Featured Engineer

Interview with Rakesh Dhawan

Rakesh Dhawan

Rakesh Dhawan - Chief Engineer at Strategic Technology Group, LLC

How did you get into electronics/ engineering and when did you start?

I grew up in India in the 1980’s, which was when India was a country of few choices. For my education, I could either get into engineering or medicine. I was good at math and science, so I decided to get into engineering. I had to clear an entrance examination to get into the Indian Institute of Technology and I obtained a rank of 500 or so. With that rank, I could get into the electrical engineering program. If I had a higher rank, I would have perhaps got into computer science. If I had a lower rank, I would have perhaps got into chemical or civil engineering. Computer science was the most sought after discipline, followed by electrical engineering and other disciplines, but I decided to stick with electrical engineering.

What are your favorite hardware tools that you use?

My favorite hardware tool is the Tektronix Scope TDS210. That was the first scope I bought in 1998 and I still use it. It has been the perfect tool for all my power electronics as well as motor drive projects.

What are your favorite software tools that you use?

My favorite software tools are MotorSolve and PSpice. I can simulate/analyze just about any power electronic/motor drive circuits with PSpice. I love MotorSolve, as I can design any phase (3-phase/5-phase/7-phase etc) motor with this tool and I can take the results and use them to model motors in PSpice.

What is the hardest/trickiest bug you have ever fixed?

In 1995, we had released a 13kW plasma metal cutter. It was the lightest metal cutter in the industry and quite popular. However, we had a few failing in the field. We had no idea what was going on. I visited the customer sites and tried to investigate power transients, installation procedures etc. We could not find the cause for a long time. Everything worked great in the laboratory and factory floor. Then one day, my colleague pointed out that the IGBTs of the buck converters were receiving fairly narrow pulses (~1uS or so) under certain operating conditions. We all had an “A-ha!” moment. We limited the duty cycle to 2.5uS and the failures stopped. IGBTs were going into linear mode of operation and destroying themselves.

In 2003, we released a 1kW electric bike propulsion system. We had done testing for a year and results were great. It was the first motor of its kind with electronics inside and 1kW of output power. This project was so much fun. The electronics worked perfectly. It was a great marriage of electromagnetic, mechanical, thermal, motor, electrical and software engineering. As we began to ramp up production, we had unexpected MOSFET failures. All hell broke loose. I was scratching my head. We searched and searched and could not find an answer for a long time. One day as I was observing the waveforms, I saw battery current dip for a few micro-seconds, which was curious. I investigated further and discovered that under certain operating conditions, MOSFETs of a half-bridge were experiencing shoot-thru. By sheer confluence of manufacturing factors (PCB manufacturing etc.), shoot thru became quite rampant. I had to clean up gate drive routing of the low side MOSFETs ensuring that the lowside MOSFET gate drive current returned straight back to the driver IC and did not go through the power ground. It fixed the problem and we never had a MOSFET failure again.

What is on your bookshelf?

I have tons of technical books, conference proceedings, IEEE technical papers etc. However, the book I will recommend to everybody is “Surely You’re Joking Mr. Feynman!” A must-read for every budding engineer.

Do you have any tricks up your sleeve?

Yes. One trick I tell everybody in my teal is that in order to create a world-class product, you must acquire knowledge about every aspect of your design. You must understand the circuit, the operation, the datasheets, the components, the layout etc. completely. Product engineering is that girl/boy friend who will not go to bed until you have understood each and every of her/his mood swings. If you launch a product without understanding, it is surely going to come back to bite you.

What has been your favorite project?

My favorite project is the Falco eBike propulsion system. This project had the most aggressive specifications and I decided to do this in India. I had to build a team of engineers and line up suppliers from scratch. We have finally completed the development and delivered a high-power, high-torque and high-efficiency electric motor with integrated electronics and wireless control interface. We now have a great team in India and great supplier base.

Do you have any note-worthy engineering experiences?

When I got out of college (IIT-Kharagpur, 1990), I began to work at Tata Electric Companies in Mumbai, India. We were working on a 25kW motor drive system. After-hours, I used to work alone on the drive, turning it ON, taking waveforms, trying to understand its operation etc. One night, the whole motor drive blew up and we were using very expensive imported Motorola transistors. Each one easily cost $100 or more. Fortunately, I had with me a 2-year senior with me at that time. Our boss and chief engineer were extremely upset. I had to write down extensive analysis as to why it happened. It was quite an experience and my first time blowing things up.

My boss kept his confidence in me. So we had this extremely expensive missile tracking system with two motor drives. It was developed for the Army, and they came to investigate and raised their objection to an OPAMP we were using. The missile tracking system was off-site. Our chief engineer picked a new part and my boss instructed me to go take all the PCBs in the system and replaced them with new OPAMPS. He dispatched me with two female technicians. We worked all day and replaced all of the 70 OPAMPs.

The next day, I told my boss that it was completed. He proceeded to send the chief engineer to the site to get the system functional. When I told him that I had already checked the system and the system was fully functional, he almost fell from his chair. He asked how I could replace 70 ICs and turn on such a huge system alone. He was upset for a few minutes and then he was happy. He told me never to do this again.

In hindsight, it was quite a gutsy and foolish thing to do on my part. Although we had replaced all ICs meticulously, if things had gone wrong, it would have been a massive loss to the company. I should have waited for the chief engineer.

What are you currently working on?

We are currently working on further enhancing our 5-phase Falco brushless motor technology. We are hoping to convince the world to began looking at the 5-phase motor technology instead of the 3-phase. We are also planning on integrating our motor technology into wheelchairs, low-speed high-torque propulsion applications etc.

Can you tell us more about Strategic Technology Group LLC?

Strategic Technology Group is focused on providing design and consulting services in the areas of power electronics and motor drives. We have a team of 20-engineers and we deal with 8-bit to 32-bit processors for our work. We have a strong team of electromagnetic engineers, motor, mechanical, electrical, software, manufacturing, system, project and test engineers. It has been a difficult road to build this great team and I am very proud of each and every one of them.

What direction do you see your business heading in the next few years?

Our main focus is electric vehicles. We believe that electric vehicles are viable under 4-6kW. Over 6kW, they are not really viable. We plan to release several propulsion units to meet those needs.

What challenges do you foresee in our industry?

A major challenge remains the batteries. Battery technology (even Li-IOn) is 20 years behind the demands of electric vehicle industry. Fuel cell research has failed to commercialize, and we cannot provide the same energy density safely as nature does in terms of oil. Humans really suck in this field and it is the most urgent need of the society.

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