[MooseFET]

Nobody [email protected] posted to sci.electronics.design:







NO! The electric drive train has to be sized to the maximum
(majority electrical contribution) acceleration in all cases. It
must be sized (possibly much) larger than the ICE.

Toyota seems to agree that the dual electrical machine design needs
less hardware to get the job done. I think this is because the
electricals only need to provide the acceleration at low speeds. This
reduces the peak power that must be delivered by the electrical
system.

 

[MooseFET]

Energy = force * distance. Drag force is proportional to speed squared, so
energy per unit distance is proportional to speed squared.

Yes you are right. It was a short circuit between the headphones. I
saw "drag" and somehow read "horse power".

 

[Guy Macon]

Toyota seems to agree that the dual electrical machine design needs
less hardware to get the job done. I think this is because the
electricals only need to provide the acceleration at low speeds. This
reduces the peak power that must be delivered by the electrical
system.

Toyota choose the electrical / internal combustion switchable
design, but it has not been established that they did so
because that design needs less hardware to get the job done.
It could be that that design is easy to build on existing
assembly lines, or because of some other reason.

Nobody has yet produced a car using the locomotive topology; an IC
engine driving an electric generator whose output provides power
to traction motors with no mechanical connection between the ICE
and the wheels -- in essense an electric car that incorporates
its own generating station. There are persistant rumors that the
upcoming Subaru system will use this scheme. We know that such a
system can be made to be very fuel efficient indeed in a locomotive;
the question is whether this advanage will remain in an automobile.
One difference would be that the automobile will likely have
batteries to even out the load between accellerating and coasting.

A locomotive-style auto would have some interesting characteristics;
at all but the very slowest speed it outputs close to constant power,
so the torgue at the driving wheels will tend to inversely vary with
speed. A motor-per-wheel system with the proper electronic control
would be easy to configure with traction control, anti-lock baraking,
and regenerative braking.

 

[Eeyore]

On the highway, the engine gets connected directly to the wheels.
This takes the sosses of the electric machines out of the picture.

What losses ? Electric motors are highly efficient.

It also allows the engine and both motors to be used for passing power.

At the cost and complexity of requiring a transmission. I just don't see any sense in it.

Graham

 

[Nobody]

At the cost of a vastly more complicated drive train.

But they have decades of experience of making those, along with the
designs, the tooling, the network of maintenance garages and spare parts
for when the mechanics wear out. I suspect that a large proportion of the
mechanical drivetrain is taken from a similar pure-ICE vehicle.

With a plug-in hybrid you may not even need to use the ICE/generator on shorter journeys.
Hence no additional losses at all.

If that's the normal case, then it's debatable whether it's worth
including the ICE/generator at all. If it isn't the normal case, then the
efficiency is significant.

Motorway cruising does not require high power. It's acceleration that requires high power.
You can cruise at motorway speeds with say 30kW.

It's cruising that requires the power. Acceleration requires the
most torque, but not necessarily the power. Also, cruising requires that
power continuously, whereas acceleration only requires it intermittently.
There's a difference between sizing a motor for 30kW continuous power and
for 30kW bursts (especially regarding cooling).

Personally, I feel that the series hybrid can be made viable, but it's
going to take time and effort. So far, research into electric vehicles has
been a drop in the ocean compared to that on ICEs. OTOH, by the time that
the output side (motor, power electronics) has matured, the landscape on
the generation side may have changed considerably (e.g. fuel cells).

 

[Nobody]

What losses ? Electric motors are highly efficient.

Any motor inefficiencies are doubled (the generator likely has similar
losses to the motor), and added to any losses in the power electronics
(which may increase when running at full power continuously; e.g.
a MOSFET's R[DS(on)] increases with temperature).

At the cost and complexity of requiring a transmission. I just don't see any sense in it.

Mechanical transmission is what they're familiar with. Current hybrids
largely try to tweak existing technology rather than starting with a
clean slate.

 

[Nobody]

I drove a Peugeot 1.9 turbo diesel as long ago as 1988. It was pretty brisk. Performance seem to
be less of an issue with diesels these days although they don't rev as fast.

They do take a bit of getting used to. If you're used to petrol, it takes
quite a while to get into the habit of changing up earlier (when your
subconscious is convinced that the engine would splutter).

 

[default]

"default"



** The Roadster has a recharge time ( from dead flat ) of 3.5 hours -
according to the makers.

Only thing is, owners need to have a dedicated, 3 phase power outlet
available at home with a capacity of 15 kW - then it will costs about
$10 or so in electricity for a full recharge.


However ..............

- just load the boot (ie trunk in the USA) with a bunch of these babies
and get it done in only 1 minute !!!!!

http://www.dcviews.com/press/Toshiba-One-minute.htm


All you need is ** 3 megawatts ** capacity in the garage !!!!!

Circa 4500 amps per phase .




....... Phil

Most of us don't have three phase outlets and it is expensive to get.
The twelve hours is from a source you'd have at home. Cross country
would be a problem - long extension cords and very accommodating motel
owners.

One alternative to a different class of electrical service might be
super caps or storage batteries that could sip electricity all day
long then pass it to the car in one big gulp.

 

[Eeyore]

What losses ? Electric motors are highly efficient.

Any motor inefficiencies are doubled (the generator likely has similar
losses to the motor), and added to any losses in the power electronics
(which may increase when running at full power continuously; e.g.
a MOSFET's R[DS(on)] increases with temperature).

It seems to just argued against using any electric motors at all.

Mechanical transmission is what they're familiar with. Current hybrids
largely try to tweak existing technology rather than starting with a
clean slate.

Which is why the advantage they offer is so poor.

Do wake up.

Graham

 

[Eeyore]

They do take a bit of getting used to. If you're used to petrol, it takes
quite a while to get into the habit of changing up earlier (when your
subconscious is convinced that the engine would splutter).

It took no 'getting used to' at all.

Graham

 

[Eeyore]

They do take a bit of getting used to. If you're used to petrol, it takes
quite a while to get into the habit of changing up earlier (when your
subconscious is convinced that the engine would splutter).

And modern engines don't splutter !

 

[Eeyore]

One alternative to a different class of electrical service might be
super caps

Have you any idea how poor the energy density of even super caps is compared to
batteries ?

Graham

 

[default]

Have you any idea how poor the energy density of even super caps is compared to
batteries ?

Graham

No. The point I was making was the idea of an interim storage system
just to bypass the need for three phase power or super high amperage
service, long runs of high current wire etc.

Vacuum flywheel?

No reason to expect practical solutions yet - new technology takes
time and demand, practical takes time.

I don't think the Tesla Roadster is practical, but I'm glad it is
there. Now what about my diesel hybrid motorcycle?

 

[Nobody]

On the highway, the engine gets connected directly to the wheels.
This takes the sosses of the electric machines out of the picture.

What losses ? Electric motors are highly efficient.

Any motor inefficiencies are doubled (the generator likely has similar
losses to the motor), and added to any losses in the power electronics
(which may increase when running at full power continuously; e.g.
a MOSFET's R[DS(on)] increases with temperature).

It seems to just argued against using any electric motors at all.

Not at all. Motors are a lot more efficient than an ICE. But if you're
using an ICE as the power source, you're not comparing motor efficiency
against ICE efficiency, but an electric generator->conversion->motor
drivetrain against a mechanical drivetrain.

It may still win, either in absolute or relative terms (i.e. whether or
not you take into account the ability to run the ICE at optimum
speed/load). But for now, the issue is whether it wins by enough to
overcome the inertia of sticking with the "safe" option.

Which is why the advantage they offer is so poor.

Do wake up.

You seem to be looking at it from an "ideal world" perspective, i.e.
considering the technology on its merits alone.

I don't think that's a particularly meaningful perspective. None of the
major car makers are going to abandon ICE technology soon, so they will be
looking to "dual-purpose" as much of their existing technology and
infrastructure as possible.

If you design an engine purely for a serial hybrid, the result isn't going
to look anything like a normal car engine. The same applies to much of the
rest of the car: wheels designed for embedded motors won't look like those
designed for an axle. Cooling for an engine whose power doesn't vary with
speed is a different problem than for one which relies upon forward
motion for the airflow. And so on.

A ground-up redesign involves a lot of cost and a lot of risk. Even if
it's successful, you end up competing with yourself, as gains in one
technology don't easily transfer to the other.

I just don't see any major car maker betting their future on electric
vehicles right now. Development will be incremental, and entirely
subordinate to the constraints of their conventional production lines.

 

[Eeyore]

On the highway, the engine gets connected directly to the wheels.
This takes the sosses of the electric machines out of the picture.

What losses ? Electric motors are highly efficient.

Any motor inefficiencies are doubled (the generator likely has similar
losses to the motor), and added to any losses in the power electronics
(which may increase when running at full power continuously; e.g.
a MOSFET's R[DS(on)] increases with temperature).

It seems to just argued against using any electric motors at all.

Not at all. Motors are a lot more efficient than an ICE. But if you're
using an ICE as the power source, you're not comparing motor efficiency
against ICE efficiency, but an electric generator->conversion->motor
drivetrain against a mechanical drivetrain.

And if the ICE is operating in its most efficient regime in its generator application (which it
will be) all those losses will still outperform an ICE driving the wheels directly.

Plus, pure electric traction easily lends itself to the most effective and easily implemented
regenerative braking, and traction control etc etc..

Graham

 

[Eeyore]

None of the major car makers are going to abandon ICE technology soon, so they will be
looking to "dual-purpose" as much of their existing technology and infrastructure as possible.

V8 hybrids ? Don't be so ridiculous.

If US auto makers don't change their ways soon, they'll be out of business.

Graham

 

[Eeyore]

If you design an engine purely for a serial hybrid, the result isn't going
to look anything like a normal car engine. The same applies to much of the
rest of the car: wheels designed for embedded motors won't look like those
designed for an axle.

That's exactly the point. A series hybrid probably only needs about a 500cc engine.

Graham

 

[Mark]

It seems to just argued against using any electric motors at all.

Yep, I think the small batteries and electric motor in the Prius are
there for only 2 reasons..

1) efficency gained by regenerative braking
2) improve the acceleration so the ICE can be smaller also improving
the efficency.

If you had the small ICE without the acceleration boost provided by
the electrics, the acceleration would be poor and people would not
like the "drivablility".

Intersting to note that a flywheel could provide the same advantage.

In fact I tend to think of the battery and electric motor in the Prius
is just an electric implementation of a flywheel.

Mark





Mark

 

[Nobody]

Intersting to note that a flywheel could provide the same advantage.

In fact I tend to think of the battery and electric motor in the Prius
is just an electric implementation of a flywheel.

There has been research on using flywheels, primarily for buses. The
problem is that you need a (relatively high-torque) variomatic
transmission to avoid shearing the gears and/or incinerating the clutch.

With the electric approach, the variomatic transmission is achieved
through PWM, which seems to be better understood than the mechanical
equivalent.

 

[Glenn Gundlach]

advantage.

There has been research on using flywheels, primarily for buses. The
problem is that you need a (relatively high-torque) variomatic
transmission to avoid shearing the gears and/or incinerating the clutch.

With the electric approach, the variomatic transmission is achieved
through PWM, which seems to be better understood than the mechanical
equivalent.

Also the issues with gyroscopic precession.

Less than good here

http://blogs.edmunds.com/Straightline/2257

Interesting here

http://www.cleangreencar.co.nz/page/prius-petrol-engine

GG