Circuit Protection Devices

In Circuit Protection Devices , you'll learn ...

• Why circuit protection devices are needed
• Fuse types, ratings, and selection criteria
• Circuit breaker types, ratings and selection criteria
• Selective tripping and why it is used

Overview

Credit: 2 PDH

Length: 41 pages

Too much current flowing through an electric circuit can damage the circuit and create a safety hazard. How much current is "too much current?" That depends on the circuit and its components. For some circuits, 1 ampere would be too much current, while for other circuits 1 ampere would be perfectly acceptable. Circuit protection devices protect electrical equipment by rapidly disconnecting power to components in the event of abnormal overload conditions resulting from excessive voltages, ground faults, and accidental shorting of a circuit.

Two types of circuit protection devices are common; fuses and circuit breakers both operate by opening and interrupting current to the circuit. A fuse or circuit breaker is designed to create an open circuit if too much current flows through it. You can think of it as a switch that automatically turns itself off if the current through it exceeds a certain level. When a fuse is "blown" by having too much current pass through it, the fuse is ruined and must be replaced. On the other hand, when a circuit breaker is "tripped" by excessive current, the circuit breaker can be reset and used again, instead of being discarded. The choice of which to use depends on the specific application, circuit type, electrical specifications, space available, environmental constraints, and customer preference.

A proper circuit protection strategy reduces long-term maintenance needs and other costs, and minimizes system downtime. This 2-hour course provides an overview of circuit protection devices.