Exam 2 Mech 4

The effective value of AC voltage is also called the __________ voltage. FMS (Frequency Modulated Sinewave) EMS (Electrical Modified Source) RMS (Root Mean Square) All of the above None of the above

RMS (Root Mean Square)

Which of the following is a category of AC motors? Shunt fed Compound wound Three-phase All of the above None of the above

Three-phase

Which of the following is a type of single-phase AC motor? Capacitor-start Permanent-capacitor Split-phase All of the above

All of the above

The first step to test a(n) __________ is to inspect for a bulged case or leaks. rotor stator bearing Capacitor

Capacitor

Which of the following motors has the best speed regulation? DC series DC compound DC shunt All of the above None of the above

DC shunt

The power that is supplied to a load by an AC power source is called __________. reactive power active power apparent power true power

apparent power

An early troubleshooting step is to measure __________, voltage, and speed with the motor running. current resistance winding temperature vibration

current

If a gear attached to a load has more teeth than the gear attached to the motor, the speed of the load will be __________ the speed of the motor. more than less than the same as None of the above

less than

To test a stopped motor, use a multimeter and __________ to check the resistance of the windings, brushes, and insulation. tachometer clamp-on meter encoder megohmmeter

megohmmeter

The most common electrical instrument used to test a DC motor is a(n) __________. multimeter clamp-on meter megohmmeter tachometer

multimeter

A(n) __________ motor has to work harder than it was designed to work, which can lead to premature failure. overloaded under loaded oversized locked rotor

overloaded

When a motor is __________, the speed will decrease drastically from its rated speed. oversized unplugged reversed overloaded

overloaded

AC electricity flowing in a particular wire is called a __________. phase field cycle feed

phase

The windings of a three-phase AC motor are tested by measuring their __________ with a multimeter. capacitance resistance Temperature conductance

resistance

The speed at which the rotor/shaft of an AC motor must rotate to exactly match the speed of the rotating magnetic field is called __________. synchronous speed slip speed overdrive speed All of the above None of the above

synchronous speed

The cost of electrical power is based on __________. the cost of the wire used to transmit the power the amount of loads connected to the power lines the amount of reactive power the number of kilowatts consumed per hour (kWh)

the number of kilowatts consumed per hour (kWh)

Motor efficiency is __________. the ratio of output power to input power the ratio of input power to input current the ratio of output power to input voltage All of the above None of the above

the ratio of output power to input power

Most motors are megger tested at __________ the nameplate voltage rating. half twice three times 10 times

twice

Troubleshooting chart __________ are often listed in order from the most likely to the least likely to cause the symptom. remedies faults tests results

faults

The rate at which the electrical voltage or current cycle repeats is called __________. frequency randomized rate recurrence pulses

frequency

The US Customary units of motor power are __________. kilowatts ft-lb horsepower Volts

horsepower

The insulation resistance to ground should be __________ megaohm per kilovolt, with a 1 megaohm minimum for any megger test. 1 10 100 1000

1

Which of the following is a category of electric motors? DC Motors Universal Motors AC Motors All of the above None of the above

All of the above

Which of the following is a method used to determine motor torque? Prony brake Current measurements Dynamometer All of the above

All of the above

Which of the following is a motor performance characteristic considered when selecting a motor for an application? Torque output efficiency Speed All of the above None of the above

All of the above

Which of the following is a rule of safe dress around electric motors? Wear safety glasses Remove loose items Tie up long hair All of the above None of the above

All of the above

Which of the following is a wiring configuration for a DC motor? series Shunt Compound All of the above None of the above

All of the above

Which of the following is an advantage of using an electric motor? Availability of electrical power Easily controlled with electrical controls Variety of types to choose from All of the above None of the above

All of the above

Which of the following is an application of a DC series motor? Locomotive Crane Hoist Correct! All of the above None of the above

All of the above

Which of the following is an application of a capacitor-start motor? Power tools Pumps Small machines All of the above None of the above

All of the above

Which of the following is an application of a split-phase motor? Fan Centrifugal Pump Business Machine All of the above None of the above

All of the above

The device that is used on a split-phase motor to disconnect the start winding when a predetermined speed has been reached is a __________. Limit switch centripetal switch Pressure switch Centrifugal switch

Centrifugal switch

The advantage of a series configured DC motor is that it can produce __________. constant speed high speed High starting torque variable speed

High starting torque

Which of the following is a disadvantage of a capacitor-start motor? Lower starting torque than a split-phase motor Increased cost due to the addition of a capacitor Increased phase shift between the start and run winding currents All of the above None of the above

Increased cost due to the addition of a capacitor

Electric motors rely on the principle of __________ to convert electrical power into mechanical power. capacitance Inductance resistance gravity

Inductance

Which of the following is an advantage of a split-phase motor? Produces high starting torque Produces low starting torque Is available at a low cost All of the above None of the above

Is available at a low cost

AC motor failures can be __________ or electrical in nature. Physical logical Mechanical Resistive

Mechanical

Megger test voltage is based on the field voltage rating found on the motor __________. Base endbell Nameplate voltage measured with a voltmeter

Nameplate

The S.I. units of torque are __________. nanometers kilometers Neutron-meters All of the above None of the above

None of the above

The relationship between the torque input and output of a gear drive depends on __________. the speed of the motor the size of the motor the direction of rotation All of the above None of the above

None of the above

Which of the following procedures will not reverse the direction of rotation on a DC motor? Reverse the Field Winding Connections Reverse the Armature Connections Reverse the Power Supply Connections All of the above

Reverse the Power Supply Connections

Which of the following is not a method that can be used to reverse the rotation of a split-phase motor? Reverse the power leads Reverse the start winding connections Reverse the run winding connections All of the above None of the above

Reverse the power leads

A resistor that is used to reduce the sparking across the contacts of the centrifugal switch on a capacitor-start motor is called a __________. spark reduction resistor bleeder resistor surge suppressor All of the above None of the above

bleeder resistor

The __________ provide a connection between the power source and the commutator on a DC motor. armature Interpoles brushes field windings

brushes

A quick test to determine if a motor's torque demand is too high is to measure the motor __________. current voltage resistance Inductance

current

If a motor is too heavy for you to move by yourself, you should __________. get someone to help you move it forget about it take the rest of the day off move it anyway

get someone to help you move it

The primary purpose of the interpoles is to __________. increase motor speed help reduce sparking between the commutator and the brushes make current flow in only one direction provide a connection between the power source and the commutator

help reduce sparking between the commutator and the brushes

Field windings should have about 1 to 10 ohms of resistance end to end, sometimes slightly higher. Resistance should be __________ to the frame and to other windings. infinite less than an ohm 1000 ohms low

infinite

Torque is developed in an electric motor because of __________. gravity inertia interaction of different magnetic fields kinetic energy

interaction of different magnetic fields

The amount of torque that a motor must generate at its shaft to drive the device it is driving is called the __________. opposing force load regulator All of the above None of the above

load

Disconnect the motor leads from the incoming power at the motor junction box before performing a(n) __________ test. voltage current Speed megohmmeter

megohmmeter

The rotational speed of a motor is measured in units of __________. resolutions per minute turns per second revolutions per minute All of the above None of the above

revolutions per minute

A DC __________ motor is one that has the field windings connected in series with the armature Compound series Shunt servo

series

DC motor field windings are subject to __________ in a winding, an open winding, and individual windings shorted to the motor frame or to other windings. contraction shorts Heating expansion

shorts

The waveform that is produced by alternating current looks like a __________. sea wave sine wave sawtooth wave square wave

sine wave

The difference between the synchronous speed and the actual speed at which an AC motor will run is called __________. slop slip differential All of the above None of the above

slip

AC motor overloading causes high __________ current and high temperature, which causes the winding insulation to fail. rotor stator armature Interpole

stator

The __________ is the stationary winding of the electric motor. stator rotor shaft armature

stator

The fourth color band on a resistor represents __________. the multiplier the division factor the second digit of the resistance value the tolerance of the resistance value

the tolerance of the resistance value

A power factor of 100% is called __________. unity power factor absolute power factor leading power factor All of the above None of the above

unity power factor