Electrical System Components Flashcards

What is the purpose of a surge protective device (SPD) installed at the service entrance?

Answer: Divert transient overvoltages to ground

An SPD diverts transient overvoltages (such as from lightning or switching surges) to the grounding system to protect connected equipment.

Which conductor color is used for the high leg (wild leg) of a 240/120V delta system?

Answer: Orange

NEC 110.15 requires the high leg of a 4-wire delta system to be identified with orange color to warn of the higher voltage to ground.

What is the function of a neutral-to-ground bond in the main service panel?

Answer: Establish a reference voltage and provide a fault return path

The neutral-to-ground bond at the service point establishes ground as the voltage reference and provides a fault current return path back to the source.

Which device automatically disconnects power when arc-fault conditions are detected?

Answer: AFCI breaker

An AFCI (Arc-Fault Circuit Interrupter) breaker detects arcing signatures and disconnects the circuit to prevent electrical fires.

What is the standard voltage drop allowance recommended by the NEC for a branch circuit?

Answer: 3%

The NEC recommends (as a fine print note) that branch circuit voltage drop not exceed 3% for good performance.

Which type of bushing is required when rigid metal conduit enters a cabinet or enclosure without a threaded hub?

Answer: Insulating bushing or insulated fitting

An insulating bushing or insulated fitting is required to protect conductors from abrasion where conduit enters enclosures without a threaded hub.

A dual-element time-delay fuse is preferred over a standard fuse for motor circuits because it:

Answer: Withstands motor starting inrush without nuisance blowing

Dual-element fuses have a time-delay element that withstands the high inrush current during motor starting without nuisance operation.