Electrical 1.2 midterm practice #2

_____ voltage can originate from a single-phase generator.

• Single-phase

• Three-phase

• Single-phase or Three-phase

• none of these

Voltages in a three-phase circuit originate from a _____ where the voltage of each phase wire is out-of-phase with each other by 120˚.

• generator

• transformer

• motor

• all of these

Normally _____ means the contacts are closed when the coil is de-energized.

open

• closed

• powered

• none of these

• none of these

_____ transformers contain a primary and a secondary mounted on a single laminated iron core.

• Single-phase

• two-phase

• three-phase

• none of these

The _____ windings of a three-phase delta/wye-connected transformer are connected end-to-end with each other.

In a delta/delta high-leg 4-wire system, the voltage between any two primary wires is known as the “_____ line-to-line voltage,” while the voltage between any two secondary wires is referred to as the “_____ line-to-line voltage.”

• primary, primary

• secondary, secondary

• primary, secondary,

• secondary, primary

Inverse time circuit breakers have a(an) _____ trip unit that responds to short-circuit and ground-fault currents.

What is the approximate available short-circuit current on the secondary of a three-phase, 112.50 kVA, 480V to 208Y/120V transformer having an impedance rating of 2.40 percent?

• 10,500A

• 11,000A

• 12,500A

• 13,000A

The current in an arcing fault is limited by the system impedance and the impedance of the arcing fault itself. Typically, at a receptacle, fault current will be above 75A, but not likely above _____.

• 100A

• 220A

• 330A

• 450A

The resistance of a wire is affected by temperature change. This is called the _______

• temperature correction factor

• temperature coefficient

• ambient temperature factor

• none of these