AIRC 1040
Reactive power of an inductor has the symbol of _____.
VARS
Single-phase motors are generally protected with a small ____ reset overload.
automatic
The rotating magnetic field of a shaded-pole induction motor is created by a ____ wound around one side of each pole piece.
coil
The ____ contains a coil of a few turns of large wire, and a set of normally open contacts.
current relay
The shaded-pole motor contains a start winding or centrifugal switch.
false
Most starters use three transformers connected in an open delta.
false. two transformers
Unit 12: Shaded-pole motors are commonly wound as ____ motors.
four or six pole motors
which of the following are the three factors in determining how much capacitance a capacitor will have?
1 the surface area of the plates 2 the distance between the plates 3 the type of dielectric material used between the plates
Unit 15: Which of the following is a determining factor in the amount of torque produced by an AC induction motor?
1. the strength of the magnetic field of the stator 2. the strength of the magnetic field of the rotor 3. the phase angle difference between stator and rotor flux
Which of the following is a determining factor in the amount of induced voltage?
1.the strength of the magnetic field 2.the number of turns of wire cut by the magnetic field. 3.speed of the cutting action.
Overload units are designed to open their contacts when the motor current reaches ____ of full-load current.
115% to 125%
The phase-angle difference between current in the run winding and current in the start winding of a resistance-start induction-run motor is generally ____ degrees.
35 to 45 degrees
A starting relay is used to disconnect the start windings when the motor has reached about ____ of its full speed.
75%
Unit 8: The ____ is designed to be used for a short period of time only.
AC electrolytic capacitor
The solder-melting type of overload relay has a set of small ____ that are intended to interrupt the current flow in the control circuit only.
Auxiliary contacts
Chapter 26:The solid-state relay can be used to replace almost any hot-wire relay.
False
Small reed relays are probably the most common method for controlling a solid-state relay.
False
The amount of voltage necessary to energize the coil of a potential relay is smaller than line voltage.
False
The bimetal type of overload operates very differently from the solder-melting type. T/F
False
The bimetal type of overload unit is used to a large extent on commercial and industrial air conditioning units. T/F
False
The simplest of the AC loads is a circuit that contains only pure inductance. T/F
False
The single-phase motors used in air conditioning systems are generally one of three types.
False ( it uses one of two types)
Capacitors can be tested for a short with a voltmeter.
False ( they can be tested with an ohmmeter)
A capacitor can be made by separating two metal plates with a conducting material.
False (A capacitor can be made by separating two metal plates with an insulating material)
Interlocking is used to cause some function to happen before some other function occurs. T/F
False (interlocking is used to cause some function to happen until some other function occurs)
The shading coil is a large loop of steel wire or a steel band. T/F
False (its a large loop of copper wire)
The voltage and current in a pure-resistive circuit are out of phase with each other.
False (the voltage and current in a pure resistive circuit are in phase with each other)
The contacts of the centrifugal switch are connected in parallel with the start winding.
False (they are connected in series)
Capacitors are rated in units called the ____.
Farads
The unit of inductance is the _____.
Henry
To properly test the ____, an ammeter should be used to make certain the start contact opens and disconnects the start winding.
Hot Wire Relay
The total current-limiting effect is called _____.
Impedance and is symbolized by the letter Z
When a magnetic field continually changes magnitude and direction, a voltage is continually being induced in the coil. This voltage is called _____ voltage.
Induced
Circuits are generally considered to contain _____ when any type of load that contains a coil is used.
Inductance
The ____ has greatly increased in popularity for use in the air conditioning field over the past years.
Permanent split capacitor motor
The amount of resistance compared with the inductive reactance determines the _____ of the coil.
Quality
Unit 7: The current-limiting property of an inductor is called _____.
Reactance
The direction of rotation of a ____ can be reversed by changing the start winding leads or the run winding leads, but not both.
Split phase motor
A rotating magnetic field can be produced with two separate phases.
True
A starting relay is located away from the motor.
True
An inductive circuit contains an inductor or coil as the load instead of a resistor. T/F
True
Capacitors have the ability to supply an almost infinite amount of current.
True
Each phase of a three-phase motor should be protected by an overload relay. T/F
True
Eddy currents are currents induced in the core material by the magnetic field of the coil. T/F
True
One disadvantage of the hot-wire relay is that it must be permitted to cool after each operation.
True
Power factor is important because utility companies charge industries large penalties for a poor power factor. T/F
True
Some dual-voltage motors will contain two start windings as well as two run windings.
True
The relay is a magnetically operated switch. T/F
True
The relay operates on the solenoid principle. T/F
True
The shaded-pole induction motor is considered to be nonreversible. T/F
True
Unit 22: Overload relays will trip faster in hot weather than they will in cool weather. T/F
True
When testing the current relay, an ohmmeter can be used to check the continuity of the contacts.
True
Reactance is given the electrical symbol ____.
X
The symbol for reactance is _____
X
The plunger-type of solenoid is generally used with relays that use ____.
double-break contacts
All relays use opto-isolation to control the output.
false
Most overload relays are operated by ____.
heat
Inductors are measured in units called the ____.
henry
Since the overload unit must be sensitive to motor current, the heater of the overload relay is connected ____.
in series with the motor
The symbol X L stands for _____.
inductive reactance
A solenoid is an electrical device that converts electrical energy to ____.
linear motion
Motor starters generally contain auxiliary contacts as well as ____.
load contacts
The shaded-pole motor has a low starting torque and ____.
running torque
AC relays used shading coils on the ____ to prevent contact chatter.
shading coil
The solid-state relay is a device that has become increasingly popular for ____.
switching applications
Some solid-state relays are designed to be used as ____.
time delay relays
Solid-state relays can be used to control either a DC load or an AC load.
true
The current of a capacitive circuit is in direct opposition to the current of an inductive circuit.
true
The energy of a capacitor is stored in the dielectric.
true
Unit 11: Some ____ are equipped with a separate starting capacitor to improve starting torque.
Permanent split capacitors motor
The ____ operates by sensing an increase in the voltage developed in the start winding when the motor is operating.
Potential Relay
Volt-amperes-reactive is used to measure the _____ in a pure inductive circuit.
The reactive power (VARS)
The shaded-pole induction motor is another type of AC single-phase motor used to a large extent in the air conditioning field. T/F
True
In a wye connection, the line current is greater than the phase current by a factor of the square root of 3.
false. this is for the delta connection
The solder-melting type overload relay has two separate sections: the heater section and the contact section. T/F
True
The advantage of the relay is ____.
control
Current lags voltage by 90 ° in a pure inductive circuit. T/F
current lags behind the voltage by 90 degrees
In an AC circuit that contains only inductance, the current is limited only by the value of ____.
inductive reactance
The direction the magnetic field moves across the face of the pole piece ____ the side of the pole piece that has the shaded coil.
is determined by
In a pure inductive circuit, current _____.
lags behind the voltage by 90 degrees.
Most service technicians test a three-phase motor with a(n) ____.
ohmmeter
The relays that use optical coupling are referred to as being ____
opto isolated
The oil-filled capacitor is made with two metal foil plates separated by ____.
paper
The greater the ____ between rotor and stator flux, the less torque that is developed by the motor.
phase angle between rotor and stator flux
In a pure-____ circuit, the voltage and current are in phase with each other.
resistive
Solid-state relays intended for use as AC controllers have a ____ connected to the load circuit in place of a power transistor.
triac
Interlocking is used to prevent one contactor being energized while some other contactor is energized.
true
Many solid-state relays have a feature known as zero switching.
true
Motors intended for use with part winding starting contains two separate stator windings.
true
Often it is necessary to reduce the inrush current during the starting period of large motors.
true
Solid-state relays are sealed against dirt and moisture.
true
The shaded-pole motor contains a standard squirrel-cage rotor.
true
VARs is often referred to as ____.
volt-amps reactive
In an induction motor, the current flow in the rotor is produced by induced ____ from the rotating magnetic field of the stator.
voltage
Unit 23: The term relay is often used to describe any type of electronically operated switch. T/F
False (a relay is a magnetically operated switch)
The control voltage for most solid-state relays ranges from about ____.
3-32 volts
____ and common digital meters do not supply enough voltage to test the dielectric at rated voltage.
Ohmmeter
Many manufacturers of ____ will identify one terminal with an arrow, a painted dot, or by stamping a dash in the capacitor can.
Oil filled capacitors
The ____ is an electronic component known as a thermistor.
Solid state relay
The shaded-pole induction motor is popular because of its ____.
of its simplicity and long life
