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Sattler > Generators, motors, thermocouples and tachometers > Flashcards

Generators, motors, thermocouples and tachometers Flashcards

1
Q

Current of each leg of delta and Y-Connected generator is divided by?

A

1.73

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2
Q

Equation for finding out (F) Hertz

A

F = # of poles x RPM / 120

Fuck = nopR 120

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3
Q

What is the horsepower equation?

A

[2π(rpm)(torque)]/33,000

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4
Q

What is an electric brake?

A

A device operated by electromagnetic means which functions to bring a load to rest mechanically and hold it at rest.

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5
Q

What are the 2 types of rotors in generators?

A

Salient pole and cylindrical types.

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6
Q

For synchronous speeds of 1,800 RPM’s and lower you will use a ______________ rotor.

A

Salient pole

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7
Q

For synchronous speeds of 3,600 RPM’s and higher you will use a _____________ rotor.

A

Cylindrical

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8
Q

What piece of equipment is an instrument capable of generating, transmitting and indicating information that can be converted into a measurable of rotational speed?

A

Tachometer

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9
Q

Where do you compare proper operation of rotating equipment RPM?

A

Name data plate

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10
Q

Equation for finding RPM?

A

120 x F / # of poles

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11
Q

What are the 3 types of hand held tachometers?

A

Centrifugal, Photo Electric and Chronometric

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12
Q

A sensor that converts a measurable pressure into an electrical output signal that is proportionate to the input pressure is?

A

Pressure transducer

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13
Q

What are the 2 types of pressure transducers?

A

DC 2 wire system and AC 4 wire system.

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14
Q

What is max length cable for 0-5VDC pressure transducer system?

A

100 feet because of interference

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15
Q

What’s a common problem in pressure transducers?

A

Moisture inside of it

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16
Q

Kings Nitronic pressure transducer uses what gas?

A

Nitrogen

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17
Q

When replacing transducer make sure what?

A

Right wire size…

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18
Q

What is an RTD?

A

Resistance Temperature Detector

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19
Q

What are the 2 types of elements of RTD’s?

A

Nickel 40-400 degrees

Platinum 40-1,100 degrees

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20
Q

2 wire RTD colors are?

A

1 red and 1 white

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21
Q

3 wire RTD wire color is?

A

2 white and 1 red

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22
Q

What does positive temperature coefficient mean?

A

As temperature raises so does resistance

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23
Q

What are the 3 types of configuration of RTD’s?

A

Thermowell, Bare Bulb, Embedded

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24
Q

What is a thermocouple?

A

A device used to measure temperature.

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25
Q

K Type thermocouple is made up of?

A

Chromel (Yellow +) and Alumel (Red -)

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26
Q

J Type thermocouple is made up of?

A

Iron (white +) and constantan (red -)

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27
Q

Air gap through the distance and thousands of an inch between the _________ and __________?

A

Stator and rotor

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28
Q

Air gap should be within _____% tolerance.

A

10%

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29
Q

Air gaps are measured with a ________________________?

A

Feeler Gauge

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30
Q

2 ways for installing bearings?

A

Arbor press and heat method

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31
Q

Preferred seating method is using what grit sand paper?

A

80

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32
Q

The mag pickup is used to detect the speed of the _________?

A

Prime mover

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33
Q

Forcing to much grease into a bearing may cause _______ and eventually _________ to the bearing.

A

Overheating and destruction

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34
Q

Chattering of a contactor may indicate what?

A

Rusty or pitted surface of the contacts

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35
Q

What are the 2 procedures for checking the temperature of windings?

A

Thermometer method or resistance method

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36
Q

Portable power tools must be checked?

A

Quarterly

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37
Q

What must never be used to clean contacts of a contacter?

A

Emory cloth

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38
Q

The gap reading between mag pickup and the gear should be ______ inches

A

.01-.04

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39
Q

What component accomplishes speed in phase matching up generators?

A

Synchronizer

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40
Q

One of the more common malfunctions of a synchronizer is no _________ control.

A

Governor

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41
Q

What component senses the output voltage of the generator compares a sample of that voltage with a reference voltage and supplies the field power necessary to maintain the predetermined ratio between the generator voltage and the reference voltage?

A

Voltage regulator

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42
Q

One of the most common problems of a voltage regulator is?

A

Over voltage

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43
Q

Why do you check windings temperatures on motors and generators?

A

To compare insulation resistance

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44
Q

The purpose of the polarization index test is to determine the condition of the?

A

Generator windings

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45
Q

If soft foot hasn’t improved in ____ corrective attempts, a bent foot condition may exist.

A

2

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46
Q

As the ambient air temperature changes, the cold junction will begin to produce its own electrical potential. This would cause an erroneous reading of the actual thermocouple. What is this called?

A

Cold junction compensation

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47
Q

A thermocouple is a key sensing component of a _______?

A

Pyrometer

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48
Q

What type of tachometer is used if the rotating shaft is not readily accessible?

A

Resonant

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49
Q

The prime mover stabilized using various types of?

A

Feedback

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50
Q

Brush holders are reaction type with 2 brushes inclined __________ ___________ at 35 degrees?

A

Against rotation

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51
Q

What is a generator heated with?

A

Stand-by exciter

52
Q

What is the function of the reverse power relay?

A

Circuit protection for the prime mover

53
Q

What type of adjustments can be made to the reverse power relay?

A

Time delay and a set point adjustment

54
Q

An electrical motor that turns a generator to supply the closely regulated type III electrical power is known as an _______________?

A

Motor generator set

55
Q

Motor insulation temperature of 10°C or higher than the manufactures recommendation will shorten the insulation life by how much?

A

Half

56
Q

What is the distance of the mag pick up from the gear?

A

.25 and 1.02mm
Or
.010 and .40”

57
Q

What item will shut the prime mover down if the magnetic pickup signal fails?

A

Speed sensing failsafe

58
Q

What is the purpose of the magnetic pick-up?

A

Used to detect the speed of the prime mover.

59
Q

The 2301a electric control requires a minimum output of how many volts from the magnetic speed pickup at the lowest control setting?

A

1.5 volts

60
Q

What item generates an AC voltage whose frequency is proportional to the prime mover types and sizes?

A

2301 control, mag pick-up, current transformers.

61
Q

Soft foot is corrected by adding what?

A

Shims

62
Q

A condition that exists when the bottom of all 4 feet of a machine are not on the same place is called what?

A

Soft foot

63
Q

Why are brushes on motors adjusted?

A

To keep brush pressure constant.

64
Q

The woodward PGA-EG governor/actuator is designed specifically for marine applications requiring ______ control and ______ backup?

A

Electronic control and Mechanical backup

65
Q

What interface is used to make adjustments to the 723plus electronic governor control unit?

A

Watch Windows

66
Q

In a governor control system, the prime mover is stabilized by using various types of ______?

A

Feedback

67
Q

On modern commutating equipment, under what condition is some sparking under the brushes considered normal?

A

At high speeds

68
Q

Rated frequency of a motor or a generator can be found?

A

On the machines nameplate data

69
Q

What information is found on a hand held tachometer?

A

Calibration date and due date

70
Q

Thermocouples will produce what type of electrical output?

A

Millivolts

71
Q

Motor insulation temperature of 10 degrees C or higher than the manufacturer’s recommendation will shorten the insulation by ?

A

1/2

72
Q

Why do you check winding temperatures on motors and generators?

A

To compare insulation resistance measurements

73
Q

What chart must be used to correct insulation resistance measurements to 25°C

A

Insulation resistance-temperature nomograph

74
Q

What are the 2 methods for checking winding temperatures?

A

Thermometer method and resistance method

75
Q

The purpose of the polarization index test is to determine the condition of the _______?

A

Generator windings

76
Q

What is the purpose of checking the air gaps of motors and generators?

A

To monitor the equipment for abnormal conditions

77
Q

Checking the phase balance and rotation on motors and generators prevents ______ for occurring?

A

Decreased efficiency

78
Q

What indication would you see if a motor or generator was out of phase?

A

Decrease if the efficiency

79
Q

What are the 2 acceptable methods for installing bearings?

A

Arbor press and the heat method

80
Q

Brush holders distance from the commutator should be not more that _____ and no less than _____ of an inch.

A

1/8 and 1/16

81
Q

What method do you use to fix staggered brushes and what does this prevent?

A

Wrap 80 grit sand paper around collector and manually rotate it 5-6 times.

This prevents curving of the commutator.

82
Q

Why must 2 machines be aligned?

A

To prevent premature machinery failure

83
Q

What tolerances are checked when aligning the pump and the motor shaft?

A

In service and caution tolerance

84
Q

If a soft foot condition has not improved after 2 correction attempts, a ________ exists?

A

Worn foot

85
Q

What is the preferred method for checking pump shaft alignment?

A

Indicator reverse method

86
Q

The difference between rated speed and synchronous speed is called?

A

Slip

87
Q

The percentage of a motor can be overloaded for a short period of time is called?

A

Service factor

88
Q

Which type of overload device is heat sensitive and connected in series with a motor load circuit?

A

Thermal overload

89
Q

What are the 2 types of contacts on motor controllers called?

A

Main and Auxiliary

90
Q

What % over the load should fuses be in transformer and inductive load circuits?

A

125%

91
Q

what motor component sustains the weight of the rotor and keeps it precisely centered within the stator?

A

End bells

92
Q

What indicates the period of time in which the motor will run fully loaded at rated speed without overheating and exceeding a predetermined temperature rise?

A

Duty

93
Q

What is the reference for the resistance test record card?

A

NAVSHIP Form 531

94
Q

How long do megger cards stay onboard?

A

The life of the equipment being tested, if equipment is removed off the ship, the cards go with it.

95
Q

What are 3 types of overload relays designed to interrupt the motor circuit and prevent damage to the windings and insulation?

A
  1. Thermal
  2. Magnetic
  3. Electronic overloads
96
Q

Which component of an electric motor causes current to lead voltage, thus increasing torque during start up?

A

Capacitor

97
Q

On NAVSHIP form 531, each vertical line represents _____ days?

A

5

98
Q

Magnetic pickup voltage _________ as the air gap is _________?

A

Decreases

Increases

99
Q

Motors and generators used on propulsion plants are usually insulted with class ___ insulting material?

A

B

100
Q

Generators and propulsion equipment should be cleaned?

A

Monthly

101
Q

When 2 or more DC generators are connected what device disconnects a generator from the line if the generator starts drawing from the line?

A

A reverse CURRENT relay

102
Q

How do you clean the contacts of a contactor?

A

You don’t. They are self cleaning

103
Q

When a motor or generator is submersed in salt water, what should you do to fix it?

A

Flushed out with fresh water and let it dry. Never let the equipment dry before flushing it with fresh water.

104
Q

What motor is the most used aboard ships?

A

Polyphase induction AC motor

105
Q

What rule should you use to determine the direction of the induced EMF coil?

A

The left handed rule

106
Q

What is the purpose of slip rings?

A

To conduct the currents induced in the armature to an external load.

107
Q

What component causes a generator to produce DC voltage rather then AC voltage at its output terminals?

A

The commutator

108
Q

What causes sparking between the brushes and the commutator?

A

Improper commutation

109
Q

Magnetic induction occurs when there is motion between what 2 elements?

A

Conductor and the magnetic field

110
Q

The part of the alternator in which the output voltage is generated is?

A

Armature

111
Q

What does the term single phase mean?

A

One voltage or one output

112
Q

What determines the phase relationship between the voltages in a 2 phase AC generator?

A

Placement of the armature coils

113
Q

In 3 phase motors what is the phase relationship between individual output voltages?

A

Each phase is displace 120 degrees from the other 2

114
Q

What are the 2 ways of connecting the outputs from a 3 phase alternator?

A

Wye and Delta

115
Q

What transformers and connectors are used to convert 450/3 phase to 115 volt single phase?

A

3 single phase, delta-delta, step down transformers.

116
Q

What are the 3 types of AC motors?

A

Series, synchronous, induction

117
Q

Series motors generally operate what type of equipment?

A

Small appliances

118
Q

Why are series motors sometimes called universal motors?

A

The can operate at either AC or DC voltages

119
Q

Angular displacement between field poles in a 2 phase motor are how many degrees?

A

90

120
Q

Major difference between 2 and 3 phase motors?

A

Number and location of the field poles

121
Q

What requirements is the synchronous motor specifically designed to meet?

A

Constant speed required by some loads

122
Q

Why are induction motors used most often?

A

The are simple and inexpensive to make

123
Q

What determines the amount of slip in a motor?

A

The load

124
Q

When seating brushes 100%, brushes are?

A

Glossy with no distinct lines

125
Q

Brush pressure should be _____ lb/in is the manufacture tech pub isn’t available?

A

2 - 2-1/2 lb/in

126
Q

A power factor meter connected to measure the phase relation between the generator and bus bar voltages, the moving element is free to rotate continuously.

This defines?

A

Synchroscope

127
Q

What is the voltage and frequency variation on motors installed on ships?

A

10% +/- voltage

5% +/- frequency

Sattler (28 decks)

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