Reading time ( words)
Cars were a lot less safe for automotive consumers back in the 1950s and ‘60s. Besides including seats without seatbelts and non-collapsing steering wheel columns, the cars of my childhood era sported solid steel dashboards with plenty of glaring, distractive chrome. Every dashboard boasted a cigarette lighter and ashtray, allowing the driver to completely fill the passenger area with second-hand smoke while their kids bounced around unrestrained on the rear bench seat mounted directly above the gas tank.
Design emphasis was more on futuristic styling and less on safety. The 1957 Chevy Bel-Air and the 1961 Cadillac Biarritz may have been stylish and powerful, but they didn’t have anything like today’s crumple zones. In fact, most cars of that era were made of heavy steel and old-fashioned glass that could shatter during a collision and harm the car’s occupants. It wasn’t until later in the ‘60s and ‘70s that car manufacturers were required to use improved laminated windshields that could withstand greater impacts without breaking loose and posing a mortal threat during a collision.
Automotive safety issues like the ones I’ve described were highlighted in a book entitled Unsafe at Any Speed: The Designed-In Dangers of the American Automobile, published in 1965 by a 32-year-old lawyer named Ralph Nader. In his book, Nader took aim at the auto makers of Detroit. He accused them of ignoring issues of automotive design safety for reasons of cost and failing to incorporate what we might term today as DFS—design for safety. He inculpated designers for not considering the effects of a car’s interior on the human body during a crash, which was morbidly referred to as “the second collision.”
Nader’s book is significant because he stood up to criticize “Big Auto” for cost-cutting on design safety. He used compelling data to make consumers tangibly aware of how they were being blamed by Detroit for the injury and harm caused by vehicular accidents. In effect, Nader identified the automotive consumer as a project stakeholder. He included automotive passengers and even crosswalk pedestrians as stakeholders for which consideration for avoiding the potential to cause injury or harm must be incorporated into every automobile design.
What Has Changed in 50 Years?
The safety issues described in Nader’s book were mechanical by nature. I’ve searched for anything written about electrical safety concerns, but I’ve found no safety issues regarding high voltage electricity. Systems were low voltage based on 6V or 12V systems. Cars didn’t even use electricity until around the 1920s when electric starter motors were added to crank the motor over automatically to start the car. The earliest automotive electrical safety scare I can remember occurred when I saw sparks fly off the jumper cables when helping my dad jump start our old 1964 Volkswagen Karmann Ghia. I still cringe in fear while attaching jumper cables to this day.
Over five decades later, many of the mechanical safety issues of the past have been addressed through the work of the National Highway Traffic Safety Administration (NHTSA). However, as we continue into the dawn of the advanced electric vehicle (EV) era, there continues to be new safety challenges to understand and to monitor as we experience the exponential growth in the development and utilization of high voltage systems into the cars we will drive.
Defining High Voltage
Many countries use different voltage and frequency standards for power distribution networks. The U.S. uses 120V/60Hz while much of Europe and South Africa use a 230V/50Hz standard. Jamaica uses 100V/50Hz or 60Hz standard. Safety must be considered when bringing a high voltage potential onto a printed circuit design and breaking it down to lower operating voltages. But what potential is considered high voltage in the first place? There are many variables to consider when determining what is high voltage. The minimum voltage experienced by a static (electrostatic discharge) shock is 3,000V but this is harmless due to its very low current. Some commissions define high voltage as >1,000V AC RMS and 1,500V for DC voltage.
As designers of printed circuit-based electronics know, there are design guidelines for voltage ranges and testing which must be included in design and manufacturing workflows in order for a circuit board assembly to be certified as safe for intended applications, including electric vehicles. IPC-2221 and IEC/UL 60950 are go-to specifications for those regarding creepage and clearance requirements for conductors to eliminate the occurrence of electrical arcing, which can be a potential cause of fire or electrical shock.
This installment of Target Condition is not intended to teach design for high voltage. I wrote it to implore our readers to learn about the risks and precautions which must be taken in the design and handling of high voltage electronics from the in-depth subject matter provided by the knowledgeable authors contributing to this issue. My message is one of awareness, to watch out for our fellow stakeholders and to inspire a healthy regard for any potential safety risks when utilizing high voltage and high current. The target condition for the design of high voltage PCB layouts may be summarized as: “Mitigating potential to cause injury or harm.”
Let us read. Let us learn. And let us incorporate knowledge about electrical safety for the benefit of our project stakeholders.
A Low-Voltage Childhood
As a kid, I went on to experience electricity in the ways kids do. As a Cub Scout, I made a lemon battery using galvanized nails, pennies, and some copper wire to power a flashlight bulb. I connected a 1.5V dry cell battery to the glow plug of my Cox .049 airplane motor and understood how it served to ignite the fuel in the motor to get it to run. I survived a schoolyard challenge to touch both terminals of a Ray-O-Vac 9V battery to my tongue. I connected transformer terminal wires to my electric train set and enjoyed watching my friend’s older brothers work on their electric slot cars they would race with incredible acceleration and speed at the local hobby tracks.
I had a mostly “low-voltage” childhood experience and I thankfully stopped short of electrocuting my young self through experimentation with wall sockets and screwdrivers as did the kid over on the next block. Fifty years later (except for connecting jumper cables), I’ve mostly lost my fear of sparks and have been working in the low voltage realm designing printed circuit boards with some occasional high voltage requirements thrown in.
A Shocking EV Car Experience
Last May, I began driving a 75-mile round trip to work for a new employer. With the price of gas skyrocketing, I began to seriously consider getting into the electric vehicle market, so I started shopping. The first challenge was availability. It seemed there were no EVs available in the inland Pacific Northwest. But no sooner did I find a dealer with a new electric vehicle than I was informed that it was being recalled due to the failure of its high-voltage power system. Evidently some of these EV owners had their garages burned down by that particular model.
There go those pesky safety issues again. I’d read many positive EV reviews and evaluations. Except for that particular EV, it appears that the EV market has done very well in improvements, making the electric cars mechanically safe, thanks in part to all of the visibility brought about by Nader and the NHTSA.
But now our next-generation electric vehicles are utilizing technology which has the potential to stretch safety concerns into unfamiliar areas. In the high-voltage electric automobile era, will our modern EV automakers go the way of the “Big Auto” of the past and sacrifice safety in the name of greater driving range, power, torque, autonomous driving capability, and the bottom line?
I hope not, because I’ve finally found the perfect EV for my commuting need. I’ve stepped up my personal operational voltage rating by purchasing a well-known 2018 EV model which was recently brought into the dealer as a returned lease car. It had only 19,000 miles with no recall or safety issues. It has proven to be an outstanding “learner” EV. For a minimal investment, I have driven it almost 4,000 miles without a problem.
I’ve “filled up” at commercially available, high-voltage EV charging stations in less than a half an hour. The charging station (cable) that came with the car, however, seemed to be woefully slow at charging the car. Plugged into a normal 120V/20A wall socket using an adaptor, I couldn’t recharge the car’s battery to the level it was the day before, even after leaving it plugged in for 12 hours. It was easy to recognize the benefit of utilizing higher voltage. I scheduled a date with our local electrician who ran a 240V/50A service out to the garage to connect to the charging station. This install allowed the car to be fully charged within a relatively short four hours after returning home each day from my 75-mile commute.
I now consider myself a regular stakeholder—an end-user—of the high-voltage EV industry. Considering all the high-voltage electronics that surround me in this vehicle, as a PCB designer, I find myself more observant of potential high-voltage safety risks than ever. Both as a consumer and a PCB designer, I’d like to publicly thank all high-voltage electronics project team stakeholders, including my local electrician Josh, for serving the EV industry.
I’m having a wonderful experience so far. Thank you for following and evolving the industry’s standards and guidelines. You have helped me safely transition to silent, zero-emission commuting costing only 6.8 cents per kilowatt hour.
To all our PCB stakeholders, see you next month or sooner!
This column originally appeared in the January 2022 issue of Design007 Magazine.