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Discussion Starter #1
I swear I read that after the battery runs out the car uses an engine to generate electricy for the motors. And it gets 50 MPG doing this. How can this be true? If it can get 50 MPG by generating electricy then why don't other small cars use electricy generated by a motor to get 50 MPG? What am I missing here?
 

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Below is what I posted to a similar question on the Home threads, hope this helps:

Because the engine needs to be made for relatively low power delivery and gradual changes in power output to achieve 50mpg. This would not result in acceptable performance. A powerful battery or other power source is needed for peak power demands in order to have acceptable performance. Once this “large” power source is added, the additional for enough storage to achieve 40 miles AER is not that great.

GM is by no means beyond reproach, but they have made a VERY, VERY, VERY good choice in developing EFLEX EREVs. The Volt is the first iteration of this drivetrain. In allnlikelihood, it will be improved and implemented accross all of their brands and many other platforms. One of the few iterations they have mentioned is a 20 mile AER version. This will probably be the first “affordable” EREV solution, but if batteries alone continue as the eletrical storage technology of choice then I doubt we’ll see less than a 20 mile EREV anytime soon.
 

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Like Koz said, you need the battery as a buffer to get the engine that efficient. The engine can run at its most efficient rate all the time that way.
 

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regen

you also get the benefits of regenerative breaking when you use a series hybrid this way. recovering power that would otherwise be wasted without a battery.
 

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I think the

main difference is that he GM version charges the batteries, and does not drive he car, therefore it can be set to optimum RPM for efficiency. Other hybrids use the ICE to drive the car, and an electric assist. The Volt is electric drive with ICE assist. Other hybrids do not have a disconnect from the ICE to the drive wheels.

This lack of requirement to vary the engine rpm improves the efficiency as the motor can possibly be simply idling at cruising speed if there is sufficent charge being prduced. Imagine driving 55mph with a 1.4 liter engine idling!!!

That is the beauty and difference that is VOLT!:D
 

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A more detailed answer

“I read that after the battery runs out the car uses an engine to generate electricity for the motors. And it gets 50 MPG doing this. How can this be true? If it can get 50 MPG by generating electricity then why don't other small cars use electricity generated by a motor to get 50 MPG? What am I missing here?”

Or to put it more succinctly:
So how can a Series Hybrid get much better mileage if it still uses an old-fashioned internal combustion engine to generate electricity?

The Answer lies in the difference between the *average* power draw of a vehicle, and the *burst* power requirement that is the standard for determining vehicle performance.

First, THE BACKGROUND:
A standard internal combustion engine (ICE) vehicle is sized for its *maximum* power production -- think of top-end hp and torque numbers. Those top numbers represent the "oomph" the car depends on for those brief seconds of maximum (or ‘burst’ torque) acceleration. Carmakers are aware that customers want to have a car that is fast off the mark for merging into highway traffic and other situations, and are wary of downsizing the engine and making a car's performance anemic despite efficiency gains from a smaller and lighter engine. They’ve learned this painfully from the hostile reviews to very inexpensive, and underpowered cars like some of the old (and >40mpg) Honda Civics, or the Geo Metro. Therefore standard ICE vehicle engines have to be made for that "burst" requirement.

If a typical sedan requires perhaps 25-35 kW of power, but in order to gain market acceptance it needs to apply 4-6 times that power (150kW or more) for a several seconds at a time, then the ICE has to be over-engineered, heavier, and more expensive. Additional efficiency is lost since every ICE has a particular speed where it is most efficient, and this overpowered engine is constantly shifting its rpm which occasionally takes it out of that maximum efficiency zone, which results in poorer gas mileage.

Second, THE FACTS:
From a mileage perspective, a *small* gasoline or diesel motor can give superb performance , as long as excess energy for that ‘burst’ requirement is stored in a battery or capacitor. A Series Hybrid, like the Volt, ICE motor would be optimized and tuned for a limited speed and power range, which gives better efficiency (and lower emissions) than today’s automotive engines that must operate from 500 to 5000 rpm. Therefore a smaller motor, sized like the 50-60hp of a Geo Metro, would easily generate 40+ mpg, yet still throw a medium or large car around with impunity either using the ‘burst’ torque from either over-sizing the 3-Phase AC induction electric motors on the Volt, OR using a multiphase AC induction motor/drive such as Chorus Meshcon. However, The Chorus Meshcon inverter/drive is presently found only in aerospace at the moment (Wheeltug.com/ChorusMotors.com).

Since the alternative, Chorus Meshcon, can provide TEN TIMES the ‘burst’ torque of any conventionally sized and hp rated motor, a Volt using this motor wouldn’t need to oversize the electric motors as they do now and the volt would further gain from the weight savings. And since the power draw during those rare 10-15 seconds of (up to) 10x ‘burst’ torque can come from a capacitor bank or an ultracapacitor, the number of batteries can be reduced as the batteries would not need to be configured to provide that much short term power (which would come from capacitors.)

Also, Chorus Meshcon Motor/Drive is particularly good at low speed-high torque operations, which is why Delta Airlines will be installing it (in the ‘Wheeltug’ configuration) on their fleet of 737NGs in 2010 (after FAA certification is completed in 2009) to drive their planes forwards and backwards without the use of tugs or the planes own engines: that’s a lot of torque for an electric motor that will fit within the hub of the planes nosewheel. I would expect that if the Volt incorporated Chorus Meshcon, the power train gearing of the vehicle would be simpler as well since Chorus Meshcon can operate both as a low speed-high torque motor and high speed motor.

The Series Hybrid car approach of the Volt is fundamentally correct in terms of the power train; using a small ICE to gain fuel efficiency by operating at a single peak efficiency speed. In comparison, insisting on the "plug-in" approach that requires batteries that do not exist (and if they did would not be affordable) represents numerous limitations, including infrastructure changes and recharge time, plus those additional batteries add hundreds of pounds of extra weight. GM admits that the Volt is likely to top a sticker price of $45k -- and a lot of that is the battery.

I really think that the Volt would experience a radical price drop if it used the Multi-Phase Chorus Motor instead of the historical standard 3-phase AC Electric Motor since a Chorus Meshcon Inverter/Drive would be smaller and sized more directly to the ‘average’ power draw for the motors while providing the exact ‘burst’ torque that is needed for those rare 10-15 seconds when you have to go from a stop to merging onto the highway. At present the ‘over-powering’ of the ICE in a standard vehicle (causing mileage inefficiency) has been transferred slightly to the Volt by over-sizing the 3-Phase AC electric motors. Again, mileage is being lost by having to use a motor that is more powerful than needed, by designing it for the occasional ‘burst’ requirements. The next step is to go with a motor that can do this at a 10x ‘burst’ torque without having to change the size/weight of the motor to be anything other than what you need for the ‘average’ power draw, and that step can only be Chorus Meshcon. They even have a site with information on how their motor can be applied to Series Hybrids (ChorusCars.com) and outperform on both price and performance either Permanent Magnet or 3-Phase AC Induction electric motors on both PRICE and PERFORMANCE.
 

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regen power

A PM (Permanent Magnet) motor can provide regenerative power.

In a PM, whenever there is movement in relation to the magnets, you have electron flow, which is both a blessing and problem.

An AC induction motor, whether 3-phase or Multi-Phase (12 ,18, or higher) would be the same when it comes to regenerative power.

You can find out more from contacting www.ChorusMotors.com
 

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Can you please elaborate on

An AC induction motor, whether 3-phase or Multi-Phase (12 ,18, or higher) would be the same when it comes to regenerative power.

Are you saying the Chorus solution has the same problem as PMs or as other AC motors?
 

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answers

"Can you please elaborate on

An AC induction motor, whether 3-phase or Multi-Phase (12 ,18, or higher) would be the same when it comes to regenerative power.

Are you saying the Chorus solution has the same problem as PMs or as other AC motors?
"​

PM motors can do regenerative braking because current is generated (due to there being permanent magnets) whenever the wheel spins freely. AC induction motors can’t do regenerative braking like a PM motor.

I’m not sure what problem you are talking about since both PM motors and AC motors have ‘different’ problems which make them a critical decision in the development path of a hybrid. In the Volts case, the early decision was to go in the ‘other’ direction from the Prius, which has a PM motor (which fails at high temperatures and requires liquid cooling, adding weight, complexity, and cost). I’m glad that GM went with an induction motor which can be air cooled, even though it was at a tradeoff.

In this case, the Volt has a 3-Phase AC induction motor which requires a ‘larger’ motor than the equivalent powered PM motor. It also needs to be larger for that ‘burst’ torque I mentioned earlier even though that burst torque is rarely needed. By over designing the electric motors (like they do on a standard ICE vehicle) you are getting less mileage than you might otherwise get.

Chorus Meshcon has none of the drawbacks of PM’s (failing at high temperatures, requiring rare earths, etc.) and none of the draw backs of an AC (low-speed/high-torque problems, require larger motor for ‘burst’ requirements.). It simply is a new motor that goes beyond the first three phases that a 3-Phase AC Induction motor uses, and is the first to do it successfully. The company that designed it has found the ‘ideal’ application for it by applying it to the aerospace industry and saving them close to 20lbs of fuel per minute that the planes burn while taxing, and all in a 100lb package to move a 737.

I just hope that they can get the Volt engineers to look at Chorus Meshcon before those same engineers ride on the 737’s with Chorus Meshcon installed on the planes nosewheel. It simply seems like the perfect ‘improvement’ that will provide better mileage and a longer range for the Volt.
 

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A PM (Permanent Magnet) motor can provide regenerative power.

In a PM, whenever there is movement in relation to the magnets, you have electron flow, which is both a blessing and problem.
Not exactly true. There must be a closed-loop circuit in order for the current to flow.
 

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Closed loop faults in PM motors happen. Akin to an arc welder....

I would call that a problem, especially with fuel & passengers near by.

Such faults can occur when motor windings overheat, if the magnets haven't degraded first.

AC motors fail to open circuit.

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Aaron, I extracted the word 'problem' from your #2 post looking for elaboration,
In a PM, whenever there is movement in relation to the magnets, you have electron flow, which is both a blessing and problem.

Very little has changed in basic motor design for many decades. Looks like Chorus might shake that up some what. Lighter / denser / cheaper / safer.
 

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Elaborate

It's not the 'same' problem. They have different weaknesses and strengths.

PM motors fail at higher temperatures and need a cooling solution. The Volt avoids that added complexity with a 3-phase AC electric motor. And PM motors perform better at low speed-high torque applications.

The Multi-phase Chorus Motor is able to provide the extra torque even at low speeds, and can literally have a ‘Virtual Transmission’ for shifting between high speed and low speed operation such that you don’t need complex and/or heavy gearing. It is literally the best of both worlds, without the respective weaknesses of both PM and 3-phase AC electric motors.

A Volt with Chorus Meshcon could probably have smaller electric motors because they would be able to deliver 10x the torque on those rare occasions, and that extra torque wouldn’t need to be built into the electric motors by ‘oversizing’ them as is likely the case at present. You just get more ‘burst’ torque out of a Chorus Meshcon inverter/drive without needing a complex solution for cooling it or dealing with the current that comes from having a permanent fixed magnet motor.
 

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“PM motors fail at higher temperatures and need a cooling solution… ” – Aaron Bianco

??? Are you talking about the Curie temperature? If so, it is about 590 degrees F (310C) for neodymium variety of magnets (much higher for samarium-cobalt type). Before you reach this temperature the motor itself will fry. I do not think the Prius motor is force-cooled either by water or air.

“The Volt avoids that added complexity with a 3-phase AC electric motor… ” – Aaron Bianco

Although I could not find information as to what kind of motor the Volt will be using, I think it will be a kind of permanent magnet synchronous motor, since this type of motor can be switched easily to a generator (for energy regeneration). Unless the ICE-driven generator is also mechanically connected to a wheel, it would be more practical to trun the drive motor into a generator when braking and coasting. The Chorus Meshcon motor is essentially a VVVF (variable voltage, variable frequency) controlled AC induction motor. Nothing special. Modern electric trains all use the VVVF system.

“… or dealing with the current that comes from having a permanent fixed magnet motor… ” – Aaron Bianco

To deal with the counter-electromotive force generated by the permanent magnet motor you do either of the following:

1) keep increasing supply voltage above the self-generated voltage
2) weaken (in effect) the generator magnetism
3) keep the motor speed low (in-wheel motors help since their max speed is around 800 – 1000rpm)
 

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Answer to G35X

“PM motors fail at higher temperatures and need a cooling solution… ” – Aaron Bianco

??? Are you talking about the Curie temperature? If so, it is about 590 degrees F (310C) for neodymium variety of magnets (much higher for samarium-cobalt type). Before you reach this temperature the motor itself will fry. I do not think the Prius motor is force-cooled either by water or air.
I'm looking up that information now. I know that there is a critical performance drop for the Prius, which is why they went with liquid cooling instead of the Air Cooling that would be required for an standard 3-phase AC induction motor or with a Multi-phase (more than 3 phases) AC induction motor like the Chorus Motor.

“The Volt avoids that added complexity with a 3-phase AC electric motor… ” – Aaron Bianco

Although I could not find information as to what kind of motor the Volt will be using, I think it will be a kind of permanent magnet synchronous motor, since this type of motor can be switched easily to a generator (for energy regeneration). Unless the ICE-driven generator is also mechanically connected to a wheel, it would be more practical to trun the drive motor into a generator when braking and coasting. The Chorus Meshcon motor is essentially a VVVF (variable voltage, variable frequency) controlled AC induction motor. Nothing special. Modern electric trains all use the VVVF system.
You can find it at autobloggreen.

The Prius uses a PM motor, and the Volt will be using a 3-Phase AC induction motor. At this time, there have been no announcements regarding using "Multi-Phase" AC induction motors in the transportation industry other than in Aerospace applications (see Delta Airlines) where Delta will be using Chorus Meschon on 'Wheeltugs' so that their fleet of Boeing 737NGs can drive themselves around with their engines off.

“… or dealing with the current that comes from having a permanent fixed magnet motor… ” – Aaron Bianco

To deal with the counter-electromotive force generated by the permanent magnet motor you do either of the following:

1) keep increasing supply voltage above the self-generated voltage
2) weaken (in effect) the generator magnetism
3) keep the motor speed low (in-wheel motors help since their max speed is around 800 – 1000rpm)
All good techniques, and all require some 'additional' engineering, which adds to the cost/weight. These additional complexities/costs can be shaved off by switching to a 3-Phase AC induction motor, but that only shifts to 'different' complexities/costs as 3-phase AC induction motors have other issues that need to be dealt with on an engineering level.

There is only one other motor option that has a unique set of characteristics that 'solves' the need for the 'engineering' solutions, and that is the Chorus Motor, but at present it isn't being used in Automotive industry but it is being implemented in the Aerospace industry and is undergoing FAA certification at them moment. The topics regarding these complexities/costs that come from the two main types of electric motors (PM & 3-phase AC) are addressed at www.ChorusCars.com
 

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The Chorus Meshcon motor is essentially a VVVF (variable voltage, variable frequency) controlled AC induction motor. Nothing special. Modern electric trains all use the VVVF system.
You are correct that VVVF systems have been commonly available in motors for years. But that is like saying that words on a page have been around for millenia, so Hamlet is nothing special. :)

I think the question is a simpler one: does Chorus do something that other VVVF motors do not, and if so, is it a technological and/or commercial advantage that should be used in hybrid vehicles?

If the claims of much higher peak torques are correct, then it would appear that Chorus might have something?
 

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Peak torque

It does have higher peak torque, this is one of the reasons Delta wants it on their planes, to back them out of the gate (from a dead stop) AND to run them around on the tarmac.

And Chorus does do things that VVVF motor cannot do, and if implemented in a Series Hybrid, it will help achieve the 50mpg+ that "KansasGuy" was doubtful about in his first post, due to reducing complexity and providing tremendous 'burst torque' from a small package.

And I'm awaiting some information regarding PM motors suffering performance problems to answer G35X's question. I should have bookmarked the info, but I didn't.
 

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http://www.osti.gov/bridge/product.biblio.jsp?osti_id=885987

Looks like the Prius cuts out ENTIRELY at 170C, and is weakened at lower temperatures. Presumably Toyota knows what they are doing, so these thermal limits are there for a reason.

As the Oak Ridge report says, the Prius motor is entirely unsuitable as a sole drive motor because of thermal limits. So this part of the Chorus story seems to check out.
 

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beat me to it

Thanks, you beat me to it. :)

Chorus Motors has definitely done their research on PM & (3-phase) AC electric motors. They've come to the firm conclusion that thier motor is a perfect fit for Series Hybrids in that they overcome the individual problems inherent to each motor with regards to Series Hybrids (www.ChorusCars.com). And the 'burst' torque (weight savings as a result) will be instrumental to getting the gase mileage up as per my previous post on the topic in response to Kansasguy
 
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