Shielding the wires
The place where the big changes begin is in the wiring. Suddenly, vehicles are carrying massive amounts of current. Features that used to run on a measly few amps have been boosted to 100A, 200A, and even higher. The upshot is that more copper is needed to handle the additional current, and more shielding is needed on the cable to prevent electromagnetic interference (EMI).
Cables, which in most cases had a cross-sectional area of about 25mm2, are now looking at more than 75mm2. To put it another way, wire diameter has jumped from about one-eighth of an inch to three-fourths of an inch.
"The wires are much, much bigger," Rand Wilburn, global marketing manager for the cable and interconnect supplier Molex, told us. "It's not only the amount of copper in the cable. It's the amount of shielding that it needs."
Delphi's Shield-Pack HV 280 incorporates a high-voltage interlock (HVIL) to protect mechanics and first responders from high voltage.
(Source: Delphi Automotive)
For engineers -- who are already struggling to find space around the engine, transaxle, and traction motor -- the prospect of thicker cables raises yet another packaging issue under the hood. Now they must consider how to route the cables, which have a wire braid or foil around them and therefore are less flexible than their skinny predecessors.
And that's where the issue of shielding must come in. Engineers can't afford to have current-carrying cables emitting EMI, and they can't afford to let the electrical noise come in, either.
"You've got a lot of electrical systems within the 'brain' of the car," Wilburn said. "That's why the shielding is necessary. Any time you put those kinds of voltages and currents through a wire, you're going to potentially create electromagnetic interference."
Dealing with interconnects
Suppliers say the braiding and foil around the cable help mitigate EMI. But what's often lost in the discussion is that it's equally important for interconnects to have the shielding, as well as larger size. There are a variety of reasons for this, not the least of which is the fact that they must deal with thicker, braided wires.
electric cars has certainly changed the electrical system of vehicles. the old 12v model has bigger range and Im looking forward to see low cost alternators and batteries and I believe it wouldn't be impossible.
Oh, I forgot an important point: anither compelling reason for the very high current rating is for FAST CHARGING reasons (so-called "Level 3" or 30-minutes for a full recharge), not so much for running the motor(s), even for a racing vehicle!
For years now, the operating temperature requirements for electronics in the engine compartment has been the "old" MIL-spec range of -40 to +125 C! Vehicles are expected to start and run from a (very!) cold start near the poles, and also to operate fine with engine compartment temps way above boiling water. Typical IC engines are designed with optimal running block temp around 110C. Before jumping into the automotive industry some years ago, I had done a lot of extreme hi-rel electronics design (both MIL and CO-grade telecom and 911 call centers), and the auto requirements made that look easy!
Re the "wattage" comments: just because a relay is rated for X volts and Y amps does NOT imply a capability of controlling an XY-watt load! Switching devices have multiple ratings (especially with inductive loads like big motors): carrying capacity and interrupting capacity are only two of the parameters, and both may have separate limits for V, A, and VA.
I also remember that at least 20 years ago, the UNANIMOUS agreement in the auto industry was that the "ancient" (e.g. late 1950s) 12VDC (incidentally, it's really 13.8VDC nominal) would soon be replaced by "24V" or maybe even 40V batteries and alternators, for multiple reasons including reducing the weight of all that copper whose usage was going up rapidly as electronics took over more and more of the subsystems of the vehicle! I guess nobody remembered their basic physics (if they ever learned it); INERTIA applies to many areas, even the marketplace!
Where is all this power going? For example, there was mention of a device rated 900v/500a continously, nearly half a megawatt, roughly 600HP! Really? This flies in the face of efficiency, the usual reason for being of electric vehicles.
I'd have imagined the higher voltage is employed to reduce amps, copper, and weight, but there's little mention of that here, in fact the emphasis is on high voltage and amperage.
I'd love to see cars go to a 24v primary battery, cutting existing amperages and wire sizing in half. This is considered an inherently safe voltage to handle with your bare hands. (Not that you should.)
Finally, even these higher voltages have been used for a century or more routinely in industry, I'd expect protection schemes there will crossover, with modifications for compactness and lightness. I've been working with them my entire adult life, and I'm close to retirement.
This is getting wild. I understood the capaciter style battery fell out of favor because of the potential of dangerous discharge. This brings us right back.
I realize the article is about the shift to higher voltages in automotive electrical systems, but the "history" portion at the top of the article makes no sense at all, particularly this line: "When the battery alone wasn't powerful enough, engineers augmented it with an alternator and a fan belt."
There was never an automobile that included a battery but provided no means to charge it. Some very early ones had a magneto for the spark, a hand crank for starting, and carbide lamps for headlights, but as soon as the magneto was replaced with a coil-and-points ignition system, a generator was needed to charge the battery. In fact, some early vehicles had generator-driven electric lights before they had an electric starter or a battery.
Also, if one is writing a brief history of automotive voltages, it should be mentioned that all military vehicles since about 1950, and some heavy civilian vehicles throughout that time period, have used 24 volt systems for exactly the same reason higher voltages are being used today -- to reduce the amount of copper needed to carry high power levels.
As far as the safety issues go, I think the only way we're going to get anywhere without prohibitive expense and inconvenience is if we accept that the standard of comparison be "no more dangerous than a tank of gasoline" rather than "can't possibly be hazardous under any circumstances".
Trawickim had some interesting observations. The safety feature that disconnects the battery reminds me of the fuel pump shutoff switches on some cars. Even the 12 Volt batteries should have some means of disconnecting. I'm reminded of a car fire that was extingushed only to reignite because of a short in the wiring. The fire extinguishers ran out before the battery did and the car was a total loss. Some industrial machhines have an emergency stop button that kills all the power. If you adjust the nuts and bolts on your battery connectors, you can push them down onto the battery post with a twisting motion and they will lock into place. You can also pull them back off in case of an emergency. If you have side posts, oh well. Pete O.
In developing hybrid construction equipment, inverters are now using 800 VDC capacitors and the bus takes several minutes to reduce to a voltage that isn't deadly. So, future accidents are highly likely. However, you can't force a new technology without hazards especially when consumers need the new product to perform to the exact same specification as the traditional product.
From Dell / Intel® New Paradigms in Design Work Scott Hamilton, vertical market strategist for Dell Precision workstations, 5/2/2013 3
Early in my career, I worked as a draftsman and remember the days of drawing on vellum with numbered pencils and Mylar with plastic lead. This was a fun experience in the sense that I ...
I've been using workstations for more than 10 years and love finding ways to get more performance from my system. With demanding professional applications that require more power each ...
A lasting memory from my first job as an engineer in an auto assembly plant is standing on hard concrete at six in the morning, vending-machine coffee clutched in hand, listening to ...
A quick look into the merger of two powerhouse 3D printing OEMs and the new leader in rapid prototyping solutions, Stratasys. The industrial revolution is now led by 3D printing and engineers are given the opportunity to fully maximize their design capabilities, reduce their time-to-market and functionally test prototypes cheaper, faster and easier. Bruce Bradshaw, Director of Marketing in North America, will explore the large product offering and variety of materials that will help CAD designers articulate their product design with actual, physical prototypes. This broadcast will dive deep into technical information including application specific stories from real world customers and their experiences with 3D printing. 3D Printing is
To save this item to your list of favorite Design News content so you can find it later in your Profile page, click the "Save It" button next to the item.
If you found this interesting or useful, please use the links to the services below to share it with other readers. You will need a free account with each service to share an item via that service.
Tweet This
11 
