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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / July 2007parts of a regenerative braking system
Hi! I'm planning to modify my motorcycle to turn it into a hybrid bike (an experiment). I'm thinking of adding an electric motor mounted on the swing arm which would then drive the chain and the rear wheel. Most of the electric vehicles I've read about use brushless motors. Should it be an AC or a DC motor? How do I control the motor speed? Do I use some kind of variable resistor? a potentiometer? (whatever that is) Most, important, how do I turn the motor into regenerative brakes? Can anyone explain what's going on in the car electronics when the motors turns into regenerative brakes/generators? In a simple circuit, batteries would be connected to the motor and this motor is usually powered by the battery... but when regenerative brakes are used, the battery is still connected to the motor but this time, it is the motor which powers and recharges the batteries. Can anyone tell me WHAT makes regenerative braking happen? I already asked a few people and they say that generators/alternator have diodes to make electricity just flow out and not in. So is it possible to incorporate regenerative brakes with just the use of some diodes? If for example an electric car were running and then, at an instant, diodes were installed in the circuit between the battery and the motor, then would the motor turn into a generator and charge the batteries? Would there be a need for an inverter or a rectifier? Just curious--what kind of bike? A very interesting project, indeed. Might want to just kluge a kit from an electic car, which would have all this built in. BUT, I think you're a little behind an 8-ball, practicality-wise. Keep in mind that these motors, in an electric car, are dual purpose: alternately generating mechanical power to drive the car and then electric power to brake the car. In your application, it would be *robbing* mechanical power (to a small extent), and then only generating electric power for braking. As well as being cumbersome, etc. If you really wanted to experiment with regenerative power, take this concept and build a dynamometer for your bike! Same stuff, much more elegant application, imo. Might could use a treadmill motor, but not sure. Not the way real dynamometers work, from what I saw on the history channel or someplace, but just as valid. Real dynamometers physically measure a torque or force or sumpn.  Signature------ Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, but NOT for a Democrat or a Republican. Ending Corruption in Congress is the *Single Best Way* to Materially Improve Your Family's Life. The Solution is so simple--and inexpensive! entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs > Hi! > [quoted text clipped - 34 lines] > > Would there be a need for an inverter or a rectifier? Why then would it be robbing power? I don't get it. My plan is to use around four 12volt batteries connected in series to make a total of 48volts. and when the batteries run out of power then the engine's stator or alternator can recharge these batteries. Also, I have the option to charge the batteries at home. I guess it would be nice if the batteries have gauges to monitor their condition (volt meter, ammeter, etc) perhaps, you can recommend any company that sells brushless motors and regenerative brakes upgrades? Look for info here: http://www.fiveflagsmotorbikes.com/EFolder.htm http://www.wildernessenergy.com/ http://www.werelectrified.com/ SignatureCraigFL http://www.automotiveforums.com > Hi! > [quoted text clipped - 6 lines] > Most of the electric vehicles I've read about use brushless motors. > Should it be an AC or a DC motor? That depends on how complex a control system you are able to build. AC motors are more efficient, but particularly for variable speed, regenerative braking, and DC supply installations, much more complex. > How do I control the motor speed? Do I use some kind of variable > resistor? Only for the simplest DC motor > a potentiometer? (whatever that is) That's basically a variable resistor, but usually rated for small signal applications. Neither are terribly efficient solutions for power control. Pulse Width Modulation is better. > Most, important, how do I turn the motor into regenerative brakes? > Can anyone explain what's going on in the car electronics when the > motors turns into regenerative brakes/generators? With a DC motor, it involves increasing the motor field current which increases the motor's internal e.m.f. Once this exceeds the battery voltage, power starts flowing from the motor back into the battery. The motor becomes a generator. For an AC motor with a variable speed control, this involves advancing the AC phase and/or frequency to increase motor power or retarding it to cause the motor to generate. > In a simple circuit, batteries would be connected to the motor and > this motor is usually powered by the battery... but when regenerative > brakes are used, the battery is still connected to the motor but this > time, it is the motor which powers and recharges the batteries. > > Can anyone tell me WHAT makes regenerative braking happen? Any motor (AC or DC) will become a generator when driven above its no load speed by an external mechanical power input. When operating at a constant speed (driving along), the trick is to modify the input to the motor (field current, phase and frequency) to cause this no load speed to drop below your current cruising speed. > I already asked a few people and they say that generators/alternator > have diodes to make electricity just flow out and not in. Alternators do. > So is it possible to incorporate regenerative brakes with just the use > of some diodes? Nope. > If for example an electric car were running and then, at an instant, > diodes were installed in the circuit between the battery and the > motor, then would the motor turn into a generator and charge the > batteries? > > Would there be a need for an inverter or a rectifier? For an AC motor, yes. But its a lot more complex than a simple inverter. SignaturePaul Hovnanian paul@hovnanian.com ----------------------------------------------------------------------- Free the Mallocs! What would I need to do to advance the AC phase and frequency (whatever that means)??? Home come I read in some post that the only difference between a motor and a generator is the direction of the current/power flow? Thank you for the explanation but is there any other simpler explanation on how to turn the AC or DC motor into a generator? What should be done or added? > What would I need to do to advance the AC phase and frequency > (whatever that means)??? You'll need something like an inverter whose phase and frequency can be controlled based on numerous sensors and inputs. > Home come I read in some post that the only difference between a motor > and a generator is the direction of the current/power flow? That's the result. The way you get one to reverse its power flow is rather involved. > Thank you for the explanation but > > is there any other simpler explanation on how to turn the AC or DC > motor into a generator? > What should be done or added? Not really. Its a rather involved problem in power and control systems. You'll need to study up on the basics of electrical devices, motors, electromagnetics, etc. SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ Big business never pays a nickel in taxes, according to Ralph Nader, who represents a big consumer organization that never pays a nickel in taxes. -- Dave Barry Where can I get such an inverter? Any specific manufacturers? I've been reading a lot on motors, generators, inverter, rectifier and other electrical related stuff but all I get are information on how regenerative brakes work. but what I really need to know is what is needed to make such a thing work. Okay then, I will try to research more on controlling field current, phase and frequency. I thought I was getting closer to knowing the secret to regenerative braking but then I was wrong and it seems to be a long way until I complete it. > lethaldri...@gmail.com wrote: > [quoted text clipped - 27 lines] > taxes. > -- Dave Barry > Where can I get such an inverter? I'm not familiar with any systems sized for bicycles or motorcycles. The people that play around with this sort of thing on autos might be able to give you some advice. Try Googling "hybrid hacking" SignaturePaul Hovnanian paul@hovnanian.com ----------------------------------------------------------------------- Free the Mallocs! can you help me complete the list for components needed in an electric vehicle 1. brushless motor 2. motor speed controller 3. batteries 4. throttle control what else? Can one build a very basic electric vehicle with only these components? > can you help me complete the list for components needed in an electric > vehicle [quoted text clipped - 6 lines] > what else? Can one build a very basic electric vehicle with only > these components? That's a good outline for a basic system. Unfortunately, you aren't going to be able to walk into a parts shop with this list and walk out with anything useful. SignaturePaul Hovnanian mailto:Paul@Hovnanian.com ------------------------------------------------------------------ Some people are like Slinkies; they serve no specific purpose, but they bring a smile to your face when you push them down the stairs. hmmmm.... I think that using deep-cycle lead-acid batteries would be best for my applications. these batteries are used in golf carts and other electric utility vehicles and they are more tolerant to discharging. > lethaldri...@gmail.com wrote: > [quoted text clipped - 18 lines] > Some people are like Slinkies; they serve no specific purpose, > but they bring a smile to your face when you push them down the stairs. Remember the old bike safety-lite friction driven by the bicycle wheel? That seemed to me to be regenerative braking. Man, when that goddamm bulb was lit, you could really feel the drag! Disconnect the bulb (stop the current flow), and pedaling was really easier. Neat little generator. Mebbe I was just weak as sh.t, as well. :) Signature------ Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, but NOT for a Democrat or a Republican. Ending Corruption in Congress is the *Single Best Way* to Materially Improve Your Family's Life. The Solution is so simple--and inexpensive! entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs >> What would I need to do to advance the AC phase and frequency >> (whatever that means)??? [quoted text clipped - 17 lines] > You'll need to study up on the basics of electrical devices, motors, > electromagnetics, etc. actually I also did consider something like that. but instead of a dynamo, I'm using a car alternator which would be connected to the rear wheel by a pulley by a loose belt, and when I want regenerative brakes to work then I would tighten the belt with a tensioner. or the alternator belt could always be tight enough but the alternator wiring connection to the battery could be cut so that it won't be charging the battery when not needed. BUT I still think the motor-generator is a superior design since it's compact and lighter and turning the regenerative brakes is simpler (assuming that everything needed is in place) On Jul 21, 2:21 pm, "Proctologically Violated??" <entropic3.14de...@optonline2.718.net> wrote: > Remember the old bike safety-lite friction driven by the bicycle wheel? > That seemed to me to be regenerative braking. [quoted text clipped - 48 lines] > > taxes. > > -- Dave Barry > Hi! > [quoted text clipped - 34 lines] > > Would there be a need for an inverter or a rectifier? Indeed the electronic controls are the real high-tech part of hybrids. Do NOT use a variable resistor to control speed. Most of the hybrid systems I know of use a very complex electronic control system. The DC from the batteries is "chopped" into a hybrid signal, either AC (most common) or a pulsating DC. On braking the voltage from the motor is stepped up in a special voltage converter , then rectified to DC and fed to the battery. If you are not good in high power electronic control systems this part of the conversion will be something you need to farm out to an EE who is. The control system is basically a computer that takes into account the vehicle speed, acceleration or brake commands, battery charge level, and such, then computes how to modify the battery or motor generator voltages, and drives high power electronic voltage conversion electronics. I really do plan to ask for the help of an electrical engineer although I haven't found one who's good with motors/generators. about the control system, I think that it doesn't have to be very complicated since regenerative braking systems can be found on electric bikes. i still need an answer to the question: What makes motors different from generators/alternators? What parts make them different from each other? Is it possible to do it the other way around? What should be done to an alternator to convert it into a motor? Ask the motor/generator thing on rec.crafts.metalworking. These guys know a lot about motors/controls, 3 ph converters, pumps, the whole nine. Tell'em I sent you. :) Signature------ Mr. P.V.'d (formerly Droll Troll), Yonkers, NY Stop Corruption in Congress & Send the Ultimate Message: Absolutely Vote, but NOT for a Democrat or a Republican. Ending Corruption in Congress is the *Single Best Way* to Materially Improve Your Family's Life. The Solution is so simple--and inexpensive! entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs >I really do plan to ask for the help of an electrical engineer > although I haven't found one who's good with motors/generators. [quoted text clipped - 9 lines] > Is it possible to do it the other way around? What should be done to > an alternator to convert it into a motor? >I really do plan to ask for the help of an electrical engineer >although I haven't found one who's good with motors/generators. It's a different world. >about the control system, I think that it doesn't have to be very >complicated since regenerative braking systems can be found on >electric bikes. The question is whether you care about efficiency and battery life. If you don't care about efficiency, you just use a DC brush-type motor for power... you apply PWM to it and adjust the pulse width for speed control, then you reverse it and use the battery as a load with the same PWM device. Eventually this wrecks the battery since the battery wants to see a constant voltage and isn't happy as a random current sink, but it's the way a lot of those devices work. >i still need an answer to the question: >What makes motors different from generators/alternators? What parts >make them different from each other? A DC brush type permanent magnet motor is the same thing as a DC generator. But, there are plenty of other kinds of motors out there, and brushless motors and induction motors are totally different things and cannot easily be used in reverse. A DC universal motor has a field coil in place of the permanent magnet, and if it is supplied with DC, the motor can be used as a generator. If you look inside a typical hybrid golf cart, you will see a DC permanent magnet motor in most cases, which is used in reverse as a generator to charge the battery once the gasoline engine picks up at higher speeds. The Audel's Small Motor Repair Handbook has an introduction to the various kinds of motors. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." On Jul 23, 2:51 pm, lethaldri...@gmail.com wrote: > I really do plan to ask for the help of an electrical engineer > although I haven't found one who's good with motors/generators. [quoted text clipped - 9 lines] > Is it possible to do it the other way around? What should be done to > an alternator to convert it into a motor? Any electric motor will act as a generator, and vis versa. It depends on the rpm of the motor and the voltage feeding it or loading it.If something mechanical turns a motor faster than the applied voltage is trying to drive it, it will generate its own voltage/current and feed it back to the supply. But you need to step up the voltage to get it to charge properly. That voltage conversion is the high-tech part of the electronics. >Any electric motor will act as a generator, and vis versa. It depends >on the rpm of the motor and the voltage feeding it or loading it. No, not at all. For example, an induction motor relies on the current in the field coil to induce an opposing voltage in the armature. If there is no current to the field coil, there is no opposing voltage in the armature. You can spin it all you want and there will be no voltage on the leads. Now, any PM motor will act as a generator, and most universal motors can be easily rewired turn them into generators by providing external power for the field coil. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." >>Any electric motor will act as a generator, and vis versa. It depends >>on the rpm of the motor and the voltage feeding it or loading it. [quoted text clipped - 4 lines] > armature. You can spin it all you want and there will be no voltage on > the leads. Well, you CAN make an induction generator- but you have to have an excitation voltage present to make it work. In fact, if you take an ordinary induction motor and instead of having it drive a load, drive it FASTER than it "wants" to turn (ie, faster than its synchronous speed), it will in fact generate power and feed it back onto the supply grid. It just can't start from scratch, you have to put it on an AC grid to generate the induced currents in the armature before it can start generating. And, if you do this on a large scale as wind-power "farms" do, then you need to pay attention to things like power factor correction (relative phase between current and voltage) because induction motors and generators don't operate at unity power factor. But yeah, I agree that saying "every motor will act as a generator" without caveat is incorrect. If you want to use, say, a variable-frequency drive AC motor as a regenerative brake, its got to have a "smart" controller to make everything work right. Not the least part of which is deciding when to start applying the friction brakes smoothly and seamlessly so the driver gets however much stopping force he wants without noticing a change from regenerative braking to friction braking. A brushless motor is a stepping motor and requires some high- powered electronics to provide a rotating signal to the many leads of the motor. Not simple. And it won't act well at all as a generator. An automoble alternator will not act as a motor. Period. The simplest way is to use a series-wound DC motor with separate field and armature feeds so that forward, reverse and braking can be performed easily. Field current is always one polarity and armature current is reversible. Overall current is varied using solid-state devices like a MOSFET and some interface components. Braking is achieved by either shorting the armature leads together or connecting them to the battery, while the field is fed current varied to achieve the amount of braking desired.. You need first to get a course in basic electricity, then think about this again. It's much more involved than you think. The fact that there are few setups like this out there speaks for itself. Dan > A brushless motor is a stepping motor and requires some high- > powered electronics to provide a rotating signal to the many leads of > the motor. Not simple. A brushless DC motor is NOT a stepper motor. Two different animals entirely. Most brushless DC motors (as used in, for example, computer case fans) are actually very simple AC motors (either induction or hysteresis motors) with a small electronics package that turns the DC into an AC drive signal. A stepper motor is far more complex, and while it is technically a DC motor with no brushes, its a very unique sub-class. Okay I guess I should take a short course on Electricity or maybe read even more books or websites. But I guess I can't handle everything and I still have to leave the electrical/electronics part to the engineers since I'm already handling the mechanical part of the vehicle. But just for experimenting and testing, I guess I'll just look for the right kind of motor and a good controller such as Curtis.... although Curtis Controllers seem to be too expensive. I have a question... If there's a brushless DC motor then is there a brushless AC motor? Or are they just the same? I'm still confused here. > Dan_Thomas_nos...@yahoo.com wrote: > > A brushless motor is a stepping motor and requires some high- [quoted text clipped - 7 lines] > into an AC drive signal. A stepper motor is far more complex, and while > it is technically a DC motor with no brushes, its a very unique sub-class. >I have a question... >If there's a brushless DC motor then is there a brushless AC motor? A brushless DC motor is secretly a multiphase AC motor in disguise. Almost all AC motors are brushless. Most AC motors you see are induction motors, in which the changing magnetic field from the field coil induces current in a wire loop on the armature, which induces an opposite magnetic field in the armature, causing the armature to turn in the field of the field coil. No brushes required, but speed control is very limited. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." So do brushless DC motors need inverters when powered by car batteries?? What motor do you recommend for an electric car/bike? What kind of motor does Toyota use in their Prius? How about in golf carts? > <lethaldri...@gmail.com> wrote: > [quoted text clipped - 12 lines] > -- > "C'est un Nagra. C'est suisse, et tres, tres precis." guys, any inputs here? On Jul 28, 9:49 pm, lethaldri...@gmail.com wrote: > So do brushless DC motors need inverters when powered by car > batteries?? [quoted text clipped - 20 lines] > > -- > > "C'est un Nagra. C'est suisse, et tres, tres precis." >So do brushless DC motors need inverters when powered by car >batteries?? They need an electronic control unit which is usually built into the motor itself, which turns each coil on and off at the appropriate time. It's not really an inverter per se. >What motor do you recommend for an electric car/bike? For a bike, I might consider a permanent magnet motor with rare earth magnets, because they have a very high power to weight ratio and they occasionally turn up military surplus for cheap. >What kind of motor does Toyota use in their Prius? Dunno, I never took one apart. >How about in golf carts? Most use universal DC motors, with some sort of control system that adjusts the voltage on the field coil to vary the speed. This was an excellent design back in the seventies when control electronics were expensive. The efficiency is poor and there is no regenerative braking, but who cares? It's a golf cart. The worst that can happen is someone has to carry their own clubs. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." > But yeah, I agree that saying "every motor will act as a generator" > without caveat is incorrect. If you want to use, say, a [quoted text clipped - 4 lines] > he wants without noticing a change from regenerative braking to friction > braking. Yeah, I should have added the caveats. I was meaning that any motor type likely to be used in an electric or hybrid car. And for the variable f motors I did mean that they needed the smart controller. In fact, in an earlier post my contention was that the controller for a good hybrid was a pretty fancy piece of high power electronics. Smart and able to switch high current at high frequencies. >Yeah, I should have added the caveats. I was meaning that any motor >type likely to be used in an electric or hybrid car. And for the >variable f motors I did mean that they needed the smart controller. >In fact, in an earlier post my contention was that the controller for >a good hybrid was a pretty fancy piece of high power electronics. >Smart and able to switch high current at high frequencies. Right, the controller is really the hard part, and it's part of the reason why the electric car craze of the 1920s died. Back then, they used DC motors either with a rheostat in the field coil or with taps on the field coil to adjust speed over a fairly narrow range. This is inefficient, and efficiency is everything when you are trying to run off a limited capacity battery. These days with solid-state electronics it's a lot easier to make an efficient controller with a PWM circuit driving a big switching transistor driving the motor. But, because we have electronics, it's ALSO possible to go to more complex motor designs like the "brushless DC motors" which are really multipole AC motors with position sensors driven by a digital controller. Needless to say, regenerative braking makes the control system a _lot_ more complicated, because it first needs to reconfigure everything so the motor is rewired as a generator (with most motor designs) and secondly it needs to regulate the power produced for effective and efficient battery charging without damaging the battery and at the same time make sure the generator sees a constant load so that the drag it produces does not vary. --scott Signature"C'est un Nagra. C'est suisse, et tres, tres precis." lethaldri...@gmail.com wrote: >I'm planning to modify my motorcycle to turn it into a hybrid bike (an >experiment). >How do I control the motor speed? Do I use some kind of variable >resistor? a potentiometer? (whatever that is) A potentiometer is a variable resistor, and it's simply impractical to use for direct control at the power levels you're talking about. You could get by with large diodes and relays if everything is DC; otherwise you'll need large MOSFETs or IGBTs, but you can get by with SCRs and Triacs. Check www.epanorama.net, a site that covers everything electronic, and look not only for regenerative breaking but also for variable frequency drives, or VFDs, and hard disk drive motors and controllers (they use regenerative breaking). I'd seriously consider making my first prototype all-electric since regenerative braking alone is quite a project. |
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