2009 Hot Weather High RPMs?
#31
06-25-2009, 10:22 AM
Re: 2009 Hot Weather High RPMs?
To refine gpsman1's point about gear ratios: the traction motor is geared directly to the ring gear and therefor to the output of the transaxle. Its AC frequency is directly proportional to speed.
The other two components in this dynamic system are geared to each other through the planetary gearing. The actual gear ratios are fixed. What the controller does is change the AC frequency to either synchronous machine to regulate how torque is distributed.
In the case we are talking of, some ICE output torque (as in rpm) is sent to the generator generating power which is then sent to the traction motor as additional power (if the battery needs charging some will go there too). In a sense, when this happens it does change a "gear ratio" electrically, but the traction motor really remains hard geared to the axles.
In my initial thinking I thought that the AC frequency to the traction motor and generator was the same... I now believe that cannot be. The power conditioner has to be using different frequencies to each machine.
If someone has some hard info that says they are connected in parallel let me know. I've gone through the manuals in detail to determine this.
The other two components in this dynamic system are geared to each other through the planetary gearing. The actual gear ratios are fixed. What the controller does is change the AC frequency to either synchronous machine to regulate how torque is distributed.
In the case we are talking of, some ICE output torque (as in rpm) is sent to the generator generating power which is then sent to the traction motor as additional power (if the battery needs charging some will go there too). In a sense, when this happens it does change a "gear ratio" electrically, but the traction motor really remains hard geared to the axles.
In my initial thinking I thought that the AC frequency to the traction motor and generator was the same... I now believe that cannot be. The power conditioner has to be using different frequencies to each machine.
If someone has some hard info that says they are connected in parallel let me know. I've gone through the manuals in detail to determine this.
#32
06-25-2009, 10:29 AM
Re: 2009 Hot Weather High RPMs?
Desert Dog,
Please post for all to see the equation for generated power in a three phase, synchronous machine that is generating. You recall... N as in rotational rate & flux strength as in excitation, or something like that.
Then maybe we can get to how this dynamic system is creating, converting, and then consuming power.
Please post for all to see the equation for generated power in a three phase, synchronous machine that is generating. You recall... N as in rotational rate & flux strength as in excitation, or something like that.
Then maybe we can get to how this dynamic system is creating, converting, and then consuming power.
#33
06-26-2009, 08:02 AM
Re: 2009 Hot Weather High RPMs?
In the absence of an equation from desertdog, attached is a discussion of synchronous machines. It's a bit of a slog with the math equations and such (but it is partly a college professor's homework assignment!).
To simplify that discussion for the FEH:
The discussion presumes connection to the "infinite 60hz bus" of our national power grid which would fix machine rpm. Since our machine is only connected through rectifier & inverter packs, rpm & frequency can be varied at will.
The excitation to the rotor is a permanent magnet and so the magnetic field is a constant value and voltage output becomes solely a function of rpm.
The generator is connected to the sun gear of the planetary set with the ICE connected to the planet carrier.
Since the traction motor is geared directly to the ring gear and the wheels, its rpm, when on speed control, is controlled to maintain FEH speed. In the positive split mode of operation of the FEH system, some power from the ICE is given to the ring gear and some is passed to the generator. Speed is determined by the frequency supplied to the traction motor.
You'll note in the attached paper that power transferred by a synchronous machine with regulated frequency is determined by the torque angle between the rotating field created in its stator by applied AC power and the field on its rotor (permanent magnet).
The transaxle controller & power conditioner does this by regulating the engine and generator rpm. With a fixed permanent magnet in the generator the only way more power can be generated to assist the traction motor is to raise its rpm.
This effectively raises output voltage and therefore current. Thus I believe the Ford software is programmed to apply a certain rpm to the generator, via the ICE, to produce the desired voltage and therefore current.
Since the output of the generator, although AC, is rectified, frequency is irrelevant and, with a 3 phase system, there is no time dependency to the power output.
In our case the frequency applied to the traction motor is controlled to control speed and so it increases power by increasing its torque angle. Of course with this goes an increase in current into the machine. It is possible the the controller increases voltage also, which would then reduce torque angle, but we'd have to know just how Ford setup the software.
To simplify that discussion for the FEH:
The discussion presumes connection to the "infinite 60hz bus" of our national power grid which would fix machine rpm. Since our machine is only connected through rectifier & inverter packs, rpm & frequency can be varied at will.
The excitation to the rotor is a permanent magnet and so the magnetic field is a constant value and voltage output becomes solely a function of rpm.
The generator is connected to the sun gear of the planetary set with the ICE connected to the planet carrier.
Since the traction motor is geared directly to the ring gear and the wheels, its rpm, when on speed control, is controlled to maintain FEH speed. In the positive split mode of operation of the FEH system, some power from the ICE is given to the ring gear and some is passed to the generator. Speed is determined by the frequency supplied to the traction motor.
You'll note in the attached paper that power transferred by a synchronous machine with regulated frequency is determined by the torque angle between the rotating field created in its stator by applied AC power and the field on its rotor (permanent magnet).
The transaxle controller & power conditioner does this by regulating the engine and generator rpm. With a fixed permanent magnet in the generator the only way more power can be generated to assist the traction motor is to raise its rpm.
This effectively raises output voltage and therefore current. Thus I believe the Ford software is programmed to apply a certain rpm to the generator, via the ICE, to produce the desired voltage and therefore current.
Since the output of the generator, although AC, is rectified, frequency is irrelevant and, with a 3 phase system, there is no time dependency to the power output.
In our case the frequency applied to the traction motor is controlled to control speed and so it increases power by increasing its torque angle. Of course with this goes an increase in current into the machine. It is possible the the controller increases voltage also, which would then reduce torque angle, but we'd have to know just how Ford setup the software.
#34
06-26-2009, 12:56 PM
Join Date: Apr 2008
Location: Los Angeles
Posts: 895
Re: 2009 Hot Weather High RPMs?
In the absence of an equation from desertdog, attached is a discussion of synchronous machines. It's a bit of a slog with the math equations and such (but it is partly a college professor's homework assignment!).
To simplify that discussion for the FEH:
The discussion presumes connection to the "infinite 60hz bus" of our national power grid which would fix machine rpm. Since our machine is only connected through rectifier & inverter packs, rpm & frequency can be varied at will.
...
In our case the frequency applied to the traction motor is controlled to control speed and so it increases power by increasing its torque angle. Of course with this goes an increase in current into the machine. It is possible the the controller increases voltage also, which would then reduce torque angle, but we'd have to know just how Ford setup the software.
To simplify that discussion for the FEH:
The discussion presumes connection to the "infinite 60hz bus" of our national power grid which would fix machine rpm. Since our machine is only connected through rectifier & inverter packs, rpm & frequency can be varied at will.
...
In our case the frequency applied to the traction motor is controlled to control speed and so it increases power by increasing its torque angle. Of course with this goes an increase in current into the machine. It is possible the the controller increases voltage also, which would then reduce torque angle, but we'd have to know just how Ford setup the software.
I'm sure I'm missing something here...
#35
06-27-2009, 06:58 AM
Re: 2009 Hot Weather High RPMs?
Its not a series hybrid. Look up some of the web planetary gear set sites.
The traction motor is directly geared to the wheels and ring gear, while the ICE goes into the planetary carrier gears and the generator to the sun.
The transaxle controller regulates the frequencies to the traction motor & generator and ICE rpm to make the car go.
The traction motor is directly geared to the wheels and ring gear, while the ICE goes into the planetary carrier gears and the generator to the sun.
The transaxle controller regulates the frequencies to the traction motor & generator and ICE rpm to make the car go.
#36
06-27-2009, 08:13 AM
Re: 2009 Hot Weather High RPMs?
Another element of this is that the transaxle controller is adjusting things to minimize ICE emissions. It can run the generator in either direction, or "freeze" it to enable the ICE to transfer power to the ring gear (of course the ICE is unidirectional). Effectively it regulates generator rpm to generate, absorb (look up negative split mode), or transfer power.
This negative split mode seems designed to use the ICE characteristic of gasoline engines for compression braking to absorb power.
In the end, if the wheels are moving, the traction motor is moving, the rest is determined by minimizing ICE emissions while responding to the demanded power by the driver.
The first time I "floored" the gas pedal I was amazed at the acceleration, when you run both machines as motors and take the ICE to full power, this thing really moves out!
This negative split mode seems designed to use the ICE characteristic of gasoline engines for compression braking to absorb power.
In the end, if the wheels are moving, the traction motor is moving, the rest is determined by minimizing ICE emissions while responding to the demanded power by the driver.
The first time I "floored" the gas pedal I was amazed at the acceleration, when you run both machines as motors and take the ICE to full power, this thing really moves out!
#38
06-27-2009, 11:10 AM
Re: 2009 Hot Weather High RPMs?
Professor desertdog,
I have attempted to post a couple of private messages but your box is full.
Throughout your discussions you have conveniently used a crossing of the traction motor, held at a constant frequency by the speed controller and the generator. Look up how the system works in positive spit mode.
Second you seem to all too conveniently leave torque angle (which I called lag angle earlier-torque angle is the more proper term) out of your words. Increasing torque angle, at constant frequency and constant rotor excitation, is how synchronous machines increase power (& of course current flow into the machine).
In your most recent private message to me, where you describe what you're going to show me this weekend, you talk of how an FEH can climb a hill at the same speed as level ground. The key to this specific discussion is torque angle, why did you leave it out?
I have attempted to post a couple of private messages but your box is full.
Throughout your discussions you have conveniently used a crossing of the traction motor, held at a constant frequency by the speed controller and the generator. Look up how the system works in positive spit mode.
Second you seem to all too conveniently leave torque angle (which I called lag angle earlier-torque angle is the more proper term) out of your words. Increasing torque angle, at constant frequency and constant rotor excitation, is how synchronous machines increase power (& of course current flow into the machine).
In your most recent private message to me, where you describe what you're going to show me this weekend, you talk of how an FEH can climb a hill at the same speed as level ground. The key to this specific discussion is torque angle, why did you leave it out?
#39
06-27-2009, 05:30 PM
Re: 2009 Hot Weather High RPMs?
Professor desertdog,
I have reflected on the absence of torque angle in synchronous machine power production in all of your postings on this issue.
It is so fundamental that in the college paper I posted to this thread a few posts above that in the equation for torque (equation 1 in that paper) it is there setting the stage for the rest of the discussion.
Simply the torque output of a synchronous machine is:
T=Fs X Fr X Sin(delta) (recorded as equation (1) in that paper)
Where Fs is the magnitude of the stator field, Fr is the magnitude of the rotor field and delta is the angle between them. If you understand the sine tables you recognize that with increasing angle, up to 90º, the sine increases and thus torque (& power output) increase at constant motor rpm.
Of course if you vary the field magnitude you can vary the torque angle, but my point is that you can't vary the rotor since it's a permanent magnet. So your only control is the magnitude of the stator field and its frequency.
This is precisely why the FEH can maintain a constant speed with varying load (or hill climbing if you like). ...And this precisely why the only way to vary the output power of the generator is by varying its rpm.
Please tell me you get this.
This is so fundamental to synchronous machinery that it just took me awhile to trigger on its absence in all of your postings.
I have reflected on the absence of torque angle in synchronous machine power production in all of your postings on this issue.
It is so fundamental that in the college paper I posted to this thread a few posts above that in the equation for torque (equation 1 in that paper) it is there setting the stage for the rest of the discussion.
Simply the torque output of a synchronous machine is:
T=Fs X Fr X Sin(delta) (recorded as equation (1) in that paper)
Where Fs is the magnitude of the stator field, Fr is the magnitude of the rotor field and delta is the angle between them. If you understand the sine tables you recognize that with increasing angle, up to 90º, the sine increases and thus torque (& power output) increase at constant motor rpm.
Of course if you vary the field magnitude you can vary the torque angle, but my point is that you can't vary the rotor since it's a permanent magnet. So your only control is the magnitude of the stator field and its frequency.
This is precisely why the FEH can maintain a constant speed with varying load (or hill climbing if you like). ...And this precisely why the only way to vary the output power of the generator is by varying its rpm.
Please tell me you get this.
This is so fundamental to synchronous machinery that it just took me awhile to trigger on its absence in all of your postings.
#40
06-28-2009, 12:42 AM
Re: 2009 Hot Weather High RPMs?
Professor desertdog,
I have reflected on the absence of torque angle in synchronous machine power production in all of your postings on this issue.
It is so fundamental that in the college paper I posted to this thread a few posts above that in the equation for torque (equation 1 in that paper) it is there setting the stage for the rest of the discussion.
Simply the torque output of a synchronous machine is:
T=Fs X Fr X Sin(delta) (recorded as equation (1) in that paper)
Where Fs is the magnitude of the stator field, Fr is the magnitude of the rotor field and delta is the angle between them. If you understand the sine tables you recognize that with increasing angle, up to 90º, the sine increases and thus torque (& power output) increase at constant motor rpm.
Of course if you vary the field magnitude you can vary the torque angle, but my point is that you can't vary the rotor since it's a permanent magnet. So your only control is the magnitude of the stator field and its frequency.
This is precisely why the FEH can maintain a constant speed with varying load (or hill climbing if you like). ...And this precisely why the only way to vary the output power of the generator is by varying its rpm.
Please tell me you get this.
This is so fundamental to synchronous machinery that it just took me awhile to trigger on its absence in all of your postings.
I have reflected on the absence of torque angle in synchronous machine power production in all of your postings on this issue.
It is so fundamental that in the college paper I posted to this thread a few posts above that in the equation for torque (equation 1 in that paper) it is there setting the stage for the rest of the discussion.
Simply the torque output of a synchronous machine is:
T=Fs X Fr X Sin(delta) (recorded as equation (1) in that paper)
Where Fs is the magnitude of the stator field, Fr is the magnitude of the rotor field and delta is the angle between them. If you understand the sine tables you recognize that with increasing angle, up to 90º, the sine increases and thus torque (& power output) increase at constant motor rpm.
Of course if you vary the field magnitude you can vary the torque angle, but my point is that you can't vary the rotor since it's a permanent magnet. So your only control is the magnitude of the stator field and its frequency.
This is precisely why the FEH can maintain a constant speed with varying load (or hill climbing if you like). ...And this precisely why the only way to vary the output power of the generator is by varying its rpm.
Please tell me you get this.
This is so fundamental to synchronous machinery that it just took me awhile to trigger on its absence in all of your postings.
Drive in EV without variable gearing from the traction motor to the drive shaft.
Control regen without variable gearing.
Re-start the ICE in a smooth manner.
Charge the battery while controlling ICE to axle ratio.
Since you have begun referring to me as professor, I assume derisively, I have made a short quiz for you to take regarding the FEH. It should not take too long for you to do, maybe 15 or 20 minutes.
The references are the following:
1.) Ford Powertrain Control/Emission Diagnosis Manual
2.) 2006 Escape,Mariner,Escape Hybrid Workshop Manual
3.) Comparative Assesment of Hybrid Vehicle Powersplit Transmissions, Dr. John Miller
4.) Emerging Technologies of Hybrid Electric Vehicles, Dr. Chris Mi
1.) From the maximum power curves shown in slide 34 of reference 4, plot the torque-speed envelope curves for the traction motor and the generator for the FEH. Identify and label breakpoints. You may use piece-wise linear approximations for noisy data. Assume maximum traction motor power of 70kW and generator maximum power of 30kW.
2.) Given the traction motor to vehicle speed ratio from the Ford PC/ED Manual and the fact that the ring gear has 79 teeth and the sun gear has 33 teeth, write the equation of motion for the sun gear as a function of ICE RPM and traction motor RPM. Assuming that the tire size yields 750 revolutions/mile, compute the gear ratio of the traction motor to the ring gear and the ring gear to the axle.
3.) From the results above, compute the generator speed for a vehicle speed of 75MPH and an ICE RPM of 2500. Repeat for an ICE RPM of 3500.
4.) In an FEH, the generator goes from an operating state of 1kw @3800 RPM to 10kw @ 3500 RPM. Draw the trajectory on the 4-quadrant torque-speed curves for the generator. Give an example scenario of FEH operation that could result in this.
Simple enough. I look forward to seeing your answers.
