​​​​​​🚆 Mobility – Railway & Traction Systems

​

Mobility has been the proving ground of my innovations — from India’s first indigenous AC locomotives to validation ecosystems that set global benchmarks.

• Leadership: 30+ years shaping India’s propulsion journey — from the first 3‑phase AC locomotives to next‑gen indigenous converters.

​

• Platforms: Locomotives, EMUs, MEMUs, DEMUs, diesel systems, hotel load converters, and regenerative test labs.

​

• Global Parity to Future Leadership:

• Established India in traction power electronics and controls at par with the best global firms through my work at Medha (2011–12) and flagship next‑generation propulsion projects with 100+ inventions (2019–21).

• Building on this foundation — and the 1,000+ inventions since 2021 — I now combine advanced power electronics, control strategies, and cross‑domain integration to deliver high efficiency, reliability, and scalability.

• This platform enables any partner — company, institution, or country — to leapfrog from their current position to global leadership in propulsion and mobility systems.​​​

​

​🚆 AC Locomotive Converters – Three‑Phase Technology (Since 1994)

​

🚆 Early Modernization (1994–97, 
ABB Transportation/Adtranz, Switzerland, India)

​

Challenge – Transitioning Indian Railways to Modern AC Propulsion
Indian Railways needed to modernize from DC to three‑phase AC propulsion, with higher efficiency, reliability, and long‑term sustainability

​

​Innovation – First Three‑Phase AC Propulsion for India
As the sole Indian engineer in the Swiss core development team, I co‑developed India’s first three‑phase AC locomotive propulsion with GTO‑based traction converters.  Key contributions included:

• Authored key line‑ and motor‑side control modules.

​

• Invented harmonic rejection control.

​

• Validated with MATLAB/Simulink & real‑time simulation.

​

• Designed type test protocols, presented and convinced Indian Railways Directors, and led line‑ and motor‑side software during testing.

​

• Trained Indian Railways staff in Switzerland and India and delivered lectures to universities on Three Phase Technology.

​

• Drove indigenization of components and trained internal teams to build sustainable in‑house capability.

​

Impact – Foundation for India’s Modernization & Indigenization

• Established the foundation for India’s modernization program in propulsion technology.

​

• Enabled long‑term indigenization of AC propulsion systems.

​

• Transferred knowledge and built local expertise that sustained future projects.

​​

🌍 Global Breakthroughs (2007-2010,
ABB Switzerland, Bombardier Switzerland)

​

​Challenge – Driving Next‑Gen Propulsion & Global Engineering Efficiency

• By the mid‑2000s, railways worldwide were demanding higher‑efficiency propulsion, advanced converter platforms, and harmonized standards.  At the same time, global OEMs needed to streamline engineering operations across multiple sites while retaining quality and innovation.

​

Innovation – Converter Platforms, Standards, Outsourcing Leadership

ABB Switzerland (2002-07)

• Enabled the first IGBT traction converter order for Indian Railways, replacing legacy GTO systems with a preliminary design based Technical Offer.

​

• Contributed to the EU’s MODTRAIN standards, participated in the UIC converter review, and represented the Business Unit for next‑gen auxiliaries at CRC.

​

• Advanced my earlier invention of paralleling converters without communication (originally developed in Distributed Generation) for traction applications, enabling scalable and reliable multi‑converter operation.

​

Bombardier Transportation (2007-10)

​

• Directed global outsourcing strategy, consolidating five worldwide sites into two high‑performing Indian centres, achieving +40% efficiency.

​

• Implemented governance frameworks, KPIs, and contributed to development of automated workflow tools that became benchmarks across divisions.

​

• Developed an AI‑based Electrical System Compatibility (ESC) tool for DC locos, harmonizing performance analysis across global sites.

​

Impact – Global Standards & Efficiency

• Accelerated modernization by securing India’s first IGBT traction converter order, proving ABB’s technical leadership.

​

• Demonstrated the viability of converter paralleling without communication in traction, extending an invention from distributed generation into rail.

​

• Established outsourcing governance frameworks that became a benchmark across Bombardier, improving efficiency and transparency.

​​

​Indigenous Transition (2011–12, Medha, India)

​

Challenge – Building Indigenous IGBT Propulsion PlatformsIndia needed to reduce dependence on imports and establish indigenous IGBT propulsion systems across AC locomotives, EMUs, MEMUs, and DEMUs to ensure long‑term self‑reliance and scalability.

​

Innovation – Platform‑Based R&D & Converter Delivery

• Directed 19 projects across AC locos, EMUs, DEMUs, diesel systems.

​

• Built platform‑based R&D system for scalability and cost reduction.

​

• Designed 3 MW diesel converters, hotel load converters, auxiliary converters, and Arno replacement systems.

​​

• Established 25 kV OHE lab for realistic testing.

• Developed an advanced line harmonics calculation tool with a full mutual‑inductance transformer model (e.g., WAP7 topology), while most suppliers relied on simplified models without mutual inductance

​

• Invented new busbars, topologies, and control schemes

​

• Developed an improvement scheme for a new gate drive and gate drive power supply, enhancing efficiency and reducing space requirements

​

• Introduced a novel IGBT protection concept: measuring IGBT current directly with a new current sensor integrated into the gate drive, enabling much faster fault detection and protection response.

​

Impact – Explosive Growth & Indigenous Capability

• Significant impact of my work in Medha turnover scaling from ₹2B → ₹30B.

​

• Delivered India’s first indigenous IGBT propulsion platforms, breaking dependence on imports.

​

• Trained engineers, developed suppliers, and built a sustainable indigenous ecosystem for propulsion technology.

​

• Set a new benchmark in analytical modelling by introducing mutual‑inductance‑based harmonics analysis, surpassing the simplified approaches used by most global suppliers.

​

• Laid the groundwork for advanced gate drive and protection concepts later refined and expanded at SK Consultants, ensuring continuity and evolution of innovation.

​

​🚩 Flagship Project: Next‑Generation Propulsion System (2019–21, Board Member, SK Consutants)

​​

Challenge– Building a Complete Indigenous Propulsion Ecosystem

• Indian Railways, seeking to expand its indigenous supplier base, required a comprehensive propulsion electronics platform for AC locomotives comprising traction, auxiliary, (hotel load), battery charging converters, Vehicle Control Units (VCUs), and Driver Display Units (DDUs).

​

• The first requests came from DMW Patiala, followed by DLW Varanasi and other production units, confirming the need for a scalable, indigenous solution.

​

Innovation – Entire Technology Delivered from SK Consultants

As Board Member & Head of Propulsion Division, I delivered the entire technology stack from SK Consultants, personally designing, and directing implementation of the full system, while drawing on a select professional network to accelerate delivery.  Contributions included:

• Converter Systems → Complete design and specifications for traction, auxiliary, hotel load, and battery charging converters (including small‑scale prototypes), plus VCUs and DDUs; developed train‑level platform concepts for AC EMUs, MEMUs, and Train‑18/Vande Bharat with propulsion equipment specifications.

​​

• Control Hardware → Common platform based on TI dual‑core 28379D processors; delivered processor, power supply, Analog and Digital I/O for TC and VCU, communication and optical pulse interface, and backplane cards with Gerber files, CAD drawings, and full BoMs; DDU prototype built on Toradex SBC with Linux OS, QT GUI, GPRS, custom keyboard, and VCU simulator.

​​​

• Control Software → Directed closed‑loop control for converters (ALG), SLG and VCU (FLG) with my proprietary algorithms and architecture; guided simulation, implementation, and testing step‑by‑step.

​

• Embedded Real‑Time Simulator (RTS): One processor core running RTS, the other live control, enabling safe, accelerated validation without external HIL.

​

• High‑Power Lab Infrastructure: Designed and commissioned 1 MW supplied 5 MW back‑to‑back test system, integrating actual locomotive equipment along with small‑scale implementations.

​​

• Mechanical & Layout Innovations: Cold plate and cooling system design, layout of two single phase and 3 full three‑phase inverters, overvoltage limiting chopper, control hardware, modular compact layouts and ultra‑low inductance busbars with uniform current spread and minimal temperature variation, other busbars and cables with standard equipment.

​

• Training & Knowledge Transfer → Structured programs in hardware, software, simulation, and lab practices; personally trained engineers step‑by‑step in lab use, control software, and RTS validation.

​

​Impact – Full Propulsion Electronics Ecosystem

• Platform now under locomotive trials, demonstrating reliability and scalability.

​

• Reduced commissioning risk and time through in‑core RTS validation.

​

• Delivered a repeatable framework for future propulsion projects.

​

• Established a benchmark 5 MW regenerative lab facility for propulsion testing in India.

​

• Trained dozens of engineers into independent contributors, creating sustainable indigenous capability.

​

• Represented a step‑change in value: not just a converter, but an entire propulsion ecosystem with sophisticated lab — designed, validated, and industrialized indigenously, and supported by proven leadership and a robust management system

• Elevated SK Consultants into a national innovation ecosystem, positioning it as a trusted partner for power electroncis and control applications.

​​​​​​​​​​​​​​

⚡ ACEMU, MEMU Propulsion Platform Converters
(Medha, 2011–12)

​

Challenge – Breaking the abroad Technology Dependence

• Until 2011, Indian Railways’ AC EMU and MEMU trains relied on propulsion systems from Siemens and BHEL foreign collaboration.

​​​

• These systems were functional but not fully indigenous, keeping India dependent on external suppliers for critical know‑how, components, and upgrades.

​​​

• At Medha, there was no indigenous AC EMU/MEMU propulsion platform when I joined.  The challenge was to create one from scratch that could compete head‑to‑head with Global suppliers.​

​

Innovation – Creating the First Indigenous AC EMU/MEMU Platform

• Designed and simulated the first indigenous AC EMU/MEMU propulsion platform converters at Medha.

​

• Leveraged the Hotel Load electric power platform as the basis for the new ACEMU/MEMU traction converter, ensuring continuity in design and proven reliability.

​​

• Applied a common line‑side control platform across AC Loco, AC EMU/MEMU, and Electric Hotel Load systems to unify design and reduce complexity.

​​

• Adapted motor control algorithms from the AC Loco platform for EMU/MEMU traction, ensuring proven performance and reliability.

​

• Completed the design and simulation before my departure, established the foundation on which the later hardware was entirely built.​

​​

​Impact – Strategic and Technical Breakthrough

• Delivered a stable, reliable indigenous propulsion base for AC EMU and MEMU trains.

​​

• Proved that Medha could compete directly with leading global firms, offering a fully indigenous alternative.

​

• Reduced costs, shortened development cycles, and gave Indian Railways a domestic technology base for future upgrades.

​

• Established a shared propulsion ecosystem across Diesel and EMU/MEMU, accelerating Medha’s innovation cycle.​

​

​​​​​​​​​

​🚂 Diesel Locomotive & Hotel Load Systems
(Medha, 2011–12)

​

Challenge 1 – Breaking Dependence on Foreign Converters​

• Until 2011, Indian Railways’ diesel locomotives relied on EMD with Mitsubishi converters and Siemens systems.

​

• Medha had attempted an indigenous diesel converter before my arrival — a bold step — but the units suffered from power electronic design flaws that caused field failures (burning in service), compounded by wheel‑slip and poor control response. 

​

• These setbacks risked undermining confidence in indigenous solutions and could have kept India dependent on imports.

​

Innovation – Robust Indigenous Diesel Converter​

• Redesigned the 3 MW converter (6 × 500 kW) with advanced laminated busbars, digital gate drives, and upgraded control hardware/software.

​

• Corrected the power electronics design flaws that caused failures.​

​

• Directed simulation and implementation of vector control, robust wheel‑slip algorithms and fast control response to stabilize traction.

​

Impact​

• Delivered a reliable, high‑performance indigenous platform for diesel propulsion.

​

• Eliminated chronic failures and broke dependence on global suppliers.

​​

Challenge 2 – Hotel Load Integration with Severe Space Constraints

​

• Indian Railways required a Hotel Load underslung converter to power passenger amenities across the train (air‑conditioning, lighting, auxiliaries).

​

• The locomotives had no available space, requiring a redesign of the fuel tank to accommodate the converter.

​

• In the early trials, coaches were connected one by one, but when the second or third coach was added, the output three‑phase inverter/converter tripped consistently.

​

Innovation – India’s First Diesel Hotel Load System

​

• Directed India’s first Diesel Hotel Load system (2 × 500 kVA) using advanced power electronics and optimized control strategies.

​​​

• Significantly Improved the control software of the output converter, eliminating the tripping issues observed during trials and ensuring stable supply to multiple coaches.

​​

• Introduced a three‑level DC/DC topology to replace the earlier two‑level chopper for the future converters.  This innovation reduced device stress, improved waveform quality, lowered switching losses, and enhanced overall efficiency

• Reduced the size of the main inductor from nearly 800 kg to just ~100 kg, leading to significantly reduced cost, weight, and losses.

​​​

Impact

​

• Enabled locomotives to directly supply hotel load, eliminating the need for separate diesel power cars.

​​

• Delivered a stable, reliable power supply to passenger coaches, improving passenger comfort and operational reliability.

​​

• Reduced emissions, fuel consumption, and operational costs.

​​

• Established a future‑ready platform with the three‑level topology, setting a new benchmark for Hotel Load systems in India.

​​​

Challenge 3 – Inefficient Auxiliary Power

​​

• Diesel locomotives required the main engine to remain running for several idle hours each day simply to power auxiliary generators.

​

• This led to unnecessary fuel consumption, higher emissions, and increased wear and maintenance — even when the locomotive was not moving.

​

Innovation – Static Converter for Auxiliary Power

​

• Introduced the first static converter to replace auxiliary generators, providing efficient auxiliary power without burning fuel at idle.

​

Impact

​

• Reduced fuel consumption and emissions, cutting operating costs.

​

• Improved overall efficiency and reliability of locomotive systems.

​

• Marked a step toward greener, more sustainable diesel operations within Indian Railways.
   

Challenge 4 – High‑Power Passenger Locomotive (WDP5 “Bhim”)

​

• India’s most powerful passenger diesel locomotive required a compact, high‑power converter platform.

​

Innovation – Compact High‑Density Converter

​

• Designed a compact, high‑density converter tailored for the WDP5 “Bhim.”

​

Impact

​

• Enhanced efficiency, reliability, and power density.

​

• Set a new benchmark for diesel‑electric propulsion in India.

​​​​​​​​

​🚉 DEMU Propulsion Systems – Converter Upgrade and System-Level Stabilization (Medha, 2011–2012)

​

Challenge – Stabilizing an Emerging DEMU Propulsion Platform

• Indian Railways was transitioning from diesel-mechanical and hydraulic transmissions to IGBT-based electric propulsion for DEMUs.

​

• When I joined Medha, the DEMU propulsion system was still in its infancy — with unmitigated risks, incomplete validation, and critical reliability issues.

​

• Regenerative braking existed in control logic but was not energy‑recoverable; energy was dissipated in large rooftop resistors, adding thermal and packaging complexity.​

​

• The system required converter upgrades, hardware fixes to prevent oscillations, and real‑world validation before it could be deployment‑ready.

​

Innovation – Technical Leadership and Problem Solving

• Upgraded the converter busbars, eliminated component heating issues thereby improving reliability.

​​

• Adapted motor control software from AC Loco projects, ensuring proven performance for DEMU traction.

​

• Enhanced converter performance and system integration for stable operation.

​

• Solved key issues in lab validation, field commissioning, and inter-system compatibility, enabling smoother deployment.

​

• Ensured realistic validation by testing with the original Cummins DEMU generator.​​

​

• Provided technical leadership across engineering teams, ensuring alignment with Indian Railways’ operational requirements and future scalability.

​

Impact – Enabling Reliable DEMU Modernization

• Delivered a stable, reliable DEMU propulsion platform, reducing commissioning time and improving system stability.

​

• Contributed to India’s shift away from outdated diesel-mechanical systems toward diesel-electric traction architectures.

​

• Played a key role in stabilizing and directing one of India’s first IGBT-based DEMU propulsion platforms.​

​

📈 Test Systems for Traction Converters
I have designed and developed several advanced test system concepts, some of which have been successfully built for traction applications and deployed in real‑world environments.  These systems were created to solve the critical challenge of simulating railway operating conditions within factory settings, where only three‑phase supplies are available and direct access to single‑phase railway lines is not possible.​

​

🔑 Key Innovations
⚡ Back‑to‑Back Test Systems

​

Challenge

• Testing single‑phase Active Front End (AFE) converters in factories with only three‑phase supply caused severe unbalance.

​

• In India, this was further complicated by frequent power cuts and unstable incoming supply, disrupting test continuity and delaying validation cycles.

​​

Innovation

• Back‑to‑Back Configurations for Single‑Phase AFEs: Designed multiple configurations to enable full‑power testing without relying on railway infrastructure.

​

• Two Key Breakthroughs:

  • STATCOM‑Based Load Balancing: Stabilised the supply by dynamically compensating for unbalanced currents.

  • Isolated High‑Voltage Transformer: Used an 11 kV line‑to‑line / 0–30 kV transformer with on‑load tap changer to energise the 25 kV nominal traction transformer primary winding.

​

• Flexible Supply Options: Enabled the system to be powered line‑to‑line from low‑voltage sources — including Diesel Generators — with current balancing handled by the same STATCOM, requiring no additional Capex.

​

• Asset‑Optimised Cooling: Repurposed existing railway components (e.g., traction motor blower) to cool the back‑to‑back motor set, avoiding proprietary auxiliaries and maximising asset value.

​​

Impact

• Enabled realistic traction testing in factory environments without railway infrastructure.

​

• Delivered reliable, uninterrupted testing despite grid outages.

​

• Reduced commissioning delays and ensured consistent validation cycles.

​

• Lowered cost, space requirements, and auxiliary equipment needs while optimising residual asset value.

​

🔍 Dual‑Secondary Converters on a Common DC Link

​

Challenge

• In single‑phase traction converters with dual primaries and a shared DC link, it was difficult to extract only the loss from the primary while still ensuring realistic loading

​

• Conventional setups either over‑simplified the loading conditions through inductor connections or failed to stress the converter components as they would be in real operation.

​​

Innovation

• Smart Control Modes: Configured one converter in a current control loop and the other in a DC voltage control loop with inner current loop. This allowed one converter to operate in motoring mode while the other ran in regeneration mode to automatically maintain the DC voltage at its set value — and vice versa.

​​

• Independent Reactive Control: Enabled reactive current control in both converters independently, in any direction, whether both were in DC voltage control mode or with one converter in current control mode.

​

• Line‑Side Stress Accuracy: Ensured that line‑side semiconductors were correctly loaded up to full power, while the DC link carried only the associated losses in this section.

​​​​​

Impact

• Smart Application: Demonstrated how dual‑secondary converters can be used very effectively — not by solving the underlying architectural limitation, but by applying control modes cleverly even in stationary locomotives, as well as in lab and RTS simulations.

​

• Validation Accuracy: Enabled realistic stress on line‑side semiconductors while isolating primary losses, providing a practical method for testing and analysis.

​

• Efficiency Gains: Reduced unnecessary energy draw by circulating power between two full converters via back-to-back motors.

​

• Practical Value: Offered a pragmatic, reproducible approach for both field and lab environments, strengthening validation methodologies without additional hardware.

​

🚆 Simplified Motor Simulation / Emulation

​

Challenge

• Conventional test setups required multiple physical traction motors, making them costly, space‑intensive, and energy‑inefficient.

​

• Worse, only one motor was typically connected to an inverter, while the others were tied to inductors drawing only reactive power.

​

• As a result, semiconductors were never stressed as in real operation, and the DC link and line‑side converters were loaded only with the active power of a single motor — leaving the entire system under‑tested.

​

Innovation

• Single Back‑to‑Back Motor Set: Introduced a setup using one pair of identical traction motors, with one operating in motoring and the other in generation, while the remaining motors were replaced by inductors between the respective inverters of two separate traction converters. This eliminated bulky multi‑motor arrangements and enabled simultaneous testing of motoring and regeneration.

​

• Loss Reduction: Reduced continuous losses by 200 kW+ compared to conventional multi‑motor setups.​

​

• Full Converter Stress: Ensured that all components of the converter — semiconductors, DC link, and line‑side stages — were correctly loaded under all operating conditions and across all four quadrants.

​

• Mechanical Simplification: Eliminated the need for a flywheel, reducing mechanical complexity and footprint.

​

• Advanced Test Features: Enabled emulation of wheel‑slip conditions (with lower dynamics), similar to low‑voltage motor loading.

​

• High‑Accuracy Validation: Incorporated a precision torque sensor to verify that commanded torque matched expected values, ensuring rigorous validation of control strategies.

​

• Compact & Scalable: Designed for integration with regenerative test systems, making it suitable for both R&D labs and production environments.​

​

Impact

• Cost & Space Efficiency: Removed the need for multiple physical motors and large mechanical setups.

​

• Energy Savings: Reduced continuous losses by hundreds of kilowatts, with regenerative circulation further minimising net power draw.

​

• Technical Rigor: Closed the gap between lab testing and real‑world operation by ensuring converters were stressed under realistic conditions.

​

• Faster Development Cycles: Enabled rapid prototyping and validation without waiting for full‑scale hardware.

​

• Strategic Value: Delivered a simplified yet rigorous test methodology that accelerates innovation in traction and e‑mobility propulsion systems while lowering cost and risk.

​

​

🔄 Low‑Voltage Motor Loading & Regeneration

​

Challenge

​Testing and validating electric drives at low voltage and reduced power has always been a bottleneck in R&D and production environments. Conventional approaches required:

• Full‑voltage, full‑power setups, which were costly, space‑intensive, and energy‑inefficient.

​

• Dedicated high‑power test benches, limiting flexibility and scalability.

​

• Inefficient energy use, since most of the input power was dissipated as heat rather than recovered.

​

• Limited ability to replicate real‑world loading conditions at reduced voltage levels, making early‑stage validation difficult.

​

Innovation

• Regenerative Test Concept: Developed a methodology where two identical or similar machines are coupled mechanically, with one acting as the motor under test and the other as a regenerative load.

​

• Low‑Voltage Operation: Enabled testing at reduced DC link voltages while still replicating full‑torque and dynamic loading conditions.

​

• Energy Recovery: Instead of wasting power as heat, energy is circulated between the machines and partially fed back to the grid, drastically reducing net power consumption.

​

• Compact & Scalable: Eliminated the need for bulky high‑power resistive loads, reducing cost and footprint while allowing flexible scaling across different motor ratings.

​

• Versatile Applications: Applicable to traction drives, industrial motors, and e‑mobility propulsion systems.

​

Impact

• Cost Efficiency: Reduced capital and operational costs of test systems.

​

• Energy Savings: Enabled sustainable, regenerative testing with minimal net power draw.

​

• Space Optimisation: Freed up valuable lab and factory floor space by eliminating large load banks.

​

• Validation Accuracy: Allowed realistic motor loading and regeneration scenarios even at low voltage, accelerating early‑stage development and de‑risking full‑scale deployment.

​

• Commercial Value: Created a test methodology that is both technically rigorous and economically attractive, strengthening competitiveness in drive development and validation.

​

🌟 Overall Impact & Potential

• Comprehensive Portfolio: Delivers a suite of proven and conceptual solutions for cost‑effective, flexible, and accurate testing of traction converters — without dependence on railway or EV infrastructure.

​

• Efficiency & Fidelity: Reduces equipment needs while simultaneously improving simulation accuracy and test fidelity, ensuring converters are validated under realistic operating conditions.

​

• Cross‑Domain Applicability: Scales seamlessly across railways, e‑mobility, industrial drives, and renewable energy systems, positioning the solutions as universally relevant.

​

• Loco‑Centric Validation: Enables testing of all converter types within the locomotive itself, using the same Loco Transformer as the common test backbone.

​

• Commercial & IP Value: Several solutions are patentable and commercially attractive, creating strong opportunities for licensing, partnerships, and global collaboration.

​

• Strategic Advantage: Establishes a sustainable validation ecosystem that accelerates innovation cycles, reduces cost and risk, and strengthens indigenous leadership in propulsion and power electronics.

​

Impact

• Positioned India at global parity in traction power electronics and controls.

​

• Enabled indigenous platforms that broke foreign monopolies and scaled Medha from ₹2B → ₹30B turnover.

​

• Created a repeatable propulsion ecosystem (converters + labs + validation) that any partner can adopt to leapfrog into global leadership.

​

• Established SK Consultants as a trusted national innovation hub for rail and mobility.

​​