The Drive-a-Toyota Act
in [Toyota]
|
From: Bill Putney on 7 Jul 2007 07:51 Bill Putney wrote: > ...In reality, I would not be surprised to find out that what they use and > call a "generator" is actually more like what you and I commonly refer > to as an alternator. I would also suggest that there is a bit of > electronic processing done on the raw output of the waveform that comes > out of this spinning device as to muddy the difference between what you > and I think of as generators and alternators and their traditional > differences such that we might have trouble deciding which category in > traditional terms whatever is in the Prius really fits into. In > addition, it would blend with the manufacturers tendency to now call > alternators generators anyway. I should clarify here that there is an almost-unmuddiable aspect of the alternators and generators (using the terms in the traditional pre-90's automotive sense). That is that the generator will have a commutator (to switch current in the windings as it rotates) whereas an alternator has slip rings (no commutation/switching of current) on the armature. So while there are probably some uncrossable differences, some of those still could be muddied, especially if you get jiggy with the electronics processing of the output of whichever device is used (i.e, like replacing the brushes and commutator with electronics, etc.) We think of an alternator as having a field current that is teaked for regulation. A generator could have coils instead of permanent magnets for playing the same game. In that case, the commutation would be the only real difference - the rectification coming from the commutator (in a generator) up front of the actual power generation vs. in the diodes (alternator) after the fact. See what I mean about muddying the differences? *BUT*, to reiterate, it still is likely that the Prius uses what we traditionally think of as an alternator but is utilizing the retro-term "generator" in line with the trend in the automotive world. (BTW - since my previous post, I actually found a reference that said that the SAE, in 1993, started officially encouraging the dropping of the "misleading term alternator" and instead using the "proper term generator".) Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
From: Jeff on 7 Jul 2007 08:17 Elmo P. Shagnasty wrote: > In article <468EE014.7080507(a)hotmail.com>, > Jeff <kidsdoc2000(a)hotmail.com> wrote: > >>>>> With those electric motors there to help with low end grunt and getting >>>>> the car moving, the engine can be tuned more specifically for running at >>>>> certain efficient speeds. >>>> I always thought electric motors would make AWD very simple. >>> They do. Someone's doing that today. >> Who? Just curious. > > I've been trying to remember. I saw a mention of it in Car and Driver > magazine, I believe. It's been years since I read C&D. I would swear it was the original Escape design.
From: Jeff on 7 Jul 2007 08:34 Bonehenge (B A R R Y) wrote: > On Fri, 6 Jul 2007 20:26:21 -0500, "dh" <dh(a)stargate.com> wrote: > >> Aren't those giant dump trucks used in open pit mines electrically driven >> with a motor on each wheel? > > They are, as are mars rovers, battlebots, etc... Some are. But the biggest isn't. Here are the specs for the biggest Cat truck: http://www.cat.com/cda/layout?m=37840&x=7 Notice all the forward gears. I remember when C&D reviewed one. They talked about the steering: Does it understeer? Oversteer? Who knows? But the engine only develops 3400 HP and 12,000 lb-ft torque. <http://www.caranddriver.com/specialtyfiles/3629/specialty-file-caterpillar-797-page3.html> > Also. many locomotives and self-powered passenger cars (think subway > or commuter rail) use one motor per axle. Adding a differential to a > one motor per axle road vehicle doesn't seem that difficult. Or make it two motors per axle. Then you don't even need the axle (you get independent suspension).
From: Jeff on 7 Jul 2007 10:07 Bill Putney wrote: > Jeff wrote: >> Bill Putney wrote: >> >>> Jeff wrote: >>> >>>> Bill Putney wrote: >>>> >>>>> Jeff wrote: >>>>> >>>>>> Cars can also have electrically powered water pumps, power >>>>>> steering pumps, valves, and compressors for the air conditioners, >>>>>> although I don't know if any do, yet. >>>>> >>>>> >>>>> >>>>> An honest question: All those things suck energy whether >>>>> mechanically or electricaly powered (and the power has to >>>>> ultimately come from the IC engine). For each one, is the >>>>> electrical version inherently more efficient than a mechanically >>>>> powered (belt or gear driven) one? >>>> >>>> >>>> >>>> I think the electrically powered ones of these are usually more >>>> efficient, because they can be more efficiently shot off (even if >>>> you shut off the A/C, there still is loss from friction in the >>>> pulleys) and they operate at the proper speed (the A/C compressor in >>>> my car would run a lot fast if I drive in 3rd gear on the highway >>>> instead of 5th). >>> >>> >>> OK - makes sense. >>> >>>> Plus, I think the generating mechanism on a hybrid means less wasted >>>> energy. >>> >>> >>> Assuming you're not meaning strictly the regenerative braking, can >>> you explain what you mean? You're saying that the mechanism it uses >>> to convert mechanical energy into electrical energy is more efficient >>> than the alternator (the auto mfgrs. are back to calling them >>> generators now) in a traditional car? How is it done? >> >> >> A generator converts mechanical energy to DC current, not A/C current. > > Semantic technical point here: Yes - a generator converts mechanical > energy to electrical energy. It is only initial convention (before > portable alternators became practical with the development of compact > and efficient solid-state rectification means) that originally limited > the word generator to d.c. generating devices (basically from common > usage of the word in the context of the automobile). Well, the generator is A/C. I thought it would be D/C, but I was wrong. http://www.hybridsynergydrive.com/en/generator.html > Later, when the portable alternator was developed (or became practical - > and almost necessary due to the increasing current demands of cars), > just to distinguish the terminology, they came up with the term > "alternator" (which -yes - does suggest a.c. from a pure language > standpoint). However, there really is no reason the term generator - > from a pure language standpoint - could not mean alternator in that it > *generates* (i.e., no reason any device that generates *anything* could > not be referred to as a "generator"). > > NOW - having said that - one point I was making is that many of the auto > manufacturers have, within the last 5 or 10 years (not sure of the exact > time frame - they kind of snuck it in on us), in their documentation > (service manuals, etc.) gone back to the term "generator" to mean what > they had previously been calling (and you and I still call out of habit) > "alternators". And there's nothing wrong with that. If you look at an > alternator as a black box - ignoring what's inside - it turns mechanical > energy into d.c. voltage and current. So - hey call it a generator if > you want to. (And as I pointed out - even if it's final output *were* > a.c., from a pure language perspective, there would be no reason no to > call that too a generator.) > > Just wanted to get that fun point out of the way. > > Now - let's go a little further (and I'm not sure how this will tie in > to the discussion of hybrid cars) - what you and I know as alternators > pushed the "generator" (meaning d.c. generator) aside in the automotive > world because it (the alternator) was inherently more capable of high > current output across a much wider useable rpm range (i.e, the > traditional d.c. generator could not supply the increasing current > demands that cars were requiring in sustained low speed and stop and go > driving unless they were geared up to spin faster at low engine rpm to > the point that they would fly apart on the upper end of the rpm scale). > >> Because Toyota is so concerned with efficiency with the Prius, having >> an efficient generator system must have been a priority. And the >> output doesn't have to be converted to D/C with a rectifier. There's >> power loss in the rectifier. (All automotive alternators have them.) > > And perhaps there have been some technological developments that have > overcome the previous rpm range limitations of the (d.c.) generator. > Perhaps the engine is running at a more constant rpm with the drive > train used in the hybrid? I don't know. > >> Plus, the drive to the generators is direct drive, not belt drive >> driven, so there is less friction loss with a generator than a >> belt-drive. > > You may not have said that the way you intended to, but the way you > stated it, I don't buy that. There is nothing that says a (d.c.) > generator inherently has to be direct driven and that an alternator has > to be belt driven/cannot be direct driven. So unless I missed something > there, let's scratch that part of the explanation. When the belts go around the pulley, they flex. This results in some friction inside the belt. The pulleys are not friction free, either. This added friction, compared with direct drive, results in some power loss. By getting rid of the belts and pulleys, you decrease the friction, which increases efficiency. There is no reason why you can't have a DC generator or an A/C generator belt driven or direct drive. > In reality, I would not be surprised to find out that what they use and > call a "generator" is actually more like what you and I commonly refer > to as an alternator. I would also suggest that there is a bit of > electronic processing done on the raw output of the waveform that comes > out of this spinning device as to muddy the difference between what you > and I think of as generators and alternators and their traditional > differences such that we might have trouble deciding which category in > traditional terms whatever is in the Prius really fits into. In > addition, it would blend with the manufacturers tendency to now call > alternators generators anyway. When you convert A/C to DC or vice versa, there is energy loss (as heat in the diodes). This leads to lower efficiency. Apparently, Toyota got over this, because the generator is A/C, not DC. http://www.hybridsynergydrive.com/en/generator.html >> It is also inherently more efficient to drive these things from >> electricity than directly from belts, because they run at the proper >> speed, not a speed determined by the engine. Plus, you don't need to >> run the engine to run the A/C or other things, which saves on fuel >> (although you need to run the engine every now and then to recharge >> the batteries or otherwise recharge the batteries) and you can use >> regenerative braking to recharge the batteries. > > All true - I see those points. > >> SO there are a whole bunch of reasons why it is better to run these >> things off of electricity, not just one. > > Got it. > > Bill Putney > (To reply by e-mail, replace the last letter of the alphabet in my > address with the letter 'x')
From: philthy on 7 Jul 2007 10:17
if you want a real education on this look up the gmc truck hybrid that has been around since 02 the engine quits when it comes to a stop and the engine restarts when u pull away and u never know it i drove one and didn't know till i had to work on it after the test drive and was looking for some wiring Bill Putney wrote: > Bill Putney wrote: > > > ...In reality, I would not be surprised to find out that what they use and > > call a "generator" is actually more like what you and I commonly refer > > to as an alternator. I would also suggest that there is a bit of > > electronic processing done on the raw output of the waveform that comes > > out of this spinning device as to muddy the difference between what you > > and I think of as generators and alternators and their traditional > > differences such that we might have trouble deciding which category in > > traditional terms whatever is in the Prius really fits into. In > > addition, it would blend with the manufacturers tendency to now call > > alternators generators anyway. > > I should clarify here that there is an almost-unmuddiable aspect of the > alternators and generators (using the terms in the traditional pre-90's > automotive sense). That is that the generator will have a commutator > (to switch current in the windings as it rotates) whereas an alternator > has slip rings (no commutation/switching of current) on the armature. > So while there are probably some uncrossable differences, some of those > still could be muddied, especially if you get jiggy with the electronics > processing of the output of whichever device is used (i.e, like > replacing the brushes and commutator with electronics, etc.) > > We think of an alternator as having a field current that is teaked for > regulation. A generator could have coils instead of permanent magnets > for playing the same game. In that case, the commutation would be the > only real difference - the rectification coming from the commutator (in > a generator) up front of the actual power generation vs. in the diodes > (alternator) after the fact. See what I mean about muddying the > differences? > > *BUT*, to reiterate, it still is likely that the Prius uses what we > traditionally think of as an alternator but is utilizing the retro-term > "generator" in line with the trend in the automotive world. (BTW - > since my previous post, I actually found a reference that said that the > SAE, in 1993, started officially encouraging the dropping of the > "misleading term alternator" and instead using the "proper term generator".) > > Bill Putney > (To reply by e-mail, replace the last letter of the alphabet in my > address with the letter 'x') |