a service factor of 1.0 is derated when it operates at altitudes above ___'.3300Some ___ motors include a thermal switch that automatically turns the motor off when it overheats.split-phaseAll capacitors are made with two conducting surfaces separated by ___.dielectric materialA dual-voltage, wye connected motor has ___ separate circuits.fourA(n) ___ may be used to determine the winding circuits on an unmarked motor by conncting one test lead to any motor lead and temporarily connecting the other test lead to each remaining motor lead.continuity tester___ motors that fail are usually replaced.Shaded-pole