Electrical Systems Quiz

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Questions and Answers

What is the primary purpose of alternating current generators?

To provide power for elevators

To control signal systems

To convert mechanical energy into electrical energy

To furnish electrical energy for power and lighting (correct)

Which of the following best describes the function of a direct current generator?

To convert electrical energy into mechanical energy

To change voltage levels in electrical circuits

To generate power for lighting applications

To supply electric energy for specific systems like elevators and signals (correct)

What is the role of an electric motor?

To generate electrical energy from rotational forces

To transform electrical energy into mechanical energy (correct)

To convert electrical energy into thermal energy

To regulate voltage levels in transformers

Which of the following is NOT a type of transformer?

Voltage regulator Signup and view all the answers

What distinguishes an oil-insulated transformer from a dry type transformer?

The insulation medium used Signup and view all the answers

What is a primary purpose of conduits in electrical installations?

To provide a system ground path. Signup and view all the answers

Which type of steel conduit is referred to as RSC?

Heavy-wall steel conduit Signup and view all the answers

What is the approximate thickness of Intermediate Metal Conduit (IMC)?

0.071 mm Signup and view all the answers

What type of conduit is not threaded and uses set screws for fittings?

Electric Metal Tubing Signup and view all the answers

Which conduit type is recommended for installation in direct contact with the earth?

Hot-dip galvanized steel conduit Signup and view all the answers

What advantage do Intermediate Metal Conduits (IMC) have over Rigid Steel Conduits (RSC)?

They yield a larger inside diameter for easier wire pulling. Signup and view all the answers

What is the standard length of steel conduits mentioned?

3 m Signup and view all the answers

Which type of conduit is not recommended for embedding in concrete?

Electric Metal Tubing Signup and view all the answers

What is the primary function of an Automatic Transfer Switch (ATS)?

To supply emergency power automatically on normal power failure. Signup and view all the answers

Which of the following materials are common for making wall plates?

Phenolic compound and Bakelite. Signup and view all the answers

What type of devices are primarily used to prevent overheating in electrical circuits?

Over-current Circuit Protective Devices. Signup and view all the answers

Which of the following is NOT a type of wall plate?

Triple-pole. Signup and view all the answers

What devices are specifically mentioned as common forms of Over-current Circuit Protective Devices?

Fuses and circuit breakers. Signup and view all the answers

What is the role of a faceplate in electrical installations?

To protect outlets or switches. Signup and view all the answers

In a wall plate specification, what does 'gang' refer to?

The number of devices it can cover. Signup and view all the answers

Which component is essential for automatically cutting off a circuit during overloads or short circuits?

Circuit breaker. Signup and view all the answers

What is the primary function of switchboards?

To provide power protection and switching for circuits Signup and view all the answers

Which type of switchboard has all live parts mounted on the exposed face?

Live Front Signup and view all the answers

What is a characteristic of Dead Front switchboards?

All live parts are behind the panel Signup and view all the answers

What does a unit substation primarily do?

Supply power from a primary voltage line to a large facility Signup and view all the answers

What is a disadvantage of knob and tube wiring?

It is considered obsolete and not very safe Signup and view all the answers

Which wiring method offers significant fireproof properties among wiring systems?

Rigid Metal Conduit Wiring Signup and view all the answers

What is a characteristic of Rigid Metal Conduit Wiring?

It resists damage from nails and cement Signup and view all the answers

What provides access to conduits in Rigid Metal Conduit Wiring systems?

Sheet metal boxes with knockout holes Signup and view all the answers

What is the primary function of a fuse in an electrical circuit?

To break the circuit during dangerous overcurrent situations Signup and view all the answers

What type of fuse is designed specifically for use in circuits not exceeding 125 volts?

Plug Fuse Signup and view all the answers

Which type of fuse has a current rating from 70 to 600 amperes?

Cartridge Fuse with knife blade contacts Signup and view all the answers

What is a characteristic of the open link fuse?

It is typically installed in a cabinet for safety Signup and view all the answers

What is a defining feature of renewable fuses?

They allow for the insertion of a new fuse link Signup and view all the answers

Which voltage rating is associated with cartridge type fuses that have ferrule contacts?

250 to 600 volts Signup and view all the answers

In general, a wire should be protected by a fuse that is rated for what relative to the wire's amperage?

An equal or lower rating Signup and view all the answers

Which type of fuse is classified as nonrenewable?

Plug fuse in a ceramic shell Signup and view all the answers

Study Notes

Automatic Transfer Switch

A double throw switch, generally a 3-pole, used for emergency or standby service.
When normal power fails, it supplies power automatically from the designated emergency service.

Wall Plates or Faceplates

Coverings for switches and wall outlets, made of metal or phenolic compounds.
Commonly single-gang, two-gang, or three-gang.

Over-Current Circuit Protective Devices

Protect insulation, wiring, switches, and other equipment from overheating or burning.
Prevent damage due to overloads, faults, or short circuits by automatically cutting off the circuit.
The two most common devices are fuses and circuit breakers.

Alternating Current Generators or Alternators

Used to produce electrical energy in the form of alternating current.
Power and lighting energy is typically supplied by generators.

Direct Current Generators

Supplies electrical energy used in systems like elevators, inter-communicating phone systems, and clock controls.

Motors

Converts electrical energy into mechanical energy.

Transformers

Used to convert electrical voltage from lower to higher (step-up transformer) or higher to lower (step-down transformer).
Two types include oil-insulated and dry type.

Purpose of Conduits

Protect enclosed conductors from mechanical and chemical damage.
Provide grounded enclosure to protect people from electrical shock hazards.
Provide a system ground path.
Prevent fire hazards due to overheating or short circuits.
Support conductors.

Rigid Steel Conduits (RSC)

A heavy-wall steel conduit with an approximate thickness of 0.117 mm.

Intermediate Metal Conduit (IMC)

Wall thickness of approximately 0.071 mm.

Electric Metal Tubing (EMT)

A thin-wall steel conduit.

Steel Conduit Installations

RSC and IMC use the same fittings (condulets) and are threaded alike.
EMT uses set screws and pressure fittings due to being unthreaded.
Standard length of steel conduit is 3m or 10ft.
Hot-dip galvanized steel conduit is recommended for direct contact with the earth.
Joints should be coated with asphaltum.

Fuses

Devices used to protect circuits from overcurrents.
Contain an alloy wire link with a low melting point that melts and opens the circuit when dangerous current flows.

Types of Fuses

Plug Fuse: Porcelain-capped fuse for circuits up to 125 volts with a rating of 10-30 amperes.
Cartridge Fuse: Insulating fiber tube enclosed fuse:
- Ferrule Contacts: 250-600 volts, 5-60 ampere rating.
- Knife Blade Contacts: 250-600 volts, 70-600 ampere rating.
- Bolted Knife Blade Contacts: 500 volts, 300-3000 ampere rating.
Open Link Fuse: Consists of easily melted wire or strip. Only used for sizes under 600 amps and must be placed in a cabinet.

Fuse Classification

One-time Use: Fuses that cannot be reused after blowing.
Renewable: Fuses that can have new fuse links inserted to replace the blown one.

General Rule for Fuse Usage

The fuse should be rated below or equal to the current rating of the wire it protects.

Standard Types of Fuses

Nonrenewable plug fuse
Nonrenewable knife blade fuse
Nonrenewable dual element time delay ferrule cartridge fuses

Switchboards

Assemblies of switches, fuses, and/or circuit breakers that provide switching and feeder protection for various circuits connecting to a main source.

Types of Switchboards

Live Front: Current-carrying parts are mounted on the exposed front of the panel.
Dead Front: Live parts are located behind the panel, controlled using insulated handles extending through holes in the front.

Unit Substations (Transfer Load Centers)

Assemblies that include a primary switch-fuse-breaker, step-down transformer, meters, controls, bus bars, and a secondary switchboard.
Used to supply power from a primary voltage line to large facilities.

Wiring Methods

Knob and Tube Wiring: Obsolete wiring method using single insulated conductors secured to porcelain knobs and tubes. Wires within walls are inserted into fire-resistant loom tubing.
Rigid Metal Conduit Wiring: Considered the best and most expensive wiring method due to its fireproof, moisture-proof, and mechanically strong properties. Provides protection against blows and cement contact.

Access to Conduits

Conduit installations utilize sheet metal boxes with knockout holes to access and connect wires at regular intervals.

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Description

Test your knowledge on essential electrical systems components such as automatic transfer switches, protective devices, and generators. This quiz covers critical aspects of both alternating and direct current systems, as well as safety mechanisms. Perfect for students or professionals in electrical engineering.