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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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Fuse rating is expressed in
Voltage
Current
VAR
KVA
Current
Quick Summary: A fuse is a protective device whose primary function is to break the electrical circuit when the current exceeds a specific predefined value. Therefore, its rating is strictly determined by the maximum safe continuous current it can carry before the element melts, which is expressed in Amperes (A).
A fuse is a protective device whose primary function is to break the electrical circuit when the current exceeds a specific predefined value. Therefore, its rating is strictly determined by the maximum safe continuous current it can carry before the element melts, which is expressed in Amperes (A).
H=I2Rt — represents the heat energy generated in the fuse element
Irated=RtH — represents the basis for determining current rating
The fuse element is designed with a specific material and cross-sectional area such that the I2R heat generated by the passage of current follows the formula H=I2Rt. Once the current crosses the rated value, the heat generated exceeds the heat dissipation capacity of the fuse, causing the element to melt and open the circuit, thereby protecting the downstream equipment.
Fuses are classified based on current rating, breaking capacity, and time-current characteristics.
The fuse rating represents the maximum current that can flow through the fuse continuously without degradation.
A fuse is a thermal-based protective device.
Cost-effective protection
High current limiting capability
Cannot be reused after operation
Replacement requires manual intervention
Domestic wiring circuits
Industrial motor protection
Voltage rating of a fuse specifies the maximum voltage at which the fuse can safely clear a fault without arcing.
Option A (Voltage) relates to the insulation capability, not the load-carrying capacity.
Option C (VAR) and D (KVA) refer to power ratings which are not used to size simple fuse elements.
B is correct — Fuse rating is primarily expressed in Amperes, representing the maximum current the device can sustain continuously.
Always remember that protective devices like Fuses are rated by Current (Amperes), while Transformers are rated by Power (KVA/MVA).