207 Single-Phase Motors

If you have problems with a split-phase motor, you should test both windings for _____________, _____________, and ____________.

GROUNDS, OPEN CIRCUITS, SHORT CIRCUITS Ref: 2.56

The brushes on a repulsion-start motor are never positioned on the brush yoke line for _____________, because the motor cannot develop any starting torque.

HARD NEUTRAL Ref: 4.33

Wedge-shaped brushes are used when you need to find the position of _____________.

HARD NEUTRAL Ref: 4.37

A repulsion motor can be reversed by shifting the brushes to the other side of ______________.

HARD NEUTRAL Ref: 4.49

What are the names of the two kinds of neutral planes in a repulsion motor?

HARD, SOFT Ref: 4.10

If necessary, you can substitute by using a capacitor with a _____________ voltage rating than the original.

HIGHER Ref: 3.69

A reversible capacitor-run motor will not start without a capacitor in the circuit, because the windings are ____________.

IDENTICAL Ref: 3.53

Does the compensating winding in a repulsion motor increase or decrease the power factor?

INCREASES IT Ref: 4.53

A(n) ____________ reading on an ohmmeter indicates an open circuit. A(n) _____________ reading indicates the winding is not open.

INFINITE; LOW Ref: 2.65

A(n) ____________ must be established in a capacitor-start motor to produce the starting torque.

ROTATING MAGNETIC FIELD Ref: 3.18

In an induction motor, a potential difference is induced in the ____________ by the ___________ of the stator.

ROTOR; MAGNETIC FIELD Ref: 1.29

What is the name for the rotating part of a motor? For the stationary part?

ROTOR; STATOR Ref: 1.01

The end plate bearings support the ____________ and keep it centered within the ___________.

ROTOR; STATOR Ref: 1.05

Are the coils in a stator winding wound in the same direction when the motor is manufactured, or in opposite directions?

SAME DIRECTION Ref: 2.24

In dual-voltage split-phase motors, the coils are connected in ___________ for 240 V, and in ___________ for 120 V.

SERIES; PARALLEL Ref: 2.54

A split-phase motor can be made to run as a capacitor-start motor by connecting a capacitor in ____________ with the ____________ winding.

SERIES; START Ref: 3.13

The commutator in a repulsion motor connects the armature windings to each other through ____________.

SHORTED BRUSHES Ref: 4.25

Which winding normally has higher resist ance in a split-phase motor?

START Ref: 2.19

In a split-phase induction motor, the wire in the _____________ winding is smaller than the wire in the ____________ winding.

START; RUN Ref: 2.09

The brushes in a repulsion motor are used only for ____________.

STARTING Ref: 4.26

One coil pitch of a coil is defined as the number of ___________ a coil spans.

STATOR SLOTS Ref: 2.291

A single-phase induction motor can be made self-starting by adding a second _____________.

STATOR WINDING Ref: 2.05

The ______________ winding of a repulsion motor is identical to the ____________ winding of a split-phase motor.

STATOR; RUN Ref: 4.60

Slip speed is the difference between a motor's ____________ speed and its ____________ speed.

SYNCHRONOUS; OPERATING Ref: 1.07

How many coils are required in a consequent-pole motor having a total of four poles?

TWO Ref: 2.39

A capacitor-start capacitor-run motor having two different values of capacitance is called a(n) ____________ motor.

TWO-VALUE CAPACITOR Ref: 3.48

A capacitor for use in a 120 V motor must be rated for _______________ V. a. 75 to 130 b. 130 to 150 c. 175 to 225 d. 250 to 300

b. 130 to 150 Ref: 3.10

According to Fig. 1-3, all standard motors with frame number 184T have a maximum base width of ____________ in. a. 7 b. 9 c. 10 1/2 d. 11 3/8

b. 9 Ref: 1.10, Fig. 1-3

Which of the following is not part of a rotor? a. Core b. End plates c. Shaft d. Squirrel cage

b. End plates Ref: 1.02

How many coils are required in a consequent-pole motor having a total of four poles? a. One b. Two c. Three d. Four

b. Two Ref: 2.39

The brushes in a repulsion motor are connected to ____________. a. an outside power source b. each other c. the commutator d. the load

b. each other Ref: 4.04

If a winding makes electrical contact with the stator case, the winding is _____________. a. closed b. grounded c. open-circuited d. short-circuited

b. grounded Ref: 2.57

If you must substitute one capacitor for another, the best choice is one with a _______________. a. higher capacitance b. higher voltage rating c. lower capacitance d. lower voltage rating

b. higher voltage rating Ref: 3.69

A megohmmeter reading of 1 Mohm or more means the winding are ___________. a. grounded b. not grounded c. shorted d. not shorted

b. not grounded Ref: 2.59

A short circuit occurs in a capacitor when the ______________ material breaks down.

DIELECTRIC Ref: 3.60

Which connections must you reverse to reverse the direction of rotation in a split phase-motor?

EITHER START OR RUN Ref: 2.14

What kind of capacitor has polarity markings, and must not be used in ac circuits?

ELECTROLYTIC Ref: 3.08

Whenever you must replace brushes, use brushes that are _____________.

EXACT DUPLICATES OF THE ORIGINALS Ref: 4.44

In a dc generator, the brushes conduct current to the _____________. In a dc motor, they conduct current to the ____________.

EXTERNAL LOAD; ARMATURE Ref: 4.15

To calculate the synchronous speed of an induction motor, you need to know the _____________ of the power supply and the ______________ in the motor.

FREQUENCY; NUMBER OF POLES Ref: 1.51

A standard split-phase motor is used for applications that require _____________ starting and ____________ operating periods.

FREQUENT; LONG Ref: 1.59

What device in a power line is the short-circuit protective device for a motor?

FUSE or CIRCUIT BREAKER Ref: 3.28

AC motors are designed to operate at +/- ____________% of their rated potential difference and +/- ___________% of their rated frequency .

10; 5 Ref: 1.11

A dual-voltage motor can operate on either _____________ V or _____________ V.

120, 240 Ref: 3.45

In a split-phase motor, any two ____________ poles must have the opposite magnetic polarity.

ADJACENT Ref: 2.22

What cools the windings in an open motor?

AIR Ref: 1.14

Decreasing the rotor speed in a two-speed capacitor-run motor is accomplished by adding a(n) ____________.

AUXILIARY WINDING Ref: 3.55

A brush-riding motor usually has a(n) ____________ commutator. A brush-lifting motor usually has a(n) ____________ commutator.

AXIAL; RADIAL Ref: 4.06

A(n) _____________ can give the same symptoms as worn or dry bearings.

BENT ROTOR SHAFT Ref: 2.82

What is an indication that a motor shaft has overheated?

BLUE COLOR Ref: 2.75

If one capacitor in a two-capacitor motor is defective, should you replace both capacitors, or only the bad one?

BOTH Ref: 3.75

Lap-wound armatures without equalizer connections must have as many _____________ as _____________.

BRUSHES; POLES Ref: 4.67

A(n) ____________ is a device that can store electrical charge.

CAPACITOR Ref: 3.03

A short-circuiter works by ____________ force when the armature reaches a predetermined speed.

CENTRIFUGAL Ref: 4.19

What devices may be used for disconnecting the start winding in a single-phase induction motor?

CENTRIFUGAL SWITCH, MAGNETIC RELAY, THERMAL RELAY Ref: 1.53

A(n) ____________ pole forms as a consequence of the formation of another magnetic pole.

CONSEQUENT Ref: 2.38

How long can most motors run without overheating?

CONTINUOUSLY Ref: 1.18

In a split-phase motor, the start-winding current ____________ the run-winding current, but it ____________ the applied potential difference.

LEADS; LAGS Ref: 3.19

A permanent-split capacitor motor has a(n) ____________ instead of a centrifugal switch.

LOW-VALUE CAPACITOR Ref: 3.49

Which rotates faster in an induction motor, the magnet or the disk?

MAGNET Ref: 1.21

Can a symmetrically wound single-phase induction motor start by itself?

NO Ref: 1.24

If two identical windings are connected to a single-phase source, will their combined magnetic field rotate?

NO Ref: 1.38

To change the speed of a split-phase motor, you must change the ____________.

NUMBER OF POLES Ref: 2.40

Smoke from a motor may be caused by ______________, ______________ or ______________.

OVERLOAD, SHORTED WINDINGS, FAULTY CENTRIFUGAL SWITCH Ref: 3.65

For starting a split-phase motor, the run and start windings are connected in ____________.

PARALLEL Ref: 2.08

An axial commutator has bars ____________ to the motor shaft. A radial commutator has bars _____________ to the shaft.

PARALLEL; PERPENDICULAR Ref: 4.03

In a motor or generator, how far must a conductor move in order to complete one cycle?

PAST TWO POLES Ref: 1.48

The number of brushes riding on the commutator ordinarily depends on the number of ____________ in the motor.

POLES Ref: 4.30

Before you replace a motor, make sure the correct ____________ is applied.

POTENTIAL DIFFERENCE Ref: 4.69

Before disconnecting a capacitor from a motor, you must disconnect the ______________.

POWER SUPPLY Ref: 3.62

Single-phase induction motors are noisy, because the rotating magnetic field ____________.

PULSATES Ref: 1.37

Can a standard motor made by one manufacturer be replaced by the same standard motor made by another manufacturer?

YES Ref: 1.08

What is the synchronous speed of a six-pole motor running on power at 50 Hz? a. 1000 rpm b. 1200 rpm c. 6000 rpm d. 7200 rpm

a. 1000 rpm Ref: 1.51

What is the NEMA designation for a motor having normal starting torque, normal starting current, high breakdown torque, and low slip? a. A b. B c. C d. D

a. A Ref: 1.18

Which of the following provide(s) thermal overload protection in some capacitor-start motors? a. Bimetallic strip b. Circuit breaker c. Fuse d. All of the above

a. Bimetallic strip Ref: 3.27

Which of the following is not a method used for identifying the motor leads in a single-phase motor? a. Counting the number of stator poles b. Inspecting the stator windings c. Measuring the resistance of each winding d. NEMA color code

a. Counting the number of stator poles Ref: 2.16 to 2.20

What is the purpose of the capacitor in a reversible capacitor-run motor? a. To change the phase angle b. To maintain the phase angle c. To prevent the magnetic field from rotating d. To separate the windings

a. To change the phase angle Ref: 3.53

The service factor of a motor is defined as the ____________. a. allowable overload b. difference between synchronous and operating speeds c. kind of power the motor uses d. length of time it can operate continuously

a. allowable overload Ref: 1.07

Repulsion motors _____________. a. are reversible b. have low starting torque c. run at only one speed d. all of the above

a. are reversible Ref: 4.49

To decrease the speed of a repulsion motor, you move the brushes ____________. a. away from the optimum position b. closer to the optimum position c. in a counterclockwise direction d. toward hard-neutral

a. away from the optimum position Ref: 4.49

The maximum torque a motor can produce without an abrupt decrease in speed is called its ___________ torque. a. breakdown b. full-load c. locked-rotor d. pull-up

a. breakdown Ref: 1.07

Two 120 V capacitors connected in series have a combined voltage rating of ______________ V. a. 60 b. 120 c. 240 d. 360

c. 240 Ref: 3.71

What governs the speed of an induction motor? a. Frequency of the power supply b. Number of poles c. Both a and b above d. Neither a nor b above

c. Both a and b above Ref: 2.40

Which kind of motor has one or more short-circuited auxiliary windings that are displaced from the main winding? a. Capacitor-start motor b. General-purpose motor c. Shaded-pole motor d. Special-purpose motor

c. Shaded-pole motor Ref: 1.06

If the brush yoke has three lines, the line in the center indicates ____________. a. a clockwise rotation b. a counterclockwise rotation c. hard neutral d. soft neutral

c. hard neutral Ref: 4.33

If two identical windings are connected in parallel to an ac source, the currents in the windings will both _____________ the potential difference. a. be in phase with b. cancel c. lag d. lead

c. lag Ref: 1.40

If a capacitor motor has difficulty starting or has poor starting torque, the trouble may be _____________. a. faulty capacitor switch b. grounded windings c. loose rotor bars d. overload

c. loose rotor bars Ref: 3.63

Any two adjacent poles have the opposite polarity ____________. a. except in series-connect motors b. if the motor has an odd number of poles c. no matter how many poles the motor has d. unless one is a consequent pole

c. no matter how many poles the motor has Ref: 2.22

If the end shafts of a rotor turn blue, it is an indication of ___________. a. burring b. freezing c. overheating d. scoring

c. overheating Ref: 2.75

In order to complete one ac cycle, a conductor must move ____________. a. past a north magnetic pole b. past a south magnetic pole c. past two magnetic poles d. through 360°

c. past two magnetic poles Ref: 1.48

All the following are open motors, except the ____________ motor. a. dripproof b. splashproof c. waterproof d. weather-protected

c. waterproof Ref: 1.15

If you suspect a capacitor is defective, what should you do before you test it? a. Discharge the capacitor through a resistor b. Disconnect the capacitor leads c. Disconnect the power supply d. All of the above

d. All of the above Ref: 3.62 and Warning

If a motor has been taken apart and reassembled, how is the hard-neutral position relocated? a. By looking for the centerline on the brush yoke b. By turning the motor to see if it starts c. By using the original brushes d. By using wedge-shaped brushes

d. By using wedge-shaped brushes Ref: 4.37, 4.38

Which of the following ohmmeter readings indicates an open circuit in a split-phase motor winding? a. Zero b. Low reading c. Mid-range reading d. Infinite reading

d. Infinite reading Ref: 2.65

Noise and high temperatures indicate ____________. a. a bent rotor shaft b. dry bearings c. worn bearings d. any of the above

d. any of the above Ref: 2.81 to 2.82

Most repulsion-start motors are designed to reverse the direction of rotation by _____________. a. adding more turns to the winding b. adding poles c. centrifugal force d. moving the brushes

d. moving the brushes Ref: 4.31

The compensating winding in a compensated repulsion motor ______________. a. is larger than the main winding b. is the same size as the main winding c. lowers the power factor d. raises the power factor

d. raises the power factor Ref: 4.53

A single-phase induction motor can be made self-starting by adding a ____________. a. centrifugal switch b. second rotor c. second set of magnetic poles d. second stator winding

d. second stator winding Ref: 2.05

A split-phase motor can be made to run as a capacitor-start motor by connecting a capacitor in _____________ with the _______________ winding. a. parallel; run b. parallel; start c. series; run d. series; start

d. series; start Ref: 3.13

A capacitor is made to ______________ an electric charge. a. decrease b. dissipate c. increase d. store

d. store Ref: 3.03