Special Control Circuits Flashcards

1
Q

Name the three basic types of timing devices:

A

Spring-wound interval timers
Mechanical and electronic time switches
Timing Relays

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2
Q

State an application of a Mechanical Timer:

A

Security Lighting
Landscape irrigation
Controlled Parking receptacle circuits

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3
Q

Spring-wound interval timers and time switches are reliable, inexpensive and commonly used. T or F?

A

True

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4
Q

What sort of a timing device can have their operation controlled Pnematically (air pressure) or by a fluid-filled dashpot?

A

Timing Relay

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5
Q

Electronic Timing Relays are smaller, more accurate, versatile and more cost-effective than pnematic or dashpot relays. T or F?

A

True

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6
Q

Delay on release is another name for what basic timed-contact function?

A

Time Delay on De-Energization (TDOD)

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7
Q

TDOE can allow time delays of 0.05 seconds to 300 hours. T or F?

A

True

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8
Q

What timing functions can have their relay contacts change position immediately?

A

TDOD
Interval Timing
Repeat Cycle Timing

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9
Q

Name the other timing functions apart from TDOE and TDOD:

A

Interval Timing
One-shot Timing
Repeat Cycle Timing

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10
Q

Multi-function timing relays may offer a reset terminal as a well as a _______ terminal.

A

Start.

Allows for a remote manual reset of the timing sequence or, if connected to an automatic pilot device, feedback is provided to the relay for automatic-process-condition control.

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11
Q

Why is a timing relay used in a Wye/Delta starter?

A

To allow the motor to come up to speed before it automatically changes over to Delta.

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12
Q

Describe Mechanical Friction Braking:

A

Connect a friction brake mechanism onto the motor shaft. The solenoid coil of the brake release is connected in parallel with the motor power leads and becomes energized when motor is energized.

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13
Q

To apply dynamic braking, a braking resistor is placed across the armature. T or F?

A

True

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14
Q

A motor can be stopped faster if it is connected in such a way that it acts as a generator. This is called:

A

Dynamic braking or magnetic braking

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15
Q

The amount of braking can be controlled by changing the value of the braking resistor, which in turn changes armature current. This type of braking is for:

A

Dynamic Braking for DC Motors

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16
Q

Dynamic Braking of AC Motors is called:

A

DC injection braking; dc current is applied to the stator winding of the motor

17
Q

An application that requires immediate stopping would need what method of braking?

A

Plugging : reverses the supply to two of the windings

18
Q

Anti-plugging generates a large amount of heat in the rotor due to the kinetic energy of the rotor and the coupled load. T or F?

A

False. This describes Plugging

19
Q

An Anti-Plugging switch is controlled by the rotation of the motor shaft. T or F?

A

True

20
Q

What sort of application would require an Anti-plugging braking method?

A

An application that requires the motor or load to coast to a stop before it can be reversed.

21
Q

A control circuit carries the electric signals responsible for directing the performance of a control device. T or F?

A

True

22
Q

Transformers dont have internal impedances. T or F?

A

False

23
Q

Indoor transformers have to be enclosed style. T or F?

A

False. Indoor transformers can be enclosed style or open style.

24
Q

If the higher voltage of 480 is required on the primary side of a 240/480V Transformer, the windings are connected in parallel. T or F?

A

False. To acquire 480 on primary it should be connected in series, if you wanted a 240 value, it would be connected in parallel.

25
Q

What type of fuse is recommended to protect a control transformer?

A

Time Delay