It’s Important in Any Language.
By Ky Sealy
When it comes to electrical products, everyone tends to take safety for granted. When was the last time you thought about safety when using your cell phone, refrigerator, or microwave oven? Umm … never! And that’s the way it should be. You should feel comfortable interacting with electrical products without an inkling about safety. But when it comes to new products, forewarned is forearmed. You owe it to yourself to know what, if any, safety hazards you might incur when using a product.
For instance, take wireless EV charging. It’s new. It’s exciting. And because it uses the term “wireless”, it raises many questions. One common question is, “is it safe?” (Some may forget to ask if plug-in charging is safe? They should have, but we’ll leave that for another blog post). The answer is an unequivocal YES. Wireless charging IS safe. But don’t just take my word for it …
Let’s start with the magic behind wireless charging – the magnetic field
Okay, so magnetic fields aren’t magic, but they are invisible and can pass through lots of non-metallic objects without any effect whatsoever! And, I must say, it took some very clever engineering to use the magnetic fields for wireless charging of electric vehicles – so the outcome is a bit magical when compared to the mess of wires we deal with constantly today.
But how do they relate to wireless EV charging, and why should you care?
At the frequencies used for wireless EV charging, magnetic fields pass through objects, including the human body without being affected and without causing any harm whatsoever. These magnetic fields are inherently safe. In fact, the ways in which our bodies interact with magnetic and electric fields, or “electromagnetic fields” (EMF) have been studied for a long time and are well understood. Almost all electronic devices produce some level of electromagnetic fields. These products are regulated by regional authorities to ensure specified standards are met to avoid any appreciable impact to the human body whatsoever. Each country determines which local regulatory body governs standards for non-ionizing EMF, often referred to as radio frequency (RF) exposure. In the United States, the FCC sets regulations for RF exposure. In other countries, there is usually a regional governing body in charge of setting regulations. Most regional governing bodies base regulations on well-known guidelines, studies, and standards that are published. Any product that meets or exceeds the standard requirements is determined to be safe. Products that do not meet the standard criteria are not authorized to be sold. These criteria are based on solid science with a significant margin to avoid even the slightest impact. Yes, local regulations may differ from country to country; however, most follow similar guidelines.
Let’s move on to some cool foreign object detection
People ask me if wireless power for my electric vehicle will shut off if my cat climbs under the car? Or if a piece of metal lands on top of the charging pad or if my hand is placed between the ground and car charging pads? You and your cat will never experience any EMF level beyond what is known to be safe. In fact, the most that could happen, if you were to bypass all the detection mechanisms and place your hand in just the right place, would be that you might feel a tingling or “nerve stimulation” sensation that has no lasting effect. Wouldn’t it be great if we could say that about placing our hand on something hot like a stovetop?! – But I digress again. Wireless power systems for EVs have foreign object detection (FOD) systems to shut down the power transfer if you or your cat (or dog!) were to get in between – or on – the wireless power pad. Inside and outside the car, the magnetic fields are so low (lower in some cases than standing next to an EV cord charging) that there is no exposure effect whatsoever. In fact, the general public safety limits that wireless power systems are required to meet have safety factors of several orders of magnitude beyond what can potentially impact the body in any way. It is generally much safer to stand next to a vehicle wirelessly transferring thousands of watts of power than it is to hold your cell phone next to your ear or stand next to your induction cooktop while cooking.
I’m also asked if it’s safe to remain in my car while it’s charging. Yes, it is. You can sit in, move around, and stand outside of your car during wireless charging without any concern whatsoever. Even the FDA performed measurements with pacemakers (also called cardiac implantable electronic devices or CIEDs) to show there is no effect there either. On the other hand, have you ever thought about how dangerous it can be to bump a gasoline vehicle’s exhaust pipe? Exhaust pipes can reach staggeringly high temperatures beyond what even your oven can attain. No need to worry about that kind of safety issue with an electric vehicle being powered wirelessly!
And let’s end talking about microwave ovens (of course!)
Lastly, there’s always the question of comparison to microwave ovens. How is it that a microwave oven can heat up water and food and yet a wireless EV charging system transferring much more power won’t have any effect? To understand this, it is important to know that microwave ovens typically operate at a frequency of 2.45 gigahertz whereas EV wireless charging systems typically operate at 85 kilohertz. The ratio of frequencies is several orders of magnitude (i.e., ~28,823 times), and this matters. Microwave ovens use this ultra-high frequency because, at very high intensities, 2.45 gigahertz interacts weakly with liquids and causes the liquid molecules to vibrate and heat up. Lower frequencies, like those used for wireless charging, don’t interact appreciably. However, even a microwave oven is required to contain that extremely high intensity electromagnetic field and ensure that rf exposure limits are met outside the microwave. An EV wireless charging system is nothing like a microwave!
Happy ending…
In summary, WiTricity’s wireless charging for your electric vehicle will seem like magic. No need to worry about tripping over or touching those dirty cords, forgetting to plug in, or even thinking about how it works. You can sleep “safe and sound” knowing your EV will be ready for your trip tomorrow!
For more detailed information, you can see my interview on Innovation News Network.
Ky Sealy is an Engineering Fellow at WiTricity. He is a world-renowned expert in the field of wireless power transfer and is currently involved as an expert or in a leadership role in multiple standards organizations such as SAE, IEC, CISPR, ITU-R, AirFuel Alliance, and others. Ky represents the United States as a wireless power expert and delegate for many of these standards and consults administrations on related matters including electromagnetic emissions, compatibility, and exposure amongst other topics.
