UEENEEE003BSolve Problems in Single Path DC Circuits

Protection Devices

There are two types or fuses:◦ SERFs semi enclosed rewireable fuses◦ HRCs high rupturing capacity

RATED VALUES◦ Current rating◦ Fault current rating

Current Rating is the current value that will cause the fuse to blow.

Fault Current Rating is the maximum current value that the fuse can interrupt.

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Fuses

Fault Current

The fault current will cause the element to melt.

This heat causes the sand to melt. The sand quickly cools and forms an

insulating barrier to cut the arc.

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For common applications Circuit Breakers can be classified as:◦ magnetic◦ thermal◦ thermal magnetic

Circuit Breakers offer the best reset, after the fault has been cleared.

Circuit breakers are common in domestic, commercial and Industrial installations

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Circuit breakers

Magnetic Circuit Breakers

Short circuit◦ The fault current creates a strong magnetic field.◦ This field forces the armature to move.◦ This movement releases a spring, forcing the contacts to

open. As this process is relatively quick, Magnetic Trip Action is best

suited to SHORT CIRCUIT PROTECTION.

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