Use of braking energy

In a nutshell, if the motor is made to spin faster than the voltage supplied to it would be able to make it spin, it becomes a generator.

Can I quote this?

Thanks.

Hi Solaank,
The braking energy can be utilized to generate power with either a generator or an alternator. Thus the energy is converted to electricity rather than being dissipated as heat from friction. This is referred to as 'regenerative braking' and is being tried and utilized on a number of hybrid vehicles. A DC generator has an advantage in this environment because it can act as both a motor to help power the bike and also act as a generator by capturing the energy of braking and converting it to electricity. Good luck and have fun with your bicycle project.

Refer to electrone above. AC or DC it works, AC is more complicated (electronics) but much more efficient that is why AC is replacing DC in traction applications, that and adhesion factor.

I'd like to know more about this?
Thanks (< 8

Do a search for AC traction you will find some very interesting concepts. Adhesion factor refers especially to Locomotives but can be related to trucks etc. In a nutshell it is the ability to get power to the ground without wheel spin. It is the key to the extra eficiency of AC traction over all current rival technologies. DC traction is much more efficient than mechanical transmissions and differentials. AC takes this even further, even without slip and slide control an AC powered wheel can only speed up a small amount because as it loses its slip frequency it loses torque. In an active control system as used in Locos and Haulpaks, transducers quickly detect the wheelslip and back off the inverter supplying that wheel (or axle for Locos, the other wheel(s) can just motor on, or if needed compensate for the lost torque until the slipping wheel regains grip. Slip frequency is the amount slower than synchronous frequency that rotor of an induction motor must run to receive the induced current required to generate torque. For instance a four pole 50hz induction motor will typically run about 1440rpm. Synchronous speed at 50hz is 1500rpm.

Ok, technically a motor converts electricity to mechanical energy. A generator is a device for converting mechanical energy to Direct Current and an Alternator converts mechanical energy to Alternating Current. In practice "Generator" is often used interchangeably. DC motors and Generators required a commutator to reverse the fields in order to enable continuous motion in the case of a motor or DC output in the case of a generator. Alternators use a slip ring to provide power (DC in your car, say) to a field rotor and you get AC power from the stator coils which is then rectified by diodes to get back to DC to charge your battery. Any motor can be a generator or vs-vs although there are often design optimizations that make the device function more efficiently one way than the other. Nowadays with solid state controls it is easy to construct a brushless multiphase AC motor that also works well to generate power. Electro-Magnetic Drive (EMD) locomotives use a large diesel engine that operates a generator that then powers six large DC motors that fill almost the entire space between the wheels. The advantage is no clutch or gears which becomes a big deal when you consider that an engine may be cranking out nearly a megawatt of power. Also, you can do dynamic breaking by switching the traction motors to generators and routing them into large resistive grids in the top of the locomotive. You may have seen large fans on top of a locomotive an those are to cool the grid. Slowing down a long train amounts to dumping quite a large quantity of energy into heat and done in this manner saves a great deal of maintenance on friction bases brakes. So on the bicycle, breaking is probably accomplished by heavy charging of the battery. Batteries can only accept so much current so they probably either limit the amount of dynamic breaking that is available. To do more they would have to add a resistive sink to dissipate excess energy into the environment but that is inconsistent with keeping the device cheap so it is doubtful they do that. Get a book on basic electromagnetic devices if you require a primer on how magnetism and electricity are related with regard to electromotive devices. Good luck!

Hi rcapper, Nice response and technical info and detail

Thanks! I enjoy this site. I get to learn some things and share some things I know.

Good stuff, Current Locos produce 4 megawatts the big ones are mostly AC. Unfortunately they still dump the dynamic braking energy into the atmosphere. There has been a lot of work done recently by companies such as MTU and ABB and CSIRO to overcome this waste. MTU have high temperature fuel cells of high efficiency, ABB are working on energy storage (one of their engineers told me about their "fuelless fuel cells" with chemical reactions far in excess of conventional datteries and CSIRO have had major success using latent heat storage. The future of surface transportation, in my limited view, is electric drives, probably 3 phase AC with efficient storage of retard energy (dymanic Braking) and top up from renewable sources. Maybe I'm dreaming, but our inventers like the bloke that started this story will lead the way. Go for it.

If I have an electric motor already what would I have to add to it to get generation to the lead acid batteries that I use?

Mechanical energy. If the motor is spinning then current is either flowing in or out. If current is going in and mechanical energy is being generated it's a motor. If mechanical energy is going in and electrical current is coming out, it's a generator. Note that not all motors make great generators and vs-vs but that's beyond the scope of of this venue.

Power

so there is not any additional circuitry that I would need to recharge the batteries I have a ZAP Exprs electric bicycle motor bike kit and I want to extend the range

Hey Solaank,check out Panasonics website,they build an electric bike.

Well, things got a little more complicated than just turning a DC or AC motor into a generator or alternator, respectively. The motor uses no brushes, commutators or slip rings, so it is obviously a permanent magnet, electronically commutated motor, otherwise known as a Brushless DC Motor (BLDC Motor). Synchronous motors are similar and typically have permanent magnet rotors while the fields are excited by AC power, which produces a "rotating" field. Now things get more fun: Check out Two-pole BLDC Motor Animation to get an idea of how they work. BLDC motors are constructed very much like AC synchronous motors, but the DC power source, such as a battery, is converted to an alternating power source electronically by switching the polarity of the DC current through the electromagnetic, stationary, field coils. When a permanent magnet rotor is turning between the stationary field coils of such a motor, it becomes an alternator. By rectifying the alternating current, the battery can be recharged with the correct polarity. Energy is returned to the battery by reducing the momentum of the bike as it converts mechanical energy to electrical energy.

Great, Try GE Transportation website.

Thanks Bill (< 8