# 3rd 6 Flashcards Preview

## 3rd 6 > 3rd 6 > Flashcards

Flashcards in 3rd 6 Deck (209)
1
Q

In a pneumatic system what provides the force that performs work?

A

compressed Air

2
Q

How much work is done by a piston that exerts a force of 15lbs through a distance of 10in?

A

150 in-lbs

3
Q

Heating a gas in a solid rigid container will ____ the ____ of the gas.

A

increase; pressure

4
Q

Two cylinders having different diameters are connected by an air line. A force is applied to the smaller piston. The larger piston exerts a force on a load and moves it. The force on the load is ____ the force applied to the small piston, and the distance load moves is ____ the distance the small piston moves.

A

greater than; less than

5
Q

When air flowing in a pipe reaches a section where the diameter is reduced, the speed of the air ____ and its pressure ____.

A

increases; decreases

6
Q

A reciprocating compressor is one kind of ____ compressor

A

positive- displacement

7
Q

In a typical reciprocating compressor, the intake valves are forced open by:

A

atmospheric pressure

8
Q

The purpose of the intercooler between the two stages of a two stage compressor is to reduce the ____

A

power needed to run

9
Q

The purpose of lubricating oil in a compressor is to reduce friction between the moving parts and:

A

improve the cooling of compressor

10
Q

A

Run without delivering air

11
Q

Single-stage sliding- vane compressors can produce pressures up to

A

50 psi

12
Q

Rotary screw compressors run at speeds ranging from ____ to ____ rpm

A

3,000 ; 12,000

13
Q

Impeller compressors deliver air at ____ volume and ____ pressure

A

high; low

14
Q

Compared to other compressors, centrifugal compressors

A

more power

15
Q

Most effective way to reduce output of a centrifugal compressor is ____, but may not work if the reduction is too ____

A

speed variation; large

16
Q

Water often collects in pneumatic systems because when air is compressed its ____ decreases

A

moisture capacity

17
Q

Most common way to remove water vapor from the air leaving a compressor is to:

A

cool the air

18
Q

Water cooled after coolers are typically used with ____ capacity compressors that run ____ hours a day

A

large; 10 or more

19
Q

A desiccant removes water from air by ____ it.

A

absorbing

20
Q

The main purpose of a receiver in a pneumatic system

A

maintain pressure during peak demand

21
Q

The operation of an internal separator depends on

A

rapid change in the direction of air flow

22
Q

Of the particles listed, the smallest are the ____ particles

A

aerosol

23
Q

A filter can stop 100% of the particles down to a specific min size. Known as the filter’s ____ rating

A

absolute

24
Q

An advantage of wetted filters over dry

A

can be cleaned many times

25
Q

A fine mist lubricator should be used in a system if air flow is ____ and/or distance to the equipment is ____

A

intermittent; long

26
Q

Laminar air flow in a system is made turbulent by

A

constrictions in pipe

27
Q

Greater pressure losses occur if air is at ____ pressure, because of greater ____

A

low; friction

28
Q

When used as a compressor discharge line, a pipe run should slope ____ in the direction of flow by 1in for every ____ ft

A

downward; 10

29
Q

When should you use pipe joint compound in connecting NPT- threaded pipe?

A

Either
-if joint can’t be tightly fitted
Or
- never

30
Q

If an air hose is not completely depressurized when you disconnect it, the danger is a sudden

A

blowing of dust or chips

31
Q

A four way valve has four

A

connecting ports

32
Q

The ____ valve is a good throttling device and is suitable for high pressure service. It causes ____ pressure losses in the line

A

needle; high

33
Q

The spool in a valve controls the flow of air by ____ from one piston to another. In a high pressure system, the spool is ____ to move

A

sliding; easy

34
Q

An advantage of 4-way valves over 2-way and 3-way is that they

A

simplify controls

35
Q

A valve has 5 connecting ports, 2 of which are exhaust ports. The valves is a

A

4-way

36
Q

The cracking pressure of a simple poppet type relief valve is determined by the

A

37
Q

A diaphragm type relief valve responds very quickly to a pressure change because of its

A

larger pressure sensitive area

38
Q

The only purpose of a pressure relief valve is to

A

prevent damage

39
Q

An increase in pressure on a secondary side of a pressure regulating valve ____ the valve

A

slightly closes

40
Q

The best way to guard against excessive pressure on the secondary side of a pressure regulator is

A

use a regulator with a built in relief valve

41
Q

The thrust that can be applied when a rod of a single rod, double-acting cylinder is moving out of a cylinder is ____ the thrust that can be applied when the rod is moving in

A

greater than

42
Q

An internal spring is sometimes used to return the piston in a ____-acting ____ rod pneumatic cylinder

A

single; single

43
Q

The main purpose of an exhaust flow control metering valve on a pneumatic cylinder is to

A

limit return stroke speed

44
Q

A cylinder that must be free to pivot requires a(n) ____ mounting

A

trunnion or clevis

45
Q

You can determine whether a control valve can deliver air enough for a cylinder by calculating the ____ required by the valve

A

capacity coefficient

46
Q

The highest torque a pneumatic motor can exert on a load is its ____ torque

A

stalling

47
Q

The HP of a pneumatic motor varies with the ____ and the ____ of the motor shaft

A

speed; torque

48
Q

The highest power output of a pneumatic motor occurs when its speed is

A

medium

49
Q

An axial-piston pneumatic motor transmits force from the piston to the output shaft by means of:

A

cam plate and gears

50
Q

Air pressure of 100psi can create hydraulic pressure of 1000psi if the air piston drives a ____ hydraulic piston

A

smaller diameter

51
Q

The designation 52Y indicates the device is a ____

A

circuit breaker, anti-pump auxiliary

52
Q

The accepted industry standard for showing relay contacts on circuit diagrams is to show the contacts assuming the relay is

A

de-energized

53
Q

Protective relay zones of protection are overlapped to:

A

avoid leaving unprotected areas

54
Q

A well designed protective relay system should provide 3 basic operational characteristics

A

all above

55
Q

The method of symmetrical components consists of reducing any unbalanced 3 phase system of vectors in 3 ____ systems

A

balanced

56
Q

In high current arcs in excess of 100 amps, the voltage across the arc is nearly constant at an average of around ____ volts per foot

A

400

57
Q

Open circuits on power occur more frequently than short circuits

T or F

A

False

58
Q

The current flowing out at the polarity marked terminal on the secondary side is substantially in phase with the current flowing in at the polarity marked terminal on the primary side

T or F

A

True

59
Q

The ground and neutral point on a 3 phase system are on the same point

T or F

A

False

60
Q

Circuit diagrams show ____ of the currents and voltages. [Eliminate 1]

A

magnitude

61
Q

Plasma is defined as the state of matter in which electrons are removed from atoms or molecules, creating electronically conducting gas

T or F

A

True

62
Q

The plasma performs what function when breaking a circuit?

A

flow between two open circuits

63
Q

Why must air in the breaker’s high air pressure system be very dry?

A

because it is the insulating medium between contacts

64
Q

What is the purpose of SF6 gas in air blast circuit breakers?

A

insulate the support column current

65
Q

The purpose of the blast valve is to blow the arc from the stationary to the arcing probe. It also cools and lengthens the arc so it will extinguish at the next zero current

T or F

A

True

66
Q

Which element is used as a time delay?

A

disk

67
Q

Relays reduce the number of alternate links to avoid equipment damage or limit damage to a single unit

T or F

A

True

68
Q

The links in a power system chain are: generator, power transformers, switchgear, transmission lines, distribution circuits and the utilization apparatus

T or F

A

True

69
Q

What is the most vulnerable portion of the power system chain

A

transmission lines

70
Q

Operating characteristic curves is a graph depicting the relationship of quantities that will cause the relay to operate

T or F

A

True

71
Q

What is the advantage of the induction cap

A

instantaneous operating with ability to monitor several electrical quantities

72
Q

What are the 4 basic types of electromagnetic relay operating elements

A

All above

73
Q

A device when energized by suitable currents, voltages, or both, responds to magnitudes and relationships of those values to indicate or isolate an abnormal condition. This best describes protective relays

T or F

A

True

74
Q

The difference between primary and backup relaying is that the primary is the SECONDARY defense and isolates a greater portion of the chain

T or F

A

False

75
Q

Speed of an actuator may be regulated with a

A

flow control valve

76
Q

When the flow control valve controls the amount of oil going in the actuator, the application is

A

meter-in

77
Q

In applications where the load might tend to “run away”, the flow control application should be

A

meter-out

78
Q

When the flow control is teed off supply line from the pump and determines the actuator speed by metering a portion of the pump delivery to tank, the application is

A

bleed-off

79
Q

The light spring in a bypass flow control valve holds the pressure compensator normally

A

closed

80
Q

The light speed in a restrictor type flow control holds the pressure compensator normally

A

open

81
Q

Flow through a pressure compensated flow control valve is subject to change with variations in oil ____

A

temperature

82
Q

Deceleration valves are usually used in a meter-out configuration

T or F

A

True

83
Q

The use of proportional valves requires the equipment contain ____ controls

A

electronic

84
Q

This graphical symbol depicts what valve?

[Photo pending]

A

meter-in restrictor type valve

85
Q

Pumps are generally rated by their maximum operating pressure capability and their output in ___ at a given drive speed

A

GPM

86
Q

Pump ____ is expressed in cubic inches per revolution

A

displacement

87
Q

Most pumps have a ____ displacement which cannot be changed easily

A

fixed

88
Q

Volumetric efficiency is equal to actual output divided by ____ output

A

theoretical

89
Q

High pressures at gear pump outlet imposes a(n) ____ load on the gears and bearings supporting them

A

unbalanced

90
Q

Most fixed displacement vane pumps utilize the ____ cartridge design

A

balanced

91
Q

Intra-vane pumps have holes drilled through the rotor segments to ____ pressure

A

equalize

92
Q

The pistons in a(n) ____ piston pump are parallel to each other and to the axis of the cylinder block

A

axial

93
Q

In a(n) ____ piston pump, the cylinder block and drive shaft are on the same centerline and the pistons retract parallel to the drive shaft

A

inline

94
Q

In a(n) ____ piston pump the cylinder block turns with the drive shaft, at an offset angle

A

bent axial

95
Q

A device used to store fluid under pressure is called a(n) ____

A

accumulator

96
Q

Regardless of the percentage of fluid in a weight loaded accumulator, the pressure remains ____

A

constant

97
Q

What type of gas is preferred for gas charged accumulators?

A

nitrogen

97
Q

Two principal types of pressure gauges are the Shrader and ____

A

Bourden

98
Q

Vacuum gauges are calibrated in inches of ____

A

mercury

99
Q

The gas precharge pressure in an accumulator should never be less than ____ the working pressure

A

1/4th

100
Q

The device used to protect a pressure gauge from surges is called a ____

A

snubber

102
Q

Accumulators may be installed in a system to absorb ____

A

shock

103
Q

The device used to boost pressure is called ____

A

intensifier

104
Q

Converts a pressure signal into an electrical signal:

A

pressure switch

105
Q

The most distinguishing feature of a pipe thread is the ____

A

shape

106
Q

Which metal is least affected by corrosion?

A

stainless steel

107
Q

____ strainers are commonly used where frequent cleaning is necessary

A

duplex

108
Q

Female end pipe fitting used for joining 2 lengths of pipe:

A

coupling

108
Q

Pipe supports are used to:

A

All above

109
Q

Pipe less than 12” in diameter is usually designated by its ____ diameter

A

inside

111
Q

For low pressures and cold services, ____ gaskets are generally used

A

rubber

112
Q

The pipe fitting used to join lengths of pipe to permit easy opening of a line:

A

union

112
Q

All pipe systems should be installed in accordance with the ____

A

ASCPP

113
Q

Warm up or ____ lines reduce wear and make large valves easier to open

A

pressure equalizing

114
Q

Pipe is coated on the outside with galvanizing, paint, insulation, or some other material to prevent:

A

All above

115
Q

____ strainers are used to automatically strain raw water to remove silt and debris

A

self- cleaning

117
Q

A ____ line is a line used to control the concentration of impurities in a pressure vessel

A

blow down

118
Q

Plastic pipe is not normally used to transfer ____

A

oil

119
Q

To differentiate between pipes carrying different substances, pipe systems are often ____

A

color coded

120
Q

Pressure reducing valves are always drained ____

A

externally

121
Q

If the vent connection of a relief valve is opened to tank the pump is said to be ____

A

122
Q

If operations take place in a certain order they are done in ____

A

sequence

123
Q

A sequence valve should contain a ____

A

check valve

124
Q

A back pressure valve is normally ____

A

open

124
Q

If flow from secondary to primary is required, the unloading valve control pressure should be ____ above the spring setting

A

150 psi

125
Q

When used to support a load, the valve functions as a ____

A

counterbalance valve

127
Q

Pressure in the outlet part of an internally drained sequence valve adds to the ___ setting

A

spring

128
Q

Pressure reducing valves with internal check valves permit ____ free flow

A

reverse

129
Q

When the unloading valve is ___ operated, the spring force and pressure in the primary part are independent of each other

A

remotely

129
Q

A brake valve is used to prevent:

A

Both A and C

130
Q

A brake valve is used in the ____ line of a hydraulic motor

A

exhaust

132
Q

When a load is being accelerated, pressure is maximum at the motor ____

A

inlet

133
Q

A back pressure valve can also be used as a ____ valve

A

134
Q

A relief valve is normally ___

A

closed

135
Q

The point at which a relief valve first opens is called its ____ pressure

A

cracking

136
Q

A relief valve limits the ____ pressure in a hydraulic system

A

max

137
Q

The difference in pressure between the points where a relief valve first opens and passes full pump delivery is sometimes called ____

A

override

138
Q

When the chamber above the balanced piston at a relief valve is opened to tank, it is said to be ____

A

vented

138
Q

The best hydraulic formula:

A

Y = f/2

139
Q

When a pressure reducing valve is vented, its outlet pressure is at its ____

A

minimum pressure

140
Q

Penstock velocities may range from:

A

6 to 20ft per sec

141
Q

A partially clogged trash rack will:

A

cause a decrease in effective head

143
Q

The most advantageous form of cross-section to use from a hydraulic point of view would be that which provide the:

A

smallest wetted perimeter

144
Q

Wood-stave pipe is not used for:

A

145
Q

In hydroelectric developments the head and flow may be subject to continuous ____

A

fluctuations

145
Q

The pumped storage type of development implies a capability of ___

A

All 3

146
Q

Negative water hammer pressure is created by

A

a sudden increase in demand for water

147
Q

Intake design has a large effect on ____

A

All 3

148
Q

Which would not cause water level in the riser to fall?

A

150
Q

The efficient type of high-line conduit is that type which

A

has the greatest effect on the available head

150
Q

Steel pipe is probably used more extensively than any other type because of the degree it offers in satisfying service criteria….

A

In all above areas

151
Q

An open conduit system implies

A

the presence of a free surface

153
Q

The advantage of using a pressure tunnel in a power conduit

A

permits full use of available head

154
Q

The simplest means of eliminating positive water hammer pressure is:

A

any above

155
Q

Transformers permit the transfer of electricity between two circuits which are:

A

completely insulated from each other

156
Q

In a transformer the winding which receives the energy inductively is called the:

A

secondary winding

157
Q

A power transformer transfers electrical power from one circuit at a certain frequency and voltage, to a second circuit at:

A

a DIFFERENT voltage and SAME frequency

158
Q

Transformers are classified as static AC machines

T or F

A

True

159
Q

A transformer developed 120V in its secondary winding when a 2,400 source was connected across the primary winding. Assuming a primary current of .25 Amps, the secondary current is:

A

5 Amps

160
Q

When the number of turns or voltage on the secondary winding of a transformer is greater than that of the primary, it is known as a:

A

step-up transformer

161
Q

Transformers only having ONE winding are called:

A

autotransformers

162
Q

The secondary of a potential transformer should never be

A

short circuited to remove the device it operates from service

163
Q

What is the induced secondary voltage of a transformer having a primary winding of 3,000 turns and a secondary winding of 300 turns, when connected to a 2,400V source?

A

240V

164
Q

In a core-type transformer:

A

A section of the primary and secondary windings are wound around each leg of the core

165
Q

Current transformers are instrument transformers use to:

A

step current down

166
Q

Hysteresis can be explained as

A

friction of the molecules due to alternating current

167
Q

When a transformer’s windings are connected in WYE:

A

the line current will be the same as the phase current

168
Q

A series street lighting system requires what type of transformer?

A

a constant current transformer

169
Q

The rating of a transformer is usually given in:

A

all above

170
Q

Bushings are used in transformers to:

A

serve as entrances into the transformer for the main leads

171
Q

The conservator system is used on transformers to:

A

preserve the dielectric strength of the transformer oil

172
Q

The secondary of a current transformer should never be

A

opened to remove the device it operates from service

173
Q

In an energized transformer iron losses are present even if there is no load on the secondary.

Tor F

A

True

174
Q

In a transformer a ____ must always exist between the primary and the secondary fields to maintain the required current to supply the transformer losses and secondary load.

A

balanced condition

175
Q

Whenever a circuit which is carrying current is opened:

A

the current tends to continue to flow across the contacts as they separate

176
Q

The initials TPDT would normally be used to identify a type of:

A

knife switch

177
Q

The type of switch usually used to interrupt field current to generators and synchronous machines is a:

A

field switch

178
Q

Disconnect switches are commonly used on 440 Volts or higher circuits to:

A

isolate the electrical equipment or circuits not in service

179
Q

Of the following statements concerning mercury control switches, the one which is most nearly not correct is:

A

they are generally used only when the circuit voltage is 120 volts or less

180
Q

The main difference between a circuit breaker and other kinds of electrical switches is that circuit breakers:

A

open automatically when the current exceeds a predetermined limit

181
Q

Which of the below statements does not correctly describe a means or method for quenching an arc?

A

reducing the reluctance across the contacts

182
Q

A blowout coil would most likely be found in:

A

an air-magnetic circuit breaker

183
Q

of the following statements, the one which most nearly describes what is meant by trip-free operation is:

A

the precedence which takes place over any closing operation

184
Q

A trip-free operation takes place if:

A

the circuit breaker is closed while the protective relay is energized

185
Q

Circuit breakers are generally classified by:

A

all the above

186
Q

Speed is a desirable quality during the tripping operation of a circuit breaker to:

A

all the above

187
Q

The energy needed to rapidly open the contacts of most circuit breaker designs is usually provided by:

A

springs and gravity

188
Q

Of the following statements concerning OCBs the one which is not correct is:

A

The AC arc is ALWAYS extinguished during the first zero current

189
Q

The closing time of an OCB becomes more important when it is considered from the standpoint of:

A

synchronizing generators

190
Q

A fast realistic circuit breaker opening operation (arc-out) time would be:

A

three to four cycles

191
Q

The high dielectric strength of gases, such as SF6, under static conditions is maintained by:

A

pressurizing

192
Q

A 3 phase 138kV circuit breaker can interrupt 12,000 amps. What is its interrupting capacity in MVA?

A

1656 MVA

193
Q

A 34.5kV circuit breaker has a rated interrupting capacity of 25,000 amps. What will be its approximate interrupting capacity when used on a 20kV circuit?

A

25,000 amps

194
Q

A 4.58kV circuit breaker has an interrupting rating of 30,000 amps. What is its interrupting capacity when used at 5.1 kV?

A

28,235 amps

195
Q

In fig 28, which is not true?

A

the pallet switches indicate that the OCB is in a closed position

196
Q

Concerning fuses, which is not true?

A

they are all non-repetitive in design

197
Q

Fuses serve the same purpose as:

A

circuit breakers

198
Q

A ____ is a device which functions when the circuit admittance, impedance, or reactance increases or decreases beyond predetermined limits

A

distance relay

199
Q

The reason for not replacing blown fuses with copper is:

A

the desired circuit protection against overload may be lost

200
Q

____ is adjusted separately for the degree of overcurrent at which it operates and also for the amount of time delay.

A

induction disk time-relay

201
Q

the term zones of protection applies most nearly to the isolation of faulted equipment:

A

throughout the entire power system

202
Q

The induction-disk time overcurrent is:

A

both A and B

203
Q

A device by which contacts in one circuit are operated by a change in conditions in the same or another circuit is:

A

a relay

204
Q

Protective relays must be able to:

A

all the above

205
Q

Relays may be classified in a number of ways except:

A

the manner in which it is connected in a circuit

206
Q

Differential current relays are designed to:

A

protect against internal faults

207
Q

When CTs are used with protective relays the direction of current flow in the transformer windings (polarity marks) :

A

must be carefully observed for relay types which depend on the interaction of 2 currents for their action.

208
Q

____ are used to protect polyphase rotating equipment from single or unbalanced phase operations:

A

phase balance relays

209
Q

The protective device for motor branch circuit should:

A

not be of the instantaneous type