H.R.C. fuse, as compared to a rewirable fuse, has

Question

Examoogle · Accepted Answer

all of the above

Explanation: An H.R.C. (High Rupturing Capacity) fuse is a specialized protective device designed to safely interrupt extremely high short-circuit currents. It overcomes the limitations of traditional rewirable fuses by utilizing a sealed construction, which eliminates deterioration and ensures precise, consistent operation under fault conditions.

Working Principle: The H.R.C. fuse operates on the principle of thermal melting where a silver-fused element is embedded in an arc-quenching medium like quartz sand. Upon a fault, the element vaporizes; the resulting metal vapor reacts with the sand to form a high-resistance fulgurite, which effectively quenches the arc and limits the fault current ($I_{cut-off}$) to a very low value within milliseconds.

Key Formulas: $I_{cut-off} \ll I_{prospective}$ — Indicates the current-limiting property where the cut-off current is much lower than the prospective fault current.; $t = \frac{K \cdot A^2}{I^2}$ — Represents the melting time relationship, where $t$ is time, $A$ is cross-section, and $K$ is a constant related to material resistivity.

Key Points: H.R.C. fuses provide consistent protection due to their sealed container preventing oxidation.; The inverse time-current characteristic ensures fast operation at high fault levels.; They are effectively used in industrial distribution systems for short-circuit protection.; The arc-quenching medium (quartz sand) is crucial for extinguishing high-energy arcs.

Advantages: Excellent current-limiting performance; Precise operation with no ageing effect; High rupturing capacity for large short-circuit currents

Disadvantages: Cannot be reused; must be replaced after operation; Higher initial cost compared to rewirable fuses

Applications: Industrial power distribution boards; Transformer secondary protection; Motor circuit starters

Additional Info: The term 'H.R.C.' stands for High Rupturing Capacity, referring to the ability to clear faults of 33kA to 100kA or more.. Option A is correct because the fuse element is hermetically sealed.. Option B is correct because the current-limiting action occurs before the current reaches its first peak.. Option C is correct as it is the defining characteristic of the device.

Answer: D is correct — H.R.C. fuses are engineered to provide high rupturing capacity, fast operation speeds, and immunity to ageing, making them superior to rewirable fuses in industrial applications.

Exam Tip: When analyzing protective devices, always remember that 'current-limiting' capability is the primary factor that makes H.R.C. fuses superior to MCBs and rewirable fuses for clearing heavy faults.

Related Questions

Discussion (0)