Which protective device trips to shield an SCR when a massive surge current of extremely brief duration occurs___________?
Show answer Hide answer
Answer: D. Fast acting current limiting device (FACL fuse)
Explanation
Fast-acting current limiting fuses are specifically designed to clear massive, extremely brief surge currents rapidly. They protect delicate semiconductor devices like SCRs by interrupting fault currents before thermal energy destroys silicon chips. Their ultra-fast melting characteristics limit the total clearing $I^2t$ energy delivered during severe short-circuit faults. Semiconductor devices possess very low thermal mass and cannot withstand high surge currents for more than milliseconds. Standard circuit breakers operate too slowly to protect power electronic components from catastrophic short-circuit failures. Fast-acting fuses use specialized silver element designs enclosed in arc-quenching quartz sand to clear faults instantly.
Option A circuit breakers provide primary overload and short-circuit protection but operate too slowly for SCRs. Option B snubber circuits protect against high dV/dt voltage transients rather than massive surge current faults. Option C voltage clamping devices like varistors protect against voltage overshoots rather than clearing short-circuit currents.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. How is a GTO typically triggered into the ON state___________?
Show answer Hide answer
Answer: A. Positive gate signal
Applying a positive gate voltage pulse injects carriers that forward-bias the cathode junction in GTOs. Positive gate current initiates the regenerative feedback loop needed to trigger the device into conduction. Trigger...
Q2. What harmonics are generated within a phase-controlled 3-phase ac voltage controller__________?
Show answer Hide answer
Answer: A. 2nd
Phase-controlled 3-phase AC voltage controllers typically produce characteristic odd harmonics, but due to waveform symmetry, 2nd harmonics are absent. The marked answer is likely a test-bank error.
Q3. The gate or triggering circuit of a thyristor serves as
Show answer Hide answer
Answer: A. lower power circuit.
The gate or triggering circuit of a thyristor serves as a low power circuit designed to initiate conduction. It requires only minimal electrical energy to switch the main power semiconductor from blocking to conducting s...
Q4. How does a rectifier function if its firing angle drops below zero into negative values_______________?
Show answer Hide answer
Answer: B. An inverter
When the firing angle of a converter exceeds ninety degrees into negative regions, the average DC voltage becomes negative. This negative output voltage reversal forces power to flow backward from the DC side into the AC...
Q5. How can the overall output power of a cascaded amplifier and attenuator network be calculated___________?
Show answer Hide answer
Answer: B. Actual gain of amplifier and attenuator
Overall gain in a cascaded network is determined by combining the actual gains of amplifiers and attenuators. Cascaded stages interact through their respective input and output impedances affecting total network gain. Ca...
Q6. What approach provides a reliable estimate of power demand___________?
Show answer Hide answer
Answer: C. Statistical method
The statistical method uses historical load data and probability mathematics to analyze trends in power consumption. It provides a reliable basis for estimating future electrical power demand across expanding utility dis...