Deck 6: Overcurrent Protection

Question 1

Define switchboard.

Answer 1

A large panel, frame, or assembly of panels in which are mounted switches, buses, overcurrent devices, and other protective equipment.

Question 2

What are the two levels of overcurrent protection that are used to protect circuits?

Answer 2

Every circuit is required to be protected by two levels of overcurrent protection: overload and short circuits or ground faults.

Question 3

During the normal operation within a building and with the motor running, there were 350 volts at the panelboard and 300 volts at the motor.Determine the percent voltage drop for this circuit.

Answer 3

Percent Voltage Drop =[(Voltage_Source - Voltage _Load )/Voltage_Source] x 100
=[(350-300)/350]x 100
= 14.3%

Question 4

The tap conductor is required to be enclosed in ____________________.

Question 5

The rules for mobile homes and manufactured homes are now the same as for other dwellings.

Question 6

Arc-fault interrupters are smaller than standard circuit breakers.

Question 7

When a fault occurs, the amount of current that flows depends on the ____________________ of the fault.

Question 8

When a graph of the current is made over time, it draws out the shape of a(n) _________________.

Question 9

There is a new requirement that all switchboards and panelboards in other than one-family and two family dwellings be marked to indicate the device or equipment where the power of a feeder originates.

Question 10

Circuit breakers are sometimes used as switches for lighting in a building.

Question 11

What is an overload?

Question 12

If two conductors with voltage between them are accidentally connected together, arcing generally will occur.

Question 13

Receptacles in dwelling bedrooms, family rooms, dining rooms, living rooms, parlors, libraries, dens, sunrooms, recreation rooms, closets, hallways, and similar areas on 15- or 20-ampere, 120-volt-rated branch-circuits are required to be protected by a(n) ___________________ of the combination type.

Question 14

High current flow during a fault will cause strong ____________________ forces that can move wires and deform electrical parts if the parts are not adequately secured and braced to withstand these forces.

Question 15

If the current wave is centered about the zero axis, then it is called a(n) ____________________ current.

Question 16

What is the purpose of overcurrent protection?

Question 17

Overcurrent devices are not permitted to be installed in the ___________________ of a dormitory.

Question 18

What causes voltage drop?

Question 19

What is rms current?

Question 20

When a circuit breaker lists two voltages, the ____________________ (higher/lower) is the voltage line to line.