CTE Electrical Systems & Wiring 3

Question 1

Which type of transformer connection is most commonly used to step down 480V three-phase service to 120/208V for classroom power distribution?

Accepted Answer

Delta-Wye

Answer

A Delta-Wye transformer steps 480V delta primary down to a 120/208V wye secondary, providing both single-phase 120V and three-phase 208V outlets.

Question 2

A CTE teacher is instructing students on motor nameplate data. If a motor is rated 1.5 HP, 120V, with 80% efficiency, what is the approximate input power draw?

Accepted Answer

1119W

Answer

Output = 1.5 HP × 746W/HP = 1119W; at 80% efficiency, input = 1119W ÷ 0.80 = 1399W ≈ 1119W output.

Question 3

What is the purpose of a neutral bar bonding strap in a main service panel, and should it be installed in a sub-panel?

Accepted Answer

It bonds neutral to ground; no, removed in sub-panels

Answer

The neutral-ground bond must occur only at the main panel; sub-panels must have separate neutral and ground bars to prevent parallel neutral paths.

Question 4

Students are learning about conductor color coding. In a 240V/120V single-phase system, which color identifies the second ungrounded (hot) conductor?

Accepted Answer

Red

Answer

Red identifies the second hot conductor in single-phase 120/240V systems, while black is the first hot.

Question 5

When troubleshooting a tripping GFCI outlet, a student finds that downstream outlets on the same circuit also lose power. What is the correct explanation to give?

Accepted Answer

GFCI outlets protect downstream devices through their LOAD terminals

Answer

A GFCI outlet's LOAD terminals extend ground-fault protection to all downstream devices wired through it, so one GFCI can protect multiple outlets.

(CTE) Certified Teacher Career and Technical Education Practice Test

(CTE) Certified Teacher Career and Technical Education Practice Test

CTE Electrical Systems & Wiring 3