http://www.autospeed.com/cms/A_1450/...popularArticle

Yes, I know it is an older article, 2002, it is well written and may be new to some folks.

Bob Wilson

 

Thank you for the good article, but there are some errors need to be corrected.
Toyota says it is series/parallel hybrid system.
http://www.toyota.co.jp/en/tech/envi...ths2/what.html
The maximum engine power and the maximum motor power don't perform at the same time, therefore we can't add two of them.
The maximum system power is 65kW.
http://www.toyota.co.jp/en/tech/envi...hs2/speci.html
None can supply such huge 351 amperes, probably approx 100 ampares.
The VVT-i engine does not change the exhaust valve timing, therefore the expansion stroke is as same as a conventional engine.
So, the expansion stroke is nothing related to the Atkinson cycle.
The specification paper says the compression ratio is 13.0:1, but it never goes to the real 13.0:1 ratio.
The intake valles closed very late during the compression cycle, and some intake air blew back to intake manifold.
Then, the real compression ratio becomes approx 9.5:1 or so.
That's how the Atkinson cycle and the VVT-i work!

Ken@Japan

 

Hi Ken,

It as an older article and I didn't read the technical bits closely. Just a couple of observations:

• maximum system power - the line in the table above "Output at 85km/h" shows "Maximum output in kW(Ps)/vehicle speed km/h" and shows a higher value, "74(101)/120 or higher." This would be 74 kw at speeds above 74 mph (120 km/h).
• Julian comes from a traditional engine background where compression ratio is the same as the expansion ratio. We know better, compression ratio is not the same as expansion ratio, but given his background and 2002, I'm not too surprised he missed that one.

Compared to some of the stuff we've seen in other publications, this wasn't too bad. Still I am curious how Julian came up with the 351 A. when discussing 350 Nm of torque. For a single wire, 351 A. would take some serious copper, AWG 0000, 0.46 in. / 11.7 mm. diameter! This would be more in line with the total current from multiple windings.

Bob Wilson

 

Hi Ken,

Julian corrected the maximum power output to 74 kW. However, he reports the 351 A. came from a Toyota source that was available at the time. I didn't address your other concerns because I'm not really invested in 'hybrid architecture.' As for the Atkinson cycle, I really hadn't taken a close look in this article since I think we're on the same page about compression and expansion ratios.

I have tremendous respect for Julian and the quality of his writing. Unlike some, he is a responsible journalist with serious engineering credentials. His is the only auto journal I could ever recommend. <grins>

Bob Wilson

 

I see. I stand corrected.
Let's assume the voltage is approx 250V reducing some value from the nominal 273.6V.
The power is 351A X 250V = 88kW
None can supply such huge 88kW.
The max power from battery is approx 20kW.
In other words, the output power at the max torque range is approx 10kW, then we'll see 78kW (88kw - 10kw) heat loss if the 351A was correct.
The motor will be burnt out instantly.

Ken@Japan

 

This is one of those cases where I'm scratching my head too. One speculation is a capacitor initially discharged into stator windings might do it but 351A, even through an IBGT, would be an impressive feat. The stator winding would initially hold off on the maximum current flow but you still would have that brief peak.

I've got a Fluke, clamp-on, DC meter but it only goes to 100A full scale. Even some of my earliest measurements with home-made, clamp on coils does not show a huge, startup spike:

Some of the initial startup loads:

During the initial startup, the inverter uses pulse-modulation to prevent excessive current flow. You can see that in this trace:


I don't see 351A in my data but IBGTs handling these power levels are available and were considered according to:I remember one of the earliest Toyota SAE papers about the NHW10 discussing the use of pulse modulation in the initial startup to prevent excessive startup currents.

Bob Wilson

ps. Julian pointed out he didn't write that particular article.