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#34 Salvage auction

Jaff

Active Member
Aug 15, 2010
3,135
326
Grimsby, Canada
Nice job Marco!...Psst, please let us know when you fit the liquid cooling units for the motor and PEM and get the 0-60 times down to 2.5 seconds...many of us will be beating the proverbial "path to your door..." :wink::smile:
 

marco2228

Roadster Signature #34
Nov 19, 2010
211
55
Cologne/Bremen , Germany
Awesome Job Marco! While your at it, change out the stock brakes for CarboTechs and also remove the old brake fluid, clear out the lines, and put in new clean stuff. I'm sure that brake fluid is long over due and has a good bit of moisture in it. I also removed those silly sun visors, you get more visibility without them.

Thanks for sharing your ideas:)
I called CarboTech in the UK, today. Their brakes have too much performance to be street legal in Germany:D
Well, I think my front brakes might have been upgraded already? They have "AP Racing" written on them. Is this the stock front brake in the 1.5 Roadster?
Frontbrake.jpg


Good idea to remove the sun visors, as I am 1.93m tall. I'll probably just pull them off their mounting and put black bushings around the pins so I can put em back on, if I want to.

Ok, some photos of the PEM.

This is the charging area in the PEM. You see the bent and twisted PEM case.
Charge circuit.jpg


This are two of the three power stages
Power stages.jpg


The circuit board on the left is the brain of the PEM, on the right the fan controller for the PEM and motor fans.
DMC & Fan control.jpg


There have been several errors, but this is probably the most interesting one.
This photo shows one of the three power stages. You can see the IGBT's on it. 21 of the 28 were dead. Because of the manufacturing tolerances, the IGBT's which are connected in parallel (four groups of seven) have to be matched. Because it's hard to measure in the circuit and the ones that still seemed to be good might have been damaged too, I replaced them all.
Damaged IGBT's.jpg


"Measuring device" to match the IGBT's at 55 A current.(that simulates a PEM output power in the car of >250 kW)
Testsetup.jpg


New IGBT's at their new job (not soldered in properly at the photo)
New IGBT's.jpg
 
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PV4EV

Member
Supporting Member
Oct 26, 2011
573
793
Area 51(a) / UK
I called CarboTech in the UK, today. Their brakes have too much performance to be street legal in Germany:D
Well, I think my front brakes might have been upgraded already? They have "AP Racing" written on them. Is this the stock front brake in the 1.5 Roadster?

Thanks for the PEM pictures - fascinating .. But not sure why a replacement PEM is $17,000 (as told by service dept ..)

Meanwhile heres a photo of my Roadster 2.5 front brakes on day one of ownership. But I do not know what was standard on a 1.5.


 

marco2228

Roadster Signature #34
Nov 19, 2010
211
55
Cologne/Bremen , Germany
Thanks for the PEM pictures - fascinating .. But not sure why a replacement PEM is $17,000 (as told by service dept ..)

Meanwhile heres a photo of my Roadster 2.5 front brakes on day one of ownership. But I do not know what was standard on a 1.5.



Ok, thanks. That looks quite similar.

Nice job Marco!...Psst, please let us know when you fit the liquid cooling units for the motor and PEM and get the 0-60 times down to 2.5 seconds...many of us will be beating the proverbial "path to your door..."

Haha, I had some thoughts about that and almost bought a 2nd PEM to try it, but than the seller raised the price for the PEM by 100%. Well, he's still sitting in the PEM.
If he'd drop the price again I'll put that PEM in the car, so I could play around with the repaired PEM.

The main problem with liquid cooling is that the heatsinks of the power stages for the three phases have to stay electrically isolated. Another idea would be CO2 cooling...
 

tom66

Member
Dec 17, 2013
625
28
United Kingdom
Wow! I'm amazed by how few IGBTs are needed for such high power. What IGBT do they use? I'm quite surprised they did not use high power IGBT modules. The Megapoles are so compact - I can now see how Tesla managed to fit them all into the Model S' cylindrical drivetrain assembly. With some IGBT upgrades, higher battery voltage, and of course liquid cooling, you could easily pump out 350kW over all three phases with a similar design. I bet they're in a triangular arrangement and the circular case is just for cooling and packaging efficiency.

I'm really impressed by the engineering in the PEM. That looks absolutely top class professionally engineered. Not a single bodge wire! On something they made fewer than 3,000 of, that's pretty rare...!

One of the things that is interesting is I see a TI DSP for the motor control, but I was half expecting a secondary monitor processor for safety. Perhaps that Xilinx device (CPLD/FPGA?) is a hardware interlock to prevent the DSP going out of control.

Also interesting how the Megapoles appear to be similar between phases; looks like you could swap them around for test purposes.

I'm quite surprised there isn't any glue around the larger components and SMD caps - kind of surprising as they can be vulnerable to vibration and fall off the board. Also, they didn't use automotive rated components: just 105°C standard in most cases. If the PEM is aircooled, this might work out well (well, for anything not switching 200kW+ that is...)

It'd be really nice to see some close up chip shots to understand what each part is :)
 

wiztecy

Active Member
Apr 29, 2012
2,905
566
Santa Cruz, California, United States
I called CarboTech in the UK, today. Their brakes have too much performance to be street legal in Germany:D
Well, I think my front brakes might have been upgraded already? They have "AP Racing" written on them. Is this the stock front brake in the 1.5 Roadster?

Really, its illegal to have good brakes in the UK? That's the craziest thing I've ever heard in my life. The CarboTech BobCat 1521 were designed for the street, I'm running the AX6's which are the track pad. Roadster owners who've switch to either are very pleased and its a night/day comparison over the stock Brembos that have a terrible time stopping the Roadster. They're also dusty as a muck and that also contributes in their stopping power even worse. So how would they know that you swapped them out, does the UK have vehicle inspections every year? If its a matter of just ordering them, order them in the US and have them shipped out. Or you could have one of your forum friends send a set out to you.

As for the brake calipers and the AP Racing branding, my 1.5 is equipped with the same ones.
 

mg012

Member
Sep 26, 2012
107
0
San Antonio, Tx
CarboTech brakes

Really, its illegal to have good brakes in the UK? That's the craziest thing I've ever heard in my life. The CarboTech BobCat 1521 were designed for the street, I'm running the AX6's which are the track pad. Roadster owners who've switch to either are very pleased and its a night/day comparison over the stock Brembos that have a terrible time stopping the Roadster. They're also dusty as a muck and that also contributes in their stopping power even worse. So how would they know that you swapped them out, does the UK have vehicle inspections every year? If its a matter of just ordering them, order them in the US and have them shipped out. Or you could have one of your forum friends send a set out to you.

As for the brake calipers and the AP Racing branding, my 1.5 is equipped with the same ones.

Where did you get your CarboTech brakes? Do you have specific part numbers for the Roadster?

thanks
michael
 

Doug_G

Lead Moderator
Apr 2, 2010
17,883
3,392
Ottawa, Canada
Front Carbotech CT 109L AX6
Rear Carbotech CT 491L AX6

Got mine from 949Racing, but it's probably just as easy and faster to go directly to Carbotech.
 

spaceballs

Member
Sep 17, 2013
647
132
Sammamish
From what I can tell the current IPM/IGBTs do not match the smaller high switching IGBT's that Tesla uses.

Marco, that's great that you got your PEM working again. IGBT's have progressed along way since that Roadster was designed. From a few minutes of looking, you can get a single 1200V, 300A IGBT for less than $150. If you want a real beast of an IGBT, you can you get a 1200V, 1000A IGBT for $650 (http://theelectrostore.com/shopsite_sc/store/html/cm1000ha-24h-powerex-new.html). To put it in perspective, 1200V * 1000A is 1608.6hp.
 

tom66

Member
Dec 17, 2013
625
28
United Kingdom
Large hybrid modules also can't match the speed of many-parallel IGBT arrays, which is probably why Tesla used this setup. Looks like the drive waveforms are sent into two groups individually, which makes sense, to reduce the gate capacitance the driver ICs have to charge/discharge.

In quantity, Tesla was probably buying each IGBT for less than $5 a pop, which is far cheaper than a single IGBT half bridge module ($400 ~ $1000+ per unit) even if you need 28 IGBTs...
 

qwk

P130DL
Dec 19, 2008
3,024
856
Large hybrid modules also can't match the speed of many-parallel IGBT arrays, which is probably why Tesla used this setup. Looks like the drive waveforms are sent into two groups individually, which makes sense, to reduce the gate capacitance the driver ICs have to charge/discharge.

In quantity, Tesla was probably buying each IGBT for less than $5 a pop, which is far cheaper than a single IGBT half bridge module ($400 ~ $1000+ per unit) even if you need 28 IGBTs...

The roadster uses 84 IGBT's. At $5 a pop, that is still only $420.
 

tom66

Member
Dec 17, 2013
625
28
United Kingdom
Yep, indeed - part of Tesla's low cost technology.
Also, it looks like every part on that board is commodity, off the shelf. Compare to the Prius, for example, which has a large number of custom Toyota chips.
 

qwk

P130DL
Dec 19, 2008
3,024
856
Yep, indeed - part of Tesla's low cost technology.
Also, it looks like every part on that board is commodity, off the shelf. Compare to the Prius, for example, which has a large number of custom Toyota chips.
Yes, this is really a great thing, because it allows much easier DIY repair of electronic components.
 

jory

Member
Sep 27, 2011
223
2
san francisco
The main problem with liquid cooling is that the heatsinks of the power stages for the three phases have to stay electrically isolated. Another idea would be CO2 cooling...

for low (unit) volume applications, i'd consider using one of the variants of 3M flourinert as the cooling fluid. i've previously utilized it as a pressure compensation liquid (in conjunction with a bellows) for the electronics compartment of an deep sea oceanographic instrument i designed/deployed many years ago.
 

Doug_G

Lead Moderator
Apr 2, 2010
17,883
3,392
Ottawa, Canada
Large hybrid modules also can't match the speed of many-parallel IGBT arrays, which is probably why Tesla used this setup. Looks like the drive waveforms are sent into two groups individually, which makes sense, to reduce the gate capacitance the driver ICs have to charge/discharge.

Right, for IGBTs and MOSFETs it's very important how you drive them. It can actually take quite a bit of oomph to drive them fast and hard enough; otherwise they partially conduct and dissipate a lot more power. They really like to be all the way on, or all the way off. Anything in the middle just generates lots of heat.
 

hcsharp

Active Member
Jun 7, 2011
3,427
1,513
Vermont
Right, for IGBTs and MOSFETs it's very important how you drive them. It can actually take quite a bit of oomph to drive them fast and hard enough; otherwise they partially conduct and dissipate a lot more power. They really like to be all the way on, or all the way off. Anything in the middle just generates lots of heat.

What's the typical solution to drive lots of stacked IGBTs? Opamp or ??? Based on the article in Tesla's blog (which has a picture of a 2.x PEM) they are switching at a frequency of 32 kHz. That's enough to generate a lot of heat.
 

tom66

Member
Dec 17, 2013
625
28
United Kingdom
What's the typical solution to drive lots of stacked IGBTs? Opamp or ??? Based on the article in Tesla's blog (which has a picture of a 2.x PEM) they are switching at a frequency of 32 kHz. That's enough to generate a lot of heat.

A dedicated IGBT driver IC, such as http://www.irf.com/product-info/datasheets/data/irs21850spbf.pdf

These combine the level shifting and high current output drive in one IC, the driver typically floating up to VBAT above ground.

The rest of the ICs on there will probably be checking for anomalous states such as both channels turned on at once and supply voltages dropping low causing poor conduction.
 
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lolachampcar

Well-Known Member
Nov 26, 2012
6,106
7,452
WPB Florida
jory,

I too used Flourinert to make a version of our tablet for diving. It worked wonderfully simply using the 10" diagonal display cover glass as the bellows (but then we were looking at 150' or less) :) Neat stuff.
 

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