Electrical Systems Quiz

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.

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.