Written test 2 100 questions Flashcards
1
Q
which of the following voltages are not safe for a 208-V motor to operate? a 170 volts h 220 volts c 238 volts d bath a and c
A
d bath a and c
2
Q
if the voltage supplied to the motor is well below the motor rated voltage, the current draw will be it should be
A
higher than
3
Q
The voltage tolerance of a standard electric motor is
A
+15%-15%
4
Q
locked-rotor amperage is normally ________times as great as the nun-load amperage
A
three
5
Q
Why are explosion-proof motors not normally used on standard equipment?
A
They are too expensive.
6
Q
motor that should be used in a potentially wet area is a(n)___ motor
A
Drip proof
7
Q
When referring to motors, to what does the “insulation class” relate?
A
the normal operating temperature of the motor
8
Q
A sleeve bearing would typically be used in a motor that operates with a
A
light load and where noise is a factor
9
Q
A slotted screw at the bottom of the bearing housing is called a
A
relief plug
10
Q
A direct-drive motor is usually connected to a load with a
A
coupling
11
Q
Grounding straps are required on resilient mounted motors to
A
ground the motor in case of winding failure
12
Q
The width of a drive belt is classified as
a. large or small
b. narrow or wide
c. A or B
d. 1 or 2
A
c. A or B
13
Q
The alignment of a motor and the driven mechanism must be done at room temperature and
A
at operating temperature
14
Q
A motor can burn out if the supply voltage is either too high or too low
True or Fales
A
True
15
Q
One method a technician can employ to check a motor is to take amperage readings of a motor
(both on and after start-up) and compare them to the motor’s nameplate
on start-up and
a. True
b. false
A
True
16
Q
The delta transformer has been popular in some locations in the past
a. True
b. False
A
A
17
Q
- A drip proof motor is designed to prevent any lubricating oil from leaving any of the bearings
a. True
b, False
A
False
18
Q
When oiling a permanently lubricated motor, a 20-weight, non-detergent motor oil should be used
a. True
b. False
A
False
19
Q
Regardless of the type of motor or application, the motor bearings require yearly lubrication.
a. True
b. False
A
True
20
Q
There is a definite relationship between the speed of the motor and the speed of the blower
a. True
b False
A
True
21
Q
A motor’s speed is determined by _____
A
number of motor poles
22
Q
Start wingdings are placed ____
with the run winding
A
slightly out of phase
23
Q
The start windings have
A
more turns than the run windings
24
Q
A split-phase has a___
winding and a___winding
A
start, run
25
when a general duty split phase motor reaches a approximately 75% of its operating speed, the start winding is de-energized by a
centrifugal switch
26
A split-phase motor that has a current relay and a start capacitor is called a(n)___
motor
Capacitor Start, Induction Run (CSIR)
27
When a Capacitor Start Induction Run (CSIR) motor is running and up to speed, what is the total capacitance act on the motor? (Assume the run capacitor is 5 micro farads and the start capacitor is 20 micro-farads, if present.)
5 micro-farads
28
A permanent split capacitor (PSC) motor that is running and up to speed will have the start winding ______
energized
29
When a Capacitor Start, Capacitor Run (CSCR) motor initially starts, what is motor? (Assume the run capacitor is 5 microfarads and the start capacitor is 20 microfarads, if present.)
25 microfarads
30
Capacitors wired in series with the starting winding provide a(n)
greater starting torque
31
The shaded pole motor_
has little starting torque
32
Three phase motors have
run windings only
33
A current magnetic relay opens and closes its contacts based on the
Current in the start winding
34
The starting device usually used on single phase, fractional horsepower motors requiring low starting torque is the
current relay
35
The positive temperature coefficient resistor start device is a type of
variable resistor
36
A permanent split-capacitor motor has a
run capacitor only
37
The magnetic fields generated in the rotor and stator of a motor causes the rotor to be pushed around the shaft.
a. True
b. False
False
38
The heavier the load on an operating motor, the greater the amount of slip.
a. True
b. false
True
39
In order to change the direction of rotation of a split-phase motor, the technician must change the direction of current flow through the start winding.
a. Truc
b. False
True
40
The centrifugal switch mounted on the shaft of a split-phase motor has a normally closed contact
a. True
b. False
True
41
the contact() in a potential type starting relay arc normally closed
a. True
b. False
True
42
Once the start winding and the start capacitor have been removed for the circuit, the motor will continue to operate with only the run winding energized.
a. True
b. False
True
43
The microfarad rating of the run capacitor is much lower than that of the start capacitor for any given motor
application
a. True
B.false
true
44
44. A Capacitor Start Capacitor Run (CSCR) motor that is wired with a potential relay will have the start winding energized when the relay's contacts open.
a. True
b. False
True
45
The contact(s) in a current type starting relay are normally closed
a. True
b. False
False
46
The resistances of the windings in a three phase motor are all equal
a. True
b. False
True
47
winding when energized, will generate a magnetic field as there will be current flowing through it.
A. True
b. False
True
48
A motor that has copper bars in the rotor is classified as a(n)_______type.
a. True
b. False
False
49
The difference between synchronous speed and full load speed is called slip
a true
b. False
True
50
The coil of a potential relay has low resistance
a. True
b. False
true
51
Charging a refrigeration system refers to
adding refrigerant to a system
52
Refrigerant in vapor form is normally put into the system through the
suction line
53
When charging a system with vapor refrigerant from a refrigerant cylinder, the cylinder will become
Cold
54
Refrigerant in liquid form is normally put into the system through the
liquid line
55
When charging liquid refrigerant from a single valve supply cylinder, the cylinder is placed
upside down
56
A graduated cylinder charging device is a device that
a. measures refrigerant by volume for precise refrigerant charging
b. has a compensation dial for adjusting for the temperature of the refrigerant
c. often has a heater to keep the refrigerant temperature from dropping when refrigerant is released into the system
d. All of the above.
D all the above
57
If 22 oz of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 24 lb. 12 oz. before any is added, what will be the supply cylinder weight after the system has been charged?
23 lb 6 0z.
58
If 30 oz of refrigerant are to be added to a refrigeration system and the supply cylinder weighs 26 lb. 4 az. before any is added, what will the supply cylinder weigh after the system has been charged?
24 lb 6 oz
59
The factory charge in a split system, using R-22, shows 6 Ib. 8 oz. in the outdoor condensing unit and 2 oz in the evaporator. The 3/8" liquid line contains 0.48 oz. per foot and the 7/8" suction line contains 0.10 oz per foot. The refrigerant lines are 30' long. What is the correct refrigerant charge for this system?
7 lb 11 oz
60
If a critically charged refrigeration system is over charged, which of the following is a likely result?
a. Increased cooling capacity
b. Reduced compressor discharge temperature
c. Increased system efficiency
d. Increased operating pressures
. Increased operating pressures
61
Fractionation occurs when
some of a blended refrigerant evaporates or condenses before the rest of the blend
62
When charging a refrigeration system with a near-isotropic mixture, what must be done to prevent liquid from entering a system
Charge as a liquid through the low side using a restrictor
63
When adding refrigerant in vapor form to an operating refrigeration system, the refrigerant rust be added to the low-pressure side of the system
True
64
Missing 65
Missing 65
65
66. When the system pressures are lower than the pressure in the refrigerant tank, such as when the system has just been evacuated or if the system is out of refrigerant, refrigerant can be added to both the high and low pressure sides of the system.
a. True
b False
true
66
If the tank is a reusable tank, there are no check valves and system refrigerant can enter the tank as long as the system pressure is higher than the pressure in the tank
a. True
b. False
True
67
The quickest method to charge a system is to charge only vapor
a. True
b. False
False
68
When adding refrigerant in liquid form into the high-side of the system, the system motor/compressor assembly running
a. True
b. False
False
69
Using a restrictor, liquid refrigerant can be charged into the low-side of the system with the system operating.
a. True
b. False
True
70
One good feature of an electronic charging scale is that it counts upward as refrigerant is removed, to tell the technician how much refrigerant was used
a. True
b. False
True
71
A manufacturer's charging chart may be used when available to determine the correct charge for a system
a. True
b. False
True
72
Glide is the range of temperatures/pressures in which a blended refrigerant will condense
a True
b.False
True
73
Refrigerant in vapor form is added to an operating system through the High Pressure side of the system
a True
b. False
False
74
As refrigerant vapor is removed from a supply cylinder, the pressure in the supply cylinder will fall.
a True
b False
True
75
The king valve is used to help technicians perform a number of tasks including taking pressure readings on system and trapping all of the system refrigerant in the receiver to perform system service.
a True
b. False
True
76
The best method of leak checking is when the refrigeration system is open to the atmosphere.
standing with dry nitrogen pressure of 150 psig in the system
77
When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form
acid
78
Noncondensable gases ____
are undesirable in a refrigeration system
79
To pull a vacuum means to
lower the pressure in a refrigeration system below atmosphere
80
A compound gauge
a indicates pressures above 14.696 psia
b. indicates pressures in inches Hg below atmospheric pressure
c. is one of two gauges on a typical gauge manifold
d. All of the above
d. All of the above
81
A micron gauge is wed to measure
absolute pressures below I mm Hg
82
what pressure range does the technician valve off the vacuum pump when evacuating to a deep vacuum?
500 to 300 microns
83
Which of the following represents the lowest vacuum?
1000 microns
84
A multiple evacuation means that
you pull a vacuum on a refrigeration system more than once, allowing refrigerant or nitrogen into the system between each procedure
85
Moisture in a liquid state must be ________ before it can be removed with a vacuum pump
Vaporized
86
To insure accurate testing, the best material to use for connecting lines to the vacuum pump and gauge set is
copper tube
87
The maximum recommended pressure for leak testing is 150 psig on the low-pressure side of he system
a. True
b. False
True
88
Air entering a refrigerant system can eventually lead to compressor failure
a. True
b. False
False
89
Clearance tolerances are such that the ordinary clean refrigerant oil can be used satisfactorily in a vacuum pump
a True
b. False
True
90
The oil in a vacuum pump should be changed after each time it is used
a. True
b. False
True
91
While under a deep vacuum, any liquid water under the ail in the motor-compressor assembly can be removed by operating the compressor motor for several seconds without any adverse effect on the system
a. True
b. False
False
92
After repairing a system that has had an electrical motor failure (compressor burnout), it in good field practice to reuse the recovered refrigerant in that system.
a. True
b. False
False
93
When using a "standing pressure test for leak-checking, air should never be used since an explosive mixture can be created
true or false
True
94
Sludge is produced when moisture, acid, and oil are present in the system
a True b false
True
95
Only two substances should be in the refrigeration system for proper operation. They are water and oil
a True
B false
True
96
When all else fails, read the manual.
a. True
b. False
True
