प्राविधिक – इलेक्ट्रिकल, मेकानिकल र टेलिकम
प्राविधिक – इलेक्ट्रिकल, मेकानिकल र टेलिकम
Technical – Electrical, Mechanical & Telecom · ४,५०० प्रश्न
४,५०० प्रश्न उपलब्ध। मोड छान्नुहोस्:
इलेक्ट्रिकल र टेलिकम: प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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Once an SCR has been triggered into conduction, it can be turned off by:
सही उत्तर: ख) reducing its anode current below the holding current
After latching, the gate loses control; the SCR stops conducting only when the anode current falls below the holding current (e.g. at a natural current zero).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The three terminals of a thyristor (SCR) are:
सही उत्तर: क) anode, cathode and gate
An SCR is a four-layer PNPN device with anode, cathode and a gate terminal used to trigger it.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Distribution transformers in Nepal stepping down 11 kV for consumers normally have a secondary line voltage of about:
सही उत्तर: ग) 400 V (230 V phase to neutral)
11/0.4 kV transformers supply 400 V three-phase, four-wire, giving 230 V between phase and neutral for homes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The cooling designation ONAN on a transformer nameplate means:
सही उत्तर: क) oil natural, air natural
O = mineral oil, N = natural circulation; the first pair refers to the internal coolant and the second pair to the external coolant (air).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the approximate equivalent circuit of a transformer, the shunt (parallel) branch represents:
सही उत्तर: ख) the core (iron) loss and the magnetising current
The shunt resistance accounts for core loss and the shunt reactance for magnetising current; series elements represent winding resistance and leakage reactance.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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On-load tap changers of power transformers are usually fitted on the high-voltage winding because:
सही उत्तर: ग) it carries a smaller current, making switching easier
The HV winding carries less current, so the tap-changing contacts handle lower currents, and its many turns give finer voltage steps.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A three-phase transformer is connected star (primary) to delta (secondary) with a per-phase turns ratio of 10 : 1. With 11 kV line voltage on the primary, the secondary line voltage is about:
सही उत्तर: घ) 635 V
Primary phase voltage = 11 000/√3 ≈ 6351 V; secondary phase = 635 V, which is also the line voltage of the delta.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the transformer vector group Dyn11, the low-voltage side:
सही उत्तर: ग) is star-connected with neutral brought out and leads the high-voltage side by 30°
D = HV delta, y = LV star, n = neutral brought out, 11 = clock position 11, meaning the LV voltage leads the HV voltage by 30°.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The all-day efficiency of a distribution transformer is the ratio of:
सही उत्तर: घ) output energy (kWh) to input energy (kWh) over 24 hours
Distribution transformers are energised all day with varying load, so their performance is judged by energy efficiency over 24 hours.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Regenerative braking of a three-phase induction motor occurs when:
सही उत्तर: ख) the rotor is driven above synchronous speed, so the machine returns power to the supply
Above synchronous speed the slip is negative and the machine acts as an induction generator, e.g. when a hoist lowers a load.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
यी अभ्यास प्रश्न हुन्, आधिकारिक प्रश्न होइनन्। पाठ्यक्रम, विज्ञापन र नतिजाका लागि सम्बन्धित निकायको आधिकारिक वेबसाइट हेर्नुहोस्। उत्तरमा गल्ती भेटे प्रश्नमुनिको "टिप्पणी / गल्ती रिपोर्ट" मा लेख्नुहोस्।
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