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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A stepper motor makes 200 steps per revolution. Its step angle is:
सही उत्तर: ग) 1.8°
Step angle = 360°/200 = 1.8°.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The air-gap power of an induction motor is 20 kW and the slip is 5%. The gross mechanical power developed is:
सही उत्तर: ख) 19 kW
P_mech = (1 − s)P_ag = 0.95 × 20 = 19 kW (the remaining 1 kW is rotor copper loss).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 4-pole, 50 Hz induction motor runs with a slip of 3%. Its rotor speed is:
सही उत्तर: घ) 1455 rpm
Nₛ = 120 × 50/4 = 1500 rpm, so N = 1500(1 − 0.03) = 1455 rpm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a three-phase induction motor, the maximum (breakdown) torque occurs at a slip equal to:
सही उत्तर: ख) R₂/X₂ (rotor resistance/standstill rotor reactance)
Torque ∝ sR₂/(R₂² + s²X₂²) is maximum when sX₂ = R₂, i.e. s = R₂/X₂; the maximum value itself is independent of R₂.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Damper (amortisseur) windings on the rotor poles of a synchronous machine are mainly used to:
सही उत्तर: क) suppress hunting and help a synchronous motor start
Currents induced in the damper bars oppose oscillations of the rotor about synchronous speed, and also give induction-motor starting torque.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The V-curves of a synchronous motor show the variation of:
सही उत्तर: घ) armature current with field (excitation) current at constant load
As excitation is varied at constant load, armature current is minimum at unity power factor and rises on either side, giving a V shape.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A synchronous condenser is:
सही उत्तर: घ) an over-excited synchronous motor running without mechanical load to supply reactive power
When over-excited, a synchronous motor draws leading current, so on no load it acts like a variable capacitor for power factor and voltage control.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which of the following is NOT a necessary condition for connecting an alternator in parallel with the grid (synchronising)?
सही उत्तर: क) equal kVA ratings
Voltage magnitude, frequency, phase sequence and phase angle must match; machines of different ratings can run in parallel.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The pitch (coil-span) factor of an armature coil that is short-pitched by 30 electrical degrees is about:
सही उत्तर: ग) 0.966
k_p = cos(α/2) = cos 15° ≈ 0.966.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 50 Hz alternator has 200 turns per phase in series, a flux of 0.02 Wb per pole and a winding factor of 0.96. Its RMS emf per phase (E = 4.44fΦNk_w) is about:
सही उत्तर: ग) 852 V
E = 4.44 × 50 × 0.02 × 200 × 0.96 ≈ 852 V.
💬 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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