Inverters

Inverters – Verified PYQ Authority Guide

Inverters is organised as a topic-level PYQ authority page. It brings together the strongest verified question clusters, exam/year coverage and concept-level practice so students can revise the topic without jumping through unrelated notes. Every factual learning cue below is drawn from the existing verified, published and approved English PYQ corpus or from its Knowledge Graph relationships; the hub does not invent unsupported technical claims.

PYQ evidence snapshot

6 verified PYQs are currently mapped to this Topic hub. The represented years include 2026, 2025. Exam coverage currently includes Deputy Executive Engineer (Electrical), Class-2, Sports Authority of Gujarat / Assistant Engineer (Electrical), Class-2,, Assistant Engineer (Electrical), Class-2, Road and Building Department. Subject context includes Electrical Engineering. These values come from live mappings and can expand automatically when new verified PYQs are added.

Most useful verified PYQs to solve first

Start with the actual questions rather than memorising a generic note. The links below are ranked from the mapped corpus using repeat history and editorial quality, while the complete explanation stays on the individual question page.

1. Consider the performance of a 3-phase VSI. Then 1. 180° conduction provides higher fundamental output than 120° conduction. 2. 120° conduction is prone to short-circuiting the DC bus if "dead-time" is not…
   Deputy Executive Engineer (Electrical), Class-2, Sports Authority of Gujarat / Assistant Engineer (Electrical), Class-2, · 2026 · 120 versus 180 Degree Conduction
   In 180° mode three devices conduct at a time; in 120° mode only two conduct and one phase is disconnected during each step. Waveform/fundamental…
2. A single-phase full-bridge VSI is fed from a 48 V battery and delivers power to a resistive load of 10 Ω. Using square wave switching, verify 1. RMS value of fundamental output…
   Deputy Executive Engineer (Electrical), Class-2, Sports Authority of Gujarat / Assistant Engineer (Electrical), Class-2, · 2026 · Square-Wave Fundamental and Load Power
   In 180° conduction, three devices conduct at a time and the fundamental output is higher; the floating star neutral can shift relative to the…
3. In a 3-phase VSI in 120° conduction mode, 1. Each switch conducts for 120° in a cycle. 2. Only two switches conduct at any given time. 3. The phase voltage is zero…
   Deputy Executive Engineer (Electrical), Class-2, Sports Authority of Gujarat / Assistant Engineer (Electrical), Class-2, · 2026 · 120-Degree Conduction Mode
   Three-phase voltage-source inverters can be operated with 120° or 180° conduction sequences. In 120° conduction, each switch is on for 120° and only two…
4. Regarding Pulse Width Modulation (PWM) in inverters, consider the following: 1. Sinusoidal PWM reduces the lower-order harmonics but increases the switching losses. 2. The modulation index (ma) controls the amplitude of the…
   Deputy Executive Engineer (Electrical), Class-2, Sports Authority of Gujarat / Assistant Engineer (Electrical), Class-2, · 2026 · Modulation Index and Harmonics
   In the linear region, modulation index controls the fundamental output amplitude. Raising switching frequency moves dominant harmonics upward but increases switching loss. Key relation:…
5. In the case of a single−pulse width modulation with the pulse width = 2d, to eliminate the nth harmonic from the output voltage
   Assistant Engineer (Electrical), Class-2, Road and Building Department · 2025 · Selective Harmonic Elimination in Single-Pulse PWM
   For a single pulse of half-width d, the nth harmonic term contains sin(nd). To eliminate the nth harmonic, set sin(nd)=0; the non-trivial condition used…
6. In the single−pulse width modulation method, the output voltage waveform is symmetrical about ____________ in the negative half cycle.
   Assistant Engineer (Electrical), Class-2, Road and Building Department · 2025 · Single-Pulse PWM Symmetry
   For a single-pulse PWM waveform, the negative-half-cycle pulse is symmetrically located about 3π/2, just as the positive-half-cycle pulse is symmetric about π/2. This half-wave…

Formula & key-relationship bank from verified solutions

• Typical fundamental phase RMS: 180° mode ≈0.4502Vdc; 120° mode ≈0.3898Vdc. Thus 180° gives the higher fundamental component.
• Conduction duration: 120°→two switches at a time; 180°→three switches at a time.
• m_a=V_ref,peak/V_carrier,peak; linear SPWM typically m_a≤1.
• V_n ∝ sin(nd)/n For elimination: sin(nd)=0 ⇒ nd = mπ Smallest non-zero choice: nd = π
• Positive-half center = π/2 Negative-half center = 3π/2

Use these as revision triggers and open the linked PYQ before applying a formula numerically; variable definitions and assumptions belong to the exact solved question.

Core ideas repeatedly reinforced by the solved corpus

• In 180° mode three devices conduct at a time; in 120° mode only two conduct and one phase is disconnected during each step. Waveform/fundamental comparison confirms 1. The 60° same-leg off interval of 120° mode contradicts 2, and…
• In 180° conduction, three devices conduct at a time and the fundamental output is higher; the floating star neutral can shift relative to the DC midpoint. Full-bridge square-wave total RMS voltage is 48 V, so total load power=48²/10=230.4…
• Three-phase voltage-source inverters can be operated with 120° or 180° conduction sequences. In 120° conduction, each switch is on for 120° and only two devices conduct at a time, leaving one phase disconnected for intervals. Key relation: Conduction…
• In the linear region, modulation index controls the fundamental output amplitude. Raising switching frequency moves dominant harmonics upward but increases switching loss. Key relation: m_a=V_ref,peak/V_carrier,peak; linear SPWM typically m_a≤1. Exam focus: m_a controls fundamental voltage in the linear…
• For a single pulse of half-width d, the nth harmonic term contains sin(nd). To eliminate the nth harmonic, set sin(nd)=0; the non-trivial condition used in the options is nd = π.

Exam tips already validated in SRO solutions

• 120° mode: two switches ON, one phase floating. 180° mode: three switches ON.
• Track pole voltage and load-neutral voltage separately.
• m_a controls fundamental voltage in the linear region.
• Check whether d is half pulse width; the question defines full pulse width as 2d.
• Sketch one 0–2π cycle before answering PWM symmetry questions.

Common mistakes to avoid

• Assuming a balanced load forces the floating neutral to stay at zero under a non-sinusoidal switching waveform.
• Balanced load does not force the floating neutral to the DC midpoint at every switching state.
• Over-modulation is not a clean linear extension of SPWM.
• Setting 2d=π irrespective of harmonic number.
• Choosing π/2 for the negative half-cycle center.

Topic and concept coverage

Mapped topic labels include Inverters. The concept trail includes 120 versus 180 Degree Conduction, 120-Degree Conduction Mode, Modulation Index and Harmonics, Selective Harmonic Elimination in Single-Pulse PWM, Single-Pulse PWM Symmetry, Square-Wave Fundamental and Load Power. Use these labels as a revision map: move from the broad area to the narrow concept, solve a verified PYQ, inspect the detailed reasoning, and then attempt another question from the same cluster.

Knowledge Graph navigation

Continue with Power Electronics, Pulse Width Modulation, Single-Phase Full-Bridge VSI, Sinusoidal PWM, Three-Phase VSI, Electrical Engineering, 120 versus 180 Degree Conduction, 120-Degree Conduction Mode. These are canonical SRO entity links based on the Knowledge Graph and shared question mappings, not keyword-stuffed tag pages.

How to revise this authority page efficiently

1. Solve before reading: answer a mapped PYQ first.
2. Read the exact explanation: verify the correct principle, formula, distractor logic and common mistake on that question page.
3. Move one level in the graph: use the closest concept/sub-topic/topic link rather than opening unrelated content.
4. Reattempt: solve another verified PYQ from this hub and check whether the same error repeats.

Quality scope: this page is automatically maintained from SRO’s verified mapped corpus. It enriches one canonical authority URL instead of generating multiple near-duplicate pages for keyword variants. Manual authority articles are never overwritten by the automated engine.