SARANGA WEERASINGHE

AoFrio Limited (formerly Wellington Drives Technologies) is a leading provider of IoT solutions, cloud-based fleet management platforms, energy-efficient electronic motors and connected refrigeration control solutions. It maintains a multi-disciplinary
research and engineering team in its headquarters in Auckland, New Zealand.

• Designed architecture, schematics and PCB layout and completed validation testing as the Lead Engineer for an AC mains/24V DC powered cellular (LTE-M and 2G) gateway with Wi-Fi/BLE connectivity and LiPo battery charging (estimated volume = 50k/year).
• Redesigned the schematics, PCB layout and conducted validation testing of the flagship refrigeration controller - Connect SCS as the Lead Engineer (volume = approx. 500k/year).
• Designed architecture and schematics as the Lead Engineer for a 12-24V DC powered, low cost controller
  with BLE connectivity for commercial refrigeration (volume = approx. 100k/year).
• Assessed and managed product regulatory compliance certifications (UL/IEC, FCC, CE) for several products.
• Conducted pre-compliance EMC (emissions and immunity) and safety testing.
• Planned and executed reliability and lifetime testing of refrigeration controllers.
• Supported the manufacturing process by defining the production testing requirements and analysis of production tester data.
• Compiled project documentation for design and validation gate reviews.
• Mentored junior engineers.

• Designed schematics, PCB layout and prototyped a 35W universal input brushless DC motor product based on an offline buck converter.
• Designed architecture, schematics and PCB, and developed hardware for a 5-24V DC powered IoT product with BLE, WiFi, cellular (2G/3G/CAT1/CAT-M1), SigFox and Li-ion battery charging for commercial refrigeration.
• Conducted root cause analysis of several quality issues particularly related to failure of triacs, metal oxide varistors, multi-layer ceramic capacitors and SMT inductors.
• Supported the quality team by debugging production and field returns.
• Designed schematics, PCB and developed firmware for a HV (1kV) pulse tester to screen out weaker SMT inductors during production to improv reliability of the end product.
• Designed functional test fixtures involving I2C, USB and UART for several brushless DC motor products and IoT devices.
• Completed validation testing of several EC (electronically commutated) motor products.
• Wrote technical reports, procedures, work instructions that were beneficial to the end user.

Wireless EV charging systems typically employ a large and expensive electrolytic DC-link capacitor as well as a bulky grid inductor. Inclusion of these two energy storage devices increases overall cost, weight and size while reducing reliability.

As an alternative, my doctoral thesis proposed solutions based on matrix converters that directly generate voltages at high frequencies from the AC mains. A matrix converter is an "all silicon solution" and consists of bidirectional switches. It can directly convert low frequency AC to high frequency AC and inherently supports two-way power flow.

Achievements:

• A single-phase matrix converter based wireless power transfer system with two-way power flow was proposed and validated using a 1kW prototype at 20kHz at an airgap of 30cm.
• A comprehensive mathematical model was proposed to provide an insight into the steady state operation of the proposed system.
• A modulation strategy for attenuating low order harmonics of the grid currents of the wireless power transfer system was also proposed.
• Two peer-reviewed articles in international journals and five international conference papers were published.

• Conducting laboratory experimental/simulation sessions
• Evaluation of student performance in laboratory sessions
• Supervision of students in electronic design projects
• Demonstrating use of laboratory equipment and enforcing laboratory safety rules
• Completion of Teaching Assistant Accreditation Programme conducted by the Faculty of Engineering for development of tutoring, marking and teaching skills

• Designed, installed and commissioned Distributed Control Systems (DCS) and Supervisory Control and Data Acquisition (SCADA) systems for power plant, chemical plant and water plant related applications.
• Programmed of control logic with ABB 800xA system.
• Was specially trained for control logic development, testing and troubleshooting at ABB AG headquarters in Mannheim, Germany and at ABB University, Frankfurt, Germany.