My point would have been better made by pointing out that what comes from the MG's during regen is multi-phase AC of varying voltage and frequency and therefore would not typically be directly used to run the compressor.

 

"...The AC does increase drag.."

Not just drag but sudden "jerks", "SURGE" loading, of the belt due to the on/off nature of the compressor clutch and the need to start the compressor turning against a pressure "head".

 

Of course you are correct. Does the FEH have a generator (one that produces pure DC power straight from the brushes)? I suspect not.

Normal cars charge their batteries and power their lights with an alternator which also outputs "multi-phase AC of varying voltage and frequency", but that power is rectified and regulated to make it suitable for use in a 12VDC system.

We are arguing semantics. I never intended to imply the the 2010 FEH's electric AC (Air Conditioner) drew AC (Alternating Current) directly from the MGs before conditioning.

If you have ever had circuit theory you would know that even if you could trace wires directly from the Air Conditioner to the battery the power could still be coming from another source, depending on the battery voltage and the system voltage. If the system voltage exceeds the battery voltage the battery is consuming power, not outputting power.

 

Stevedebi:

You're right, electric driven compressors have been around for many years. My point was that to do so with a 12vdc motor would require a physically large motor for the power needed. The starter motor (of a conventional car) is quite powerful and small, but remember it is not rated for continuous running.

However, if you use a HVDC motor powered from the traction battery circuit, as the power steering motor is powered, then the motor gets physically much smaller. A smaller motor could fit nicely into the engine compartment and simplify the A/C and engine control.

This required some rethinking by Ford. I believe also that greater confidence in the traction battery and associated circuitry played a part. You're also right about the incremental approach on things like this.

That sort of plays to my point about power steering, Ford had to face it from the beginning. With A/C they could use an off the shelf system and come back in a few years (remember this engine design already had a serpentine belt system in place). In any event, we can't get into the brains of their designers, we can only speculate.

The talk of free power for A/C is a side issue. A/C requires several horsepower that don't come for free. The only "free" thing on an ICE is winter time heat.

Regarding serpentine belts wearing out... my one data point is my Suburban. I have replaced its serpentine belt 8 times in 384k miles. Every one was a failure caused by something else like an alternator seizing, a power steering pump seal failure that soaked the belt with oil, and an idler bearing that seized shredding the belt.

In my observation wear on the belt is a side issue discussion. It will be replaced by mere age if not damage from some other component. The beauty of the serpentine belt system (I treat it as a separate system on my cars after the Suburban experience...) is that it has the tensioning pulley. If you keep things aligned it could go forever if it didn't age.

 

Just to be clear:
MG 1 & 2 are AC Synchronous machines. Their frequency is directly proportional to shaft RPM. In the case of MG1 it is geared to the wheels and so its frequency is directly proportional to speed. MG2 is a function of the planetary gear set causing its rotation & stimulating AC frequency.

The controller or inverter assembly is designed to receive 3 phase AC from MG1 or 2 and send rectified 3 phase AC to the battery for charging.

The controller for the transaxle controls the ICE as an independent power input to the gears (or power absorber in negative split mode). Depending on the torque demanded it sends an AC frequency to MG 1 or 2 (independently) to increase speed or generate electrical current.

The controller also selects the appropriate voltage to cause MG 1 or 2 to generate power or drive the wheels. Since MG1 & 2 are permanent magnet rotors the output voltage is only proportional to rpm. Remember that the rotor will always be in precise synchronism with the rotational rate of the 3 phase AC sent by the controller.

In essence if the voltage supplied to MG 1 or 2 is above that resultant from rpm it will function as a motor (net current flow into the machine). If the voltage supplied is below that from rpm it will generate electrical power (net current flow out of the machine).

The transaxle controller has a lot to do. Hence programming is absolutely critical. I believe Ford did a nice job on this programming.

The use of "multi-phase" AC is technically a misnomer. Though in strict English it conveys the thought, standard engineering parlance would simply call it 3 phase AC. There is no purpose in having more phases than 3 for power units.

The unit that functions as the alternator in a conventional car is the dc-dc convertor which takes in HVDC from the traction battery circuitry and produces the needed 12 vdc for the rest of the car.

 

Someone correct me if this is wrong but I have understood the FEH's electric power stearing to be the standard industry wide off-the-shelf 12 volt system.

So, instead of saying the A/C is run by at least a portion of the "free" energy recovered via regen shall we use the term "regen energy" rather than "free"...?? Would that be more acceptable by all..??

" The only "free" thing on the ICE is winter time heat.."

So, you're saying that "recovery" and use of the heat originally generated by the burning of fossil fuels but might otherwise be wasted, as in summertime, consititutes "free", but electric current recovery via regen is not "free".

Interesting, VERY interesting.

 

Multi-phase as a misnomer...

I was thinking of the possibility of two or three phase when I wrote that since I have no "evidence" that the FEH uses whichever and 2 phase would undoubtedly by less expensive to implement an would work just as well.

With the advent of the inexpensive, ready availability, of the 2-phase solid state technogical brushless motor drives many modern day synchronous motors, and even induction motors are being used throughout the industry, including automotive.

 

A heater in an electric car would also require several horsepower but in an ICE driven car there is excess waste heat so you are calling winter time heat in a ICE powered car "free". One could argue that in a hybrid the recovered energy that would have been lost to friction brakes is also "free". The only difference I can see is that in the case of free heat you only have 2 choices, heat the car, or waste the heat. With a hybrid the "free" energy goes into a battery and you can use that energy for any electric device, from the traction motor(s), to your iPod, including electric AC. Having so many choices complicates the discussion.

I'm backtracking a little to meet WW halfway. Certainly we can all agree that if you spend your "free" energy budget on AC it will not be available for other things?

You have just made my point regarding belts. Using your example, belts last about 50k miles. Would these failures by other things have caused secondary failures if the vehicle was beltless, like the 2010 Prius?

For example: The idler bearing...With no belt to shred there is no need for the idler in the first place so that never would have happened in a beltless system.

If your PS had been electric and a seal leaked it would have spilled oil on the ground with no consequence, even if it spilled on the wires it is likely no damage (other than to the PS unit itself) would have occurred. Even if the electric PS unit locked up completely all that would have likely happened is a blown electric PS fuse. Advantage electric, for sure IMHO.

If, if...?? Seriously? We live in the real world and to put it mildly "stuff" happens. I don't really care what causes a belt to fail, I only care that the belt has failed rendering a vehicle (or machine) unusable.

BTW I've got decades of experience working on electromechanical things and belts are one of my biggest headaches. Electric stuff tends to last a long time, unless a stinking belt gets tangled up in the wires!

 

Hey, hey big tuna... it'll take you awhile... but meeting ww halfway is a bad idea.

...And your logic is sounding only partially vast... no energy is free (except waste heat that you haven't figured out how to use). "In the world of energy & thermodynamics, you can't even break even." (Dr. Isaac Asimov, 1971)

You know... energy re-captured by regenerative braking isn't free... you already bought & burned the gas to make it. You just didn't lose as much of it as if you hadn't re-captured it. ...And don't forget the cost of the unique recovery systems.

With your experience in electro-mechanical things and what sounds like a lot of belt failures... try aligning the pulleys. The belts'll last longer.

Listing a shredded belt as a belt failure when the cause was a seized alternator bearing, shows a fundamental lack of understanding of engineering. You can do better.

You know, when that PS Pump failed and oil soaked the serpentine belt, I could have left it in. It looked OK and probably would have gone another 10k and maybe a good bit more, but, you know, why spar with the big guy?

My experience with that Suburban (at 384k now) has enabled me to do predictive maintenance. For example the alternator fails right about 85k. It appears to be a heat thing from air flow inside the engine compartment. One of its bearings fails, the front one.

So now I just replace it before it goes, but I don't replace the serpentine belt. I'm now at 80k+ on this belt and its going strong.

BTW I learned to treat the serpentine belt system as if it were a separate component from my Suburban experience. The idler & tensioner bearings need to be replaced periodically so they don't fail on the road.

I've chosen 150k as the interval for replacing these bearings. That's just a start, I'll have to watch the Suburban for another 100k or so to get a better idea what the interval should be, but I won't drive to failure this time.

And yeah, I did replace the belt tensioner bearing and both idler bearings on my Mustang (4.6 L DOHC) once I concluded the serpentine belt system was a separate component. It was at 252k when I did that and yeah, it was the OEM serpentine belt that I left in place.

 

Thanks for the advice.

By this logic even your "free" heat isn't free, since fuel was burned to make the heat.

I didn't actually do that if you go back and look. I mentioned the idler and the PS pump, not the alternator. In the case of the alternator the belt may have been beneficial by acting like a mechanical fuse. Someday I expect belt drive alternators to be replaced with motor driven alternators anyhow...jk



We have had several compressors over the years. At one building they have a belt drive and yes it generally works fine. It has ganged belts to distribute the load. If the pulleys are aligned the belts last a while but even with the correct alignment they still eventually wear out. If the pulleys become misaligned in any direction the belts wear out in no time. The shafts must be perfectly parallel or one belt will be loose and one will be tight.

At another building we have a direct drive compressor. The motor has a direct mechanical link to the air pump. This compressor is practically maintenance free. There are no belts to wear out and no pulleys to align. You gotta monkey with oil and that is about it.

You are clearly a very intelligent and knowledgeable person (my guess is you are an engineer), which system sound better to you (keeping in mind maintenance costs and downtime)?

If we can not agree that a belt can be a potential liability we need to agree to disagree. I'm not about to change my mind. In fact reading about your Suburban has only reinforced my prejudice.