Motors 2 Lesson 1
Determine the resistance and tolerance of a power resistor with color bands of brown, red, orange, and gold.
12000 5%
When maximum resistance is applied to the rotor circuit of a wound-rotor motor, the starting torque is about ? of the motor's full-load torque (FLT). Select one: a.30% b.125% c.200% d.1000%
200% pg 122
Cartridge fuses are available with amperage ratings from 0 amperes to ? . Select one: a.10 A b.75 A c.6,000 A d.100,000 A
6,000A
The ? connection of a dual-voltage motor is used for low voltage while the ? connection is used for high voltage. Select one: a.parallel / series b.primary / secondary c.secondary / primary d.series / parallel
A. Parallel / Series
A ? provides a connection to a stationary circuit by riding against a rotating component. Select one: a.brush b.drum switch c.pigtail d.3-pole rheostat
Brush
? should be replaced if they are worn down to a fraction of their length because they lose contact with the slip rings. Select one: a.Brushes b.Insulators c.Pigtails d.Resistors
Brushes
Match the procedure for troubleshooting fuses to the corresponding letter in the illustration. (Note: "G" represents a bad fuse.)
C F D B G E A Note: The text does not cover sizing of OCPD, conductors, and feeders. These topics are covered in Code lessons. However, refer to Chapter 11 of the Electrical Systems textbook, which is based on the 2008 Code and NEC Article 430. The correct answer is: Check the enclosure and interior parts for deformation, displacement of parts, and burning. → C, Check the fuses. → F, Check the voltage between each pair of power leads. → D, Open the door of the safety switch or combination starter. → B, Replace any bad fuses. → G, Test the enclosure for grounding if voltage is present and at the correct level. → E, Turn the handle of the safety switch or combination starter to the OFF position. → A
A capacitor start-and-run motor has the same starting torque as a ? motor. Select one: a.capacitor-run b.capacitor start c.shaded-pole d.split-run
Capacitor start
ID the type of motor
Capacitor start and run
A permanent split-capacitor motor is also known as a ? motor. Select one: a.capacitor-run b.capacitor start-and-run c.shaded-pole d.split-run
Capacitor-run
A ? switch removes the capacitor and start winding from the circuit after the motor accelerates in a capacitor-start motor. Select one: a.centrifugal b.drum c.foot d.rheostat
Centrifigul
Which of the following is a method for terminating inside a 1-ph motor terminal box? I. Direct wire method II. Terminal post method III. Terminal post with links method Select one: a.I. and II. b.I. and III. c.I., II., and III. d.II. only e.III. only Feedback
Direct wire method Terminal post method terminal post with links method
The large thermal mass of ? resistors absorb the heat generated during starting, but these resistors are rarely used anymore because other types are available that can also dissipate heat. Select one: a.electrolytic b.external c.primary d.secondary
Electrolyic pg 121 Electrolyic resistors contain a conductiove electrolyte solution. These resistors have a large thermal mass to absorb the heat generated during starting, but are seldom used anymore because other types of resistors are available that can dissipate the heat.
Match Endbell Capacitor Rotor Bearing Shaft Fan Stator
Endbell Capacitor Rotor Bearing Shaft Fan Stator
CBs offer the benefit of not damaging themselves but are not resettable after an overload has cleared. Select one: True False
FALSE
Wiring methods inside a terminal box include terminal post, direct wire, and direct wire with links. Select one: True False
FALSE (it is false even though the next question says that all three methods terminate in the box, this question may be fixed in the future)
In thermal-magnetic CBs, the thermal element provides faster protection for ground faults and short circuits while the magnetic element is used for overload protection. Select one: True False
False
To avoid nuisance tripping due to equipment startup characteristics, time-delay fuses do not allow overcurrents to exist. Select one: True False
False
An OCPD must be used to provide protection from short circuits and ? . Select one: a.circuit breakers b.fuses c.ground faults d.overloads
Ground Faults
A(n) ? circuit breaker operates immediately and has no delay between the sensing element and the tripping action of the device. Select one: a.adjustable-trip b.instantaneous-trip c.inverse-time d.non-adjustable-trip
Instantaneous- Trip
Unlike a standard squirrel-cage induction motor, the rotor of the wound-rotor motor is constructed by placing ? in the slots. Select one: a.insulated coils of wire b.iron bars c.power resistors d.squirrel-cage bars
Insulated coil wire pg 119 constructed placing insulated coils of wire in the slots instead of the solid conductor bars used in the squirrel cage induction motor.
The ? rating of an OCPD is the maximum amount of current that can be safely applied while still maintaining the physical integrity. Select one: a.current b.interrupting c.thermal d.voltage
Interrupting
A wound-rotor ? is designed to provide rotor circuit resistance during startup and remove that resistance when the motor is up to speed. Select one: a.motor starter b.regulator c.secondary resistor d.winding controller
Motor Starter Pg 124
A(n) ? in a motor is caused by a load that exceeds the full-load rating of the motor. Select one: a.ground fault b.overload c.phase imbalance d.short circuit
Overload
A(n) ? indicates the maximum length of time it takes for the overload relay to trip at 600% overload. Select one: a.current rating b.instantaneous-trip circuit breaker c.inverse-time circuit breaker d.overload class rating
Overload class rating
A 3-pole rheostat is used to switch a set of ? in or out of a wound-rotor circuit. Select one: a.capacitors b.fuses c.inductors d.resistors
PG 125 Resistors Note: The Motors textbook treats the 3-pole rheostat as a switch with tapped resistors, but commonly the 3-pole rheostat is a variable resistor and not an actual switch selecting various tapped resistors.
The windings of a 3-phase wound-rotor motor are located ? electrical degrees apart in the slots in the stator. a.60 b.90 c.120 d.180
Pg 119 The windings are placed in slots 120 electrical degrees apart
Drum switches, 3-pole rheostats, and silicon-controlled rectifiers (SCRs) are common types of ? for wound-rotor motors. Select one: a.commutation controller b.regulators c.starters d.timers
Regulators pg 125
The speed of a wound-rotor motor may be reduced by increasing the ? of the rotor circuit while the motor is running, in order to reduce the current in the rotor windings. Select one: a.frequency b.inductance c.magnetism d.resistance
Resistance resistors that were connected to the rotor can be used to reduce the speed of the motor, increasing the the resistance of the rotor while it is running reduces the current in the rotor windings and reduces the speed of the motor pg 124
A brush rigging does not contain ? in its assembly. a.a brush holder b.insulators c.resistors d.wiring
Resistors
A(n) ? condition causes the current to rise hundreds of times higher than normal at a very fast rate. Select one: a.overload b.short-circuit c.single phasing d.voltage sag
Short-circuit
A ? is a solid-state device used to switch a set of resistors in or out of a wound-rotor motor circuit that requires continuous speed variations. Select one: a.drum switch b.silicon-controlled rectifier (SCR) c.3-pole rheostat d.none of the above
Silicon-controlled rectifier
Brushes and ? are used to connect the rotor of a wound-rotor motor to an external set of secondary resistors. Select one: a.drum switches b.pigtails c.rectifiers d.slip rings
Slip Rings
ID the type of motor
Split Phase
A wound-rotor motor delivers higher ? than a squirrel-cage motor without creating an overload of the electrical system. Select one: a.current draw b.inductance c.resistance d.starting torque
Starting Torque
A ? overload relay uses a resistive heating element to open a set of contacts. Select one: a.digital b.magnetic c.pneumatic d.thermal
Thermal
A(n) ? circuit breaker uses a bimetal strip connected in series with the load to open a circuit. Select one: a.instantaneous trip b.magnetic c.switch d.thermal-magnetic
Thermal-magnetic
? fuses are also known as dual-element fuses. Select one: a.Current limiting b.Non-current limiting c.One-time d.Time-delay
Time- Delay
A ground fault is an unintentional connection between an ungrounded conductor and any grounded raceway, box, enclosure, or fitting. Select one: True False
True
A heater coil converts the excess current drawn by a motor into heat. When enough heat has been generated, it melts the eutectic alloy. The eutectic alloy is used in conjunction with a mechanical mechanism to activate a tripping device when an overload occurs. Select one: True False
True
A multispeed capacitor-run motor changes speed by adding impedance to the run winding and increasing the slip, not by changing the number of poles. Select one: True False
True
Both magnetic and thermal-magnetic circuit breakers use a spring-loaded electrical contact that opens the circuit. Select one: True False
True
Both single-phase and 3-phase motors have a stator and rotor. Select one: True False
True
Fuses and circuit breakers (CBs) are used for ground-fault and short-circuit protection; overload relays are typically used for overload protection. Select one: True False
True
Fuses themselves do not need to be maintained. The fuse holders, terminations, and disconnects should be inspected regularly. Select one: True False
True
The NEC® requires overcurrent protection of motor installations. Select one: True False
True
The melting point of a eutectic alloy never changes and is not affected by repeated melting and resetting. Select one: True False
True
The purpose in making motors for two voltages is to enable the same motor to be used with two different power-line voltages. Select one: True False
True
Under any load condition, the motor draws only the amount of current required to keep the shaft rotating at the rated revolutions per minute. Select one: True False
True
To cause the rotor of most single-phase motors to turn in reverse, it is only necessary to switch the two start leads in the circuit. Select one: True False
True PG 163 To reverse the direction of most single phase motors all that is necessary is to switc the two start leads in the circuit.
The rotor windings of a wound-rotor motor circuit are not short-circuited while starting; whereas the rotor windings of a squirrel-cage induction motor are always short-circuited. Select one: True False
True : Note: When all the resistance is removed from the rotor circuit, the last contact shorts the rotor windings and the rotor is a squirrel-cage with a copper winding.
A ? is a device that stores an electrical charge. Select one: a.capacitor b.motor c.rotor d.stator
a.capacitor
Typical applications of ? motors include fairly hard-to-start loads, like refrigerators, air conditioners, air compressors, and some power tools. Select one: a.capacitor b.dual-voltage c.shaded-pole d.split-phase
a.capacitor
A capacitor-start motor operates much the same as a ? , in that it uses a centrifugal switch that opens at approximately 60% to 80% of full-load speed. Select one: a.capacitor-run b.capacitor start-and-run c.shaded-pole d.split-phase
d.split-phase
If a capacitor-start motor is to be reversed often, then a ? switch or foot switch can be used to reverse the current through the start with respect to the run windings. Select one: a.centrifugal b.drum c.rheostat d.winding
drum pg 171
When rotation is not possible because the stator's field and the rotor's field are equal or parallel to one another, the rotor is ? . Select one: a.locked in place b.out of step c.overexcited d.underexcited
locked in place
For the terminal post with links method, the links are used as jumpers to change ? . The links are added by removing the terminal bolt, placing the link over the terminal post, and reconnecting the terminal bolt. Select one: a.motor direction b.the current c.the resistance d.the voltage
motor direction
The function of an OCPD is to protect branch circuit conductors, control equipment, and motors from damage caused by a(n) ? . Select one: a.arc fault b.change in current direction c.overcurrent d.undercurrent
overcurrent
The rotor winding coils of a wound-rotor motor are made up of ? . a.insulated aluminum conductors b.insulated copper conductors c.iron bars d.steel alloy conductors
pg 119the rotor windings of a wound rotor motor consist of coils of insulated copper conductor placed into slots in the rotor. Insulated copper conductors
Brushes may damage the slip rings if they do not have good ? and softness. Select one: a.conductivity b.flexibility c.lubrication d.magnetism
pg 120 Conductivity
When no resistance is applied to the rotor circuit of a wound-rotor motor, the starting torque is about ? of the full-load torque (FLT). Select one: a.50% b.125% c.600% d.3000%
pg 122 125%
A wound-rotor motor regulator is a device that contains high-wattage resistors designed to control the speed of a wound-rotor motor and to operate in variable-speed mode. True False
pg 122 a motor that is controlled by a regulator can have some of the resistors left in the circuit, depending on the speed of the equipment selected by the operator. True
A type S fuse is a ? type fuse. Select one: a.cartridge b.direct-current c.magnetic d.plug
plug
When the dual voltage single-phase motor is reconnected for the higher voltage (115 volts to 230 volts), the current is ? . Select one: a.doubled b.increased by 25% c.reduced by 25% d.reduced by half
reduced by half
Starters usually have one or more timers used to automatically remove ? from the rotor circuit. Select one: a.capacitance b.current c.resistance d.torque
resistance pg 124 see figure 6-9
A ? is a short-circuited winding, which consists of a single turn of copper wire and acts on only a portion of the stator windings. Select one: a.capacitor b.rotor winding c.shaded-pole d.stator winding
shaded pole pg 164
A(n) ? motor is a single-phase AC motor that includes a run winding and a resistive start winding used in applications where starting is easy, such as fans, business machines, machine tools, and centrifugal pumps. Select one: a.capacitor b.induction c.shaded-pole d.split-phase
split-phase
A ? is the fixed, unmoving part of a motor, consisting of a core and windings, that converts electrical energy to the energy of a magnetic field. Select one: a.capacitor b.motor c.rotor d.stator
stator
The rotor windings of a wound-rotor motor can be in either a wye or a delta configuration. Select one: True False
wound rotor rotors are either wye or delta wound to match their stator. pg 119 True