Single Phase Motors TPC
In synchro transmitters and receivers, stator coils serve as the ____________ windings of a variable transformer.
...
Proper belt slack halfway between the hubs of a belt drive is between _________ and _________ in.
1/2; 3/4
The maximum allowable end play in a 1 hp motor is
1/32 in
A capacitor rated at 200 microfarads is still usable if its measured capacitance is at least _________ microfarads.
160
Hysteresis motors will run on frequencies ranging from _________ to _________ Hz.
25; 2000
In ac circuits, general-use ac snap switches may be used for controlling a motor rated at up to __________ hp and __________ V.
2; 300
An inductor motor has 48 rotor teeth. How many cycles of the power supply are required for the rotor to make one revolution?
48
A split-phase motor uses a centrifugal switch to take the start winding out of the circuit when the motor reaches approximately ________% of synchronous speed.
75
A servomechanism has the abbreviations CX and CT on it. What do these mean?
Control transmitter, control transformer
The service factor of a motor indicates how much the motor may be overloaded when operating at its rated potential difference and
Frequency
Which class of motor insulation allows for the greatest maximum temperature for continuous motor service?
H
Which of the following problems may cause low starting torque in a capacitor motor?
Loose rotor bars
Many electric motors are manufactured according to standards set by
NEMA
Industrial servosystems use the basic principle of the ____________ to position the shafts of mechanical and hydraulic devices.
Wheatstone brid
A typical size universal motor used in an appliance requires ____________ replacement after 200 to 1200 hours of service, large motors after 3000 hours or so.
carbon brush
A servomotor operates when the
control field is energized
The part of a synchro control system that supplies an ac signal from its rotor is the
control transformer
When an unexcited synchronous motor fails to reach synchronous speed and continues to run as an induction motor, it
draws more than its rated current
You can reverse the direction of rotation in a split-phase motor by reversing the connections to
either winding but not both
The best way to maintain torque in a universal motor running at low speed is to use a(n)
electronic controller with an SCR
If the circuit breaker trips when you start a capacitor motor, the cause may be a(n)
faulty centrifugal switch
The grounding conductor connected to a grounding plug is
green
A distinguishing characteristic of a universal motor is its
high power output per pound of weight
The distinguishing characteristic of a synchronous motor is that it runs ____________ the rotating magnetic field.
in step with
In larger synchro units, a mechanical device called a(n) ____________ is used to produce a retarding action on the rotor when a receiver unit is first turned on.
inertia damper
An open winding in a split-phase motor is indicated by an ohmmeter reading of
infinity
The NEC requires that the frame of a stationary motor be grounded if
it is supplied by metal-enclosed wiring
To overcome power lost due to hysteresis and eddy currents, an ac series motor frame is made from ____________ iron, while the field winding is made with fewer turns than that of a dc series motor.
laminated
Some motor controllers are rated for both full-load current and ____________ current.
locked-rotor
To determine whether a winding in a split-phase motor is grounded, you should use a(n)
megohmmeter
If you connect a dc shunt motor to an ac power source, the
motor runs inefficiently
On a motor nameplate, the NEMA designation "A" indicates a
normal starting current
In order to change the speed of an induction motor, you must either change the frequency of the power supply or change the
number of poles
A manual single-phase motor starter has
one or two poles
A(n) ____________ motor is one that has openings that allow air to pass through and cool the
open
In order for a dual-voltage motor to run on 120 V instead of 240 V, its running windings must be connected in
parallel
You can mechanically reverse a shaded-pole motor by removing the end plates of the motor and ____________ the stator poles.
physically reversing
The purpose of the long time-lag thermal cutout on a dual-element fuse is to
prevent unnecessary shutdowns
A servo is any device or system of devices that controls a physical quantity in relation to a
reference value
The magnetic pole that projects above the surrounding stator core in a shaded-pole motor is known as the _________ pole.
salient
A synchro rotor that has two large poles connected by a crossbar in its core is called a _________ rotor.
salient-pole
In synchro transmitters and receivers, stator coils
serve as the secondary windings
Synchros can control an amplifying device called a ____________ to move a large load.
servomechanism
Most single-phase induction motors are made with two stator windings: a run winding (main winding) and a ____________ winding (auxiliary winding).
start
The stationary part of a single-phase motor is called the ____________. The rotating part of the motor is called the rotor.
stator
Two capacitors connected in series have a combined voltage rating equal to the _________ of their individual ratings.
sum
The speed of a multispeed motor is adjusted by using a
tapped field winding
To provide thermal overload protection, some capacitor motors have a bimetallic ____________ connected in series with the incoming line and mounted on the motor.
thermostat
Noise indicates either electrical or mechanical problems with a motor. One method of distinguishing one from the other is to shut off the power and ____________ the rotor ____________.
turn; by hand
An amplidyne generator has _________ set(s) of brushes on the commutator.
two
The name "squirrel cage" comes from the ____________ of the rotor winding.
wheel-like appearance
A large amount of movement in any direction by a motor's shaft is a sign of a
worn bearing
