Teardown of Chevy Volt inverter assembly - Page 1
Forum section: electronics / general

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: February 07, 2018, 05:19:28 pm
content: It's more of a 'build-up' than a teardown, which has a nice side effect that the interesting bits are all at the beginning. Amazing power density, at least for someone who doesn't work with power electronics for a living.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 07, 2018, 08:19:06 pm
content: Quote from: radar_macgyver on February 07, 2018, 05:19:28 pmThe power density is amazing no matter who you are. That is especially true when you consider that expected lifespan, safety regulations, and cost pressure applied the engineering challenge.The part that I would buy a ticket to see is the test and validation of these types of systems. The voltage and current involved is very high and it is facing an extremely dynamic range of operation. The control systems have to be over the top outstanding to make it all work.Interesting there is a thermocouple on each IGBT (and presumably current sense). Curious if an IGBT fails, if the system as the ability to continue at reduced power.

author: John Heath
author_rank: Frequent Contributor
timestamp: February 15, 2018, 12:36:39 am
content: Cool video. Thanks for sharing.

author: JohnG
author_rank: Frequent Contributor
timestamp: February 15, 2018, 08:04:01 pm
content: This is truly a fine example of commercial engineering. The amount of engineering going into the power module alone is astounding. Not only are there a lot of carefully placed bond wires, note that each has relatively sharp bends to keep the length down. If you look carefully, you can see that the module is filled with clear gel, which not only forms another layer of protection, it also provides electrical insulation, and improves the surge rating by helping to cool the bond wires. Note also the size of the single IGBT die.Note that these modules do not have to last a particularly long time. For example, 200k miles at an average speed of 40 mph = 5000 hours. However, the transient electrical and thermal environment is brutal, with large and frequent excursions in power and temperature. There is a great deal of engineering effort just to keep the IGBT die attached to the module baseplate.Thanks for sharing this!John

author: rx8pilot
author_rank: Super Contributor
timestamp: February 15, 2018, 08:27:57 pm
content: It is hard to imagine the transients involved - simply huge. The control subsystems have to be near miracle levels of engineering to keep that under control.I marvel at the display on my own Chevy volt that displays Kw - when I drop the hammer it goes from 'idle' of 1kW to full acceleration of 150kW. The Teslas are triple that number or more.

author: floobydust
author_rank: Super Contributor
timestamp: February 16, 2018, 01:09:52 am
content: I did get a chuckle at Chevrolet's implementation.Hitachi did the inverter electronics, made in Japan.Using a custom IGBT module- whereas Tesla uses discrete TO-247's.Transaxle fluid pump module? Tesla is direct drive, no tranny.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 16, 2018, 02:31:00 am
content: Not a big deal, I've been building current mode, fully protected supplies for, gosh, over a decade I suppose. A basic motor drive (the most basic to control, a PMDC machine I suppose) only takes an SMPS scaled up, making sure to add important protection features -- desat detector, overtemp, water flow (if water cooled), and anything else mechanical related.To do a proper BLDC or induction drive (higher efficiency and power density), you need more phases (potentially many more, because you have the option of 3 (or more) level inverters), and you need a more refined control, usually something vector based. It could be basic PWM, but efficiency can be gained with more advanced adaptive/predictive methods to reduce rate of switching edges.Make no mistake -- that one module isat leasta million dollars of engineering. Probably ten. Design would've started with breadboard prototypes, then design prototypes, then production prototypes, and finally production. When you're making a million of something, it doesn't even stop there: there is production engineering, from securing the supply chain, to the logistics of getting everything in, on time, every time.There is absolutely, positively nothing impossible about this design -- I mean, obviously given it exists -- but it's clear, to me at least, where to begin and how to complete development of such a beast.I'd love to do a design like that, myself; but I'm lacking some knowledge to do a comprehensive design, so some time would have to go to learning that; not to mention, the obvious and more pressing problem, that it would take me personally about ten man-years to finish the design! Part of the cost of these things is organizing a few dozen engineers to work on the various parts of it, so it can be completed in a reasonable time frame (maybe a year).Related: when he showed the bus bar I said to myself, "that looks just like something Methode would make." Turns it over, see the sticker... hah.Incidentally, it looks like that module uses just basic 3-phase 2-level inverters. Gate drive probably supplied by a many-output DC-DC converter, one of those gate drive controller ICs (like that ACPL-3xx I think) with external switches, and the switches are SOT-223 or TO-243 transistors at the gate terminals.Regarding the IGBT modules, those didn't come out of nowhere -- they've been around for many years, I suppose originating with hybrid circuits going way back. Die bonded assemblies are 100% normal in industry, and if this isn't an off-the-shelf part, it's custom designed for GM (which is absolutely believable). I'm impressed by how many bond wires they needed, but, I mean, there you have it, that's what they need for that many amps.Tim

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: February 16, 2018, 05:44:35 am
content: Quote from: floobydust on February 16, 2018, 01:09:52 amThe same channel has a video about the Volt's transaxle, which is needed since it's a hybrid (despite GM calling it a range extended BEV). The Bolt's drivetrain is much more like a Tesla's (fixed 7:1 reduction). They should have teardowns of the Bolt's systems coming up shortly.

author: JohnG
author_rank: Frequent Contributor
timestamp: February 23, 2018, 12:17:51 am
content: Quote from: blueskull on February 16, 2018, 01:35:51 amThat's very true. However, I first heard of silver sintering as a solder replacement for die attache about 20 years ago. It took a lot of effort and many years to make it a commercially viable process.John

author: lem_ix
author_rank: Regular Contributor
timestamp: February 23, 2018, 02:11:40 am
content: Drool ... wanna work on a design like thatThen again more electric cars in the future so who knows

author: JohnG
author_rank: Frequent Contributor
timestamp: February 23, 2018, 02:43:25 pm
content: Quote from: blueskull on February 23, 2018, 02:18:25 amI remember that it was coming, and I think Infineon has been using it for some time. But, I have not had any involvement in module design for 5 years or so. Even then, I was not directly involved in the mechanical side of things. Are the existing turn-key solutions heat-sintering only, or is pressure involved?

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: February 25, 2018, 09:12:48 am
content: Not sure how you'd faultfind a module like that, when the power connectors overlay it so there is no access at all when powered.I can see this being a problem with EVs a few years down the line when they start to develop electronic faults and the only fix is the 'throw money at it' approach -changing modules at massive cost,hopingthat will cure the fault. Likely most owners will decide that the cost, coupled with no certainty of fixing the fault, mean that it gets scrapped.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 25, 2018, 07:05:42 pm
content: Quote from: IanMacdonald on February 25, 2018, 09:12:48 amThis is why I leased my Chevy Volt. I don't trust that it will be stable, reliable, or worth anything after 36 months.

author: JohnG
author_rank: Frequent Contributor
timestamp: February 25, 2018, 07:35:20 pm
content: Quote from: IanMacdonald on February 25, 2018, 09:12:48 amPower modules can be made to be very reliable. The very same technology is used for wind turbines, MW solar inverters, locomotive traction drives, and the like, where downtime and repairs are really expensive. And, many cars have gotten more reliable and longer lasting with the addition of electronics. That doesn't mean all cars are, but it means that it can be done properly and reliability can be improved.Also, an IGBT failure in a module is not that hard to diagnose - there are current, voltage, and temp sensors all over the place.John

author: floobydust
author_rank: Super Contributor
timestamp: February 25, 2018, 09:33:53 pm
content: Locomotives, Prius etc. use rubber vibration mounts for the inverter.Chevy mounting IGBT modules on an internal combustion engine, what could go wrong. Those bonding wires will take the vibration, right?

author: rx8pilot
author_rank: Super Contributor
timestamp: February 25, 2018, 11:53:48 pm
content: Quote from: floobydust on February 25, 2018, 09:33:53 pmIsn't the assy filled with a soft material that diffuses the vibrations? Pretty safe to guess that this unit was exposed to considerable simulation and actual vibration testing with big margins of safety.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 26, 2018, 12:11:30 am
content: What a frightful thing it must be to put one of those modules in an aircraft APU, or a missile/rocket for that matter.Yeah, they have ways of dealing with that, no problem.Tim

author: floobydust
author_rank: Super Contributor
timestamp: February 26, 2018, 04:41:53 am
content: My point is it's the worse possible location for electronics, which are not MIL qualifiedIntegrating the electric motors, inverter, mechanical diode, transaxle, internal combustion engine etc. seems a bit bizarre, aside from lowering initial cost - it's a mechanic's nightmare.We should gush over this technology? Nobody knows what replacing the "F module" costs, looking at the true cost of ownership.Then I got surprised by all the issues the vehicle hasGen2 Volt Issues, it kinda made me sour.The new 2017 motor seems to be the bulk of the progress, at reducing rare-earth metals.

author: mtdoc
author_rank: Super Contributor
timestamp: February 26, 2018, 05:29:55 am
content: Quote from: floobydust on February 26, 2018, 04:41:53 amSo your point is that you know better than the Volt engineers and you speculate that some day Volts may have a problem because of that? OK....As far as some issues some owners have had with their Volts - Duh. Name me a car that this is not true of. No automobile is without some issues. The fact is overall the Gen1 and Gen2 Volts have proved very reliable with very high customer satisfaction ratings. Most owners have had zero issues and many have driven over 100k miles. While I haven't put that many miles on mine, I've had it for 3 1/2 years and have had zero issues.Any theoretical future repair costs will easily be offset by the thousands of dollars I've already saved on gasoline, the savings on very infrequent need for oil changes (once every 2 years) and very, very rare brake servicing (I don't anticipate needing any brake servicing until > 100K miles).BTW, here is a good in depth lecture on the Volt's electronics engineering.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 26, 2018, 06:05:47 am
content: I have a gen 2 Volt Premiere and really like it. No issues at all. As a daily driver.....great car. For a four-door family car it has a surprising amount of fun.

author: schmitt trigger
author_rank: Super Contributor
timestamp: February 26, 2018, 06:35:54 pm
content: Quote from: T3sl4co1l on February 16, 2018, 02:31:00 amValidation and compliance testing on its own would be a million dollars easily.The automotive industry is very familiar with litigation caused by a faulty device, the cost of its recalls, and the negative impact on a brand. Ford Explorer, anyone?As such, they must have tested the safety of this module for every conceivable problem, even customer induced ones....that would have been very expensive.

author: JohnG
author_rank: Frequent Contributor
timestamp: February 27, 2018, 02:16:38 am
content: For those who wish to understand a small bit of what goes into design for reliability of automotive electronics, please start here:http://www.aecouncil.com/AECDocuments.html. It is not easy to get parts and systems qualified for automotive use, but the market is large, so there is incentive to do so.Power modules of the sort you see are not a new idea - they have been around for many years, and have had a great deal of refinement over that time.Also understand that any modern automobile will not run properly or at all without rather sophisticated electronics, both analog and digital, under the hood, next to or even mounted on an internal combustion engine. Car companies already spend millions qualifying electronic components, so this is not new to them.John

author: schmitt trigger
author_rank: Super Contributor
timestamp: February 27, 2018, 04:47:20 am
content: My point exactly, John.Those of us who are somehow related to the automotive industry, have a sincere appreciation for the amount of engineering work that goes into these units. And its associated cost, too.The stakes are immense.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 27, 2018, 04:54:35 am
content: If I had to guess - $1mil seems like a tiny number for this type of thing. The burn rate of the team and the infrastructure to support them all is big numbers. Perhaps 10's of millions or more?

author: jmelson
author_rank: Super Contributor
timestamp: February 27, 2018, 10:18:32 pm
content: Quote from: IanMacdonald on February 25, 2018, 09:12:48 amThese things are amazingly reliable. We have had 4 hybrids in the family. One got wrecked when my son ran over a semi tire. The guy in front of him managed to hit it with his wheels, and probably had a repairable wreck. My son had no warning, and ran over it down the center. It ripped off the engine and transmission oil pans and tore up all the stuff in the center tunnel. Totalled the car.But, other than that, our 2 honda civic hybrids and remaining toyota prius have never had any electronic problems. The Honda civic hybrids have both had hybrid battery replacements. Who at Honda thought you could put 120 NiMH D-cells in series and pull and push 100+ amps through them, for years, with no cell balancer? Crazy!

author: saike
author_rank: Regular Contributor
timestamp: March 07, 2018, 07:21:17 pm
content: Here is something I saw when looking for a new vehicle to buy.It gives some idea of the sums of money involved.https://www.greencarreports.com/news/1093244_2016-chevy-volt-to-get-more-efficient-less-expensive-inverterAll I can think when I see this is, a 1$ component failure in there means a $5000 repair bill. I have just given up on one vehicle (non electric) and sold it because of an intermittent electrical fault that stranded me one too many times.

author: mtdoc
author_rank: Super Contributor
timestamp: March 07, 2018, 07:50:21 pm
content: Quote from: saike on March 07, 2018, 07:21:17 pmWelcome to the world of modern vehicles. Such concerns are not limited to EVs.Keep in mind that on the Volt the Voltec warranty is good for 8 years and 100k miles and covers the inverter, battery and other hybrid specific components. Of course, even more extended warranty coverage is also available at a price...

author: bicycleguy
author_rank: Frequent Contributor
timestamp: March 10, 2018, 02:22:17 am
content: Quote from: T3sl4co1l on February 16, 2018, 02:31:00 amBrings back memories, as an ME in electronic packaging, worked on EV IGBT for EV1 in mid 1980s? This was just after GM bought Hughes Aircraft. But about that million dollars, just like any technology, you try not to forget the past and build on it. Attached is what we were doing back then. Frankly, it doesn't look like they've made all that much progress. We were doing thermal stress analysis of the large silicon die attachment. The picture, just taken is of a never lidded IGBT thats been in my desk and various bins for 30+ years. Still looks good! I think this one had aluminum silicon carbide composite heat spreaders.Do remember that GM was quite ruthless. They would assign similar tasks to us California military-aerospace engineers and local Detroit engineers. In the reviews the Detroit guys got to see what we were up to, but we weren't allowed to see much of their work or know the overall picture. They would pick the best of whatever we came up with. Did the same with vendors. Wasn't to sad when they sold us to Raytheon. Hitachi may make their current IGBT but I can tell you GM is steering the design.

author: schmitt trigger
author_rank: Super Contributor
timestamp: March 12, 2018, 08:19:04 pm
content: bicicleguy;You are correct. Good engineering holds itself up for several decades.In particular, I have lots of admiration for the West Coast aerospace companies. Some of their airframe designs made in the 1960s are still viable platforms 50 years later.