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Motor Controls > Midterm Review > Flashcards

Midterm Review Flashcards

1
Q

What type of metal remains in a liquid state at room temp

A

Mercury

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2
Q

What two factors determine the amount of voltage produced by a thermocouple

A

Type of material, temperature difference of the junctions

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3
Q

What is a thermopile

A

Thermocouples connected in series

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4
Q

What does RTD stand for

A

Resistance temperature device

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5
Q

What type of wire is used to make an RTD

A

Platinum

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6
Q

What type of material is a thermistor made of

A

Semi-conductive

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7
Q

If temperature increases in a silicon diode will voltage drop increase or decrease

A

Decrease

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8
Q

What type of chemical is used to cause a pressure change in a bellows type thermostat

A

Refrigerants

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9
Q

What material was used to make the first hall generator

A

Gold

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10
Q

What two factors determine the POLARITY of the output voltage produced my the hall generator

A

1.) direction of current flow
2.) polarity of the magnetic field

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11
Q

What two factors determine the amount of VOLTAGE produced by the hall generator

A

1.) Amount of current
2.) strength of current

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12
Q

A ferrous metal disc used to shunt a magnetic field

A

A reluctor

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13
Q

In a hall generator is the voltage produce A/C or D/C

A

D/C

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14
Q

What type of electric circuit is used to increase the sensitivity of a proximity detector

A

Tank circuit

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15
Q

What type of proximity detector uses an oscillator that operates at radio frequencies?

A

All-metal detector

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16
Q

Two types of proximity detectors used to detect objects not made of metal

A

Capacitive proximity, ultrasonic proximity

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17
Q

What is the maximum range that most proximity detectors can be used to sense an object

A

25mm (1”)

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18
Q

Three major categories of photo detectors

A

Photovoltaic, photoemmisive, photo-conductive

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19
Q

Which category of photodetectors does the solar cell belong

A

Photovoltaic

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20
Q

Which category of photodetectors does the cad cell belong

A

Photo conductive

21
Q

The term cad cell is a name for what device

A

Cadmium sulfide cell

22
Q

What is the function of the transmitter in a photodetectorunit

A

The light source

23
Q

What is the advantage of a photodetector that uses a reflector

A

Need electrical connection at only one pice of equipment

24
Q

How much voltage does a silicon solar cell produce

A

0.5 volts

25
Q

What determines the amount of current a solar cell produces

A

The surface area of the cell

26
Q

What is the operating voltage of most magnetic control systems

A

120v

27
Q

How many primary windings do control transformers have

A

2

28
Q

How are the primary windings connected to operate on a 240v system

A

Parallel

29
Q

How are the primary windings connected on the control transformer to operate at 240v

A

Parallel

30
Q

How are the control transformer windings connected to operate at 480v

A

Series

31
Q

Why are two primary leads crossed on a control transformer

A

To make connection to the primary winding easier

32
Q

Two basic classifications of timers

A

On delay, off delay

33
Q

How are pneumatic timers adjusted

A

Adjusting the needle valve

34
Q

Two methods used by electronic timers to obtain their time base

A

RC time constant
Quartz clock

35
Q

What is meant by the statement that solenoid valves are digital devices

A

They are completely on or completely off

36
Q

What type of valve is generally used to supply air pressure to a DOUBLE acting cylinder

A

Four-way

37
Q

What two sections are generally used to operate motor operated valves

A

Local and remote

38
Q

What type of switch is used to ensure a motor operated valve is tightly seated

A

A torque switch

39
Q

3 methods of braking a motor

A

Mechanical, dynamic, plugging

40
Q

What type of braking is used on cranes

A

Mechanical

41
Q

The Amount of counter torque produced by a dc generator is proportional to what?

A

Armature current

42
Q

How is braking time controlled when using dynamic braking

A

Adjusting the resistance value

43
Q

How is plugging accomplished

A

Momentarily disconnect power. Momentarily reverse the motor

44
Q

What device is used to stop a motor when plugging is used

A

0 speed switch

45
Q

What two electrical components are connected in series with a motor to limit starting current

A

Resistors and reactors

46
Q

Does resistive or reactive current rise at an exponential rate

A

Reactive

47
Q

What three percentages of line voltage do auto transformers permit to the motor during starting

A

50,65,80

48
Q

Closed transition

A

Ensures motor is never disconnected from line voltage until the motor is at full voltage

Motor Controls (1 decks)

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