Dynamic braking
Wherein an electromotive brake or electrical generator brake, the kinetic energy and the potential energy of the moving mass is converted to electrical energy. It is basically a working in generator mode asynchronous motor or three-phase synchronous motor and wear-free.
General
Regarding the use of the electrical energy produced, there are two types:
- Will she be fed into the power supply line or trolley or in an energy storage device ( for example, a starter / accessory battery or high-performance capacitor ), one speaks of a regenerative brake or - because this energy is called regenerative braking - a recuperation.
- If they converted through electrical resistances to thermal energy, it is called a dynamic brake. This is true - if it is not just used for heating purposes - deprecated.
In addition, there is the possibility to carry out an emergency brake direct electrical short. In certain types of engine, an armature short-circuit braking can be used, in which the armature ( rotor of a DC motor ) is short-circuited. This procedure should only be used when the motor can not be slowed down sufficiently rapidly with above two methods, since the complete braking power occurs as heat in the motor and in the short-circuit device.
Since the braking action of electric motor brake with decreasing speed decreases, to pause and as a parking brake always requires an additional mechanical brake.
Be used electromotive brakes both as useful as a dynamic brake for electric locomotives, railcars, trolleybuses and motor vehicles, conveyors in mining or all cable cars, particularly ore transport and ropeways. In vehicles with diesel-electric drive, the application of electrical resistance brake is also possible and common.
Main advantages of this brake are
- Possible use (eg heating ) or recovery of energy (recuperation )
- Less wear of the mechanical brakes
The operating experience showed, however early on that in addition to the brakes traction motors used about 30 % must be interpreted more powerful than would be required for pure driving.
Applications
Rail transport
For motor brakes on electric and diesel-electric locomotives, the electric motor is switched to generator mode. The converted this "waste energy " is partially collected in accumulators for auxiliaries or implemented in braking resistors in heat. Electric locomotives possessed for heat dissipation through voluminous " Thruster " or braking resistors with air cooling on the roof. In cogwheel mountain railway and tramway vehicles ' braking power ' is passed in the winter in the radiator in the persons compartments. Are fed Especially with trams to the brake power the Solenoidbremsen the sidecar.
The braking power regeneration ( regenerative braking ) of electric vehicles based on the new possibilities of the traction converter. The braking energy is transformed again and fed back into the electrical catenary. In direct current paths ( eg tram) for feeding back not a line-commutated inverter is required, but the capacity of the traffic overhead contact line is only given if at least one of the following cases is true:
- Other vehicles drive on the same section and related energy
- The sub-station is capable of regenerative feedback ( active rectification / operating in four rather than two quadrants of the AC supply voltage )
- At the track are capacitors stations ( systems with double-layer capacitors ) for intermediate storage available
Therefore, the vehicles have to consider the capacity of the network and also have the possibility of dynamic braking and / or eventually lead capacitors for self- caching with. Usable for a criterion is the magnitude of the voltage. If it exceeds a maximum value, then it must be assumed that no buyer is available.
This is different dissolved in trying railcars Alstom Coradia LIREX. This train fed into the diesel version of a braking energy in a flywheel accumulator. Directions to the energy is returned from the memory. There are also Gyroantriebe without diesel engine, this charge the flywheel at the end points on; they are also useful for regenerative braking in the situation.
In the relatively young and little -tested concept of the solar path, the feedback of braking energy in the energy storage device, such as a battery or capacitor, sine qua non, the relatively low performance of current solar cells for an everyday operation is to be able to use it effectively enough.
2007 covered the German railway eight percent of their total electricity demand for railway operation, regenerated braking energy. Also in 2009, the company announced this value around 820 gigawatt hours.
Motor vehicles
For road vehicles, the electric motor brake can find with Gyroantrieb only for use with electric and hybrid vehicles, trolleybuses and vehicles, since only these have electric drive motors. The braking power and the amount of regenerative braking depends on the power of the electrical machine, the memory capacity and the free capacity of the energy storage.
Electric vehicles and hybrid electric vehicles use electric-motor braking to charge the vehicle battery. Known hybrid vehicles are the Toyota Prius and the Civic IMA from Honda. Since 2007, the BMW 1 Series are equipped with a manual transmission on a recuperation for charging the Starter-/Bordnetzbatterie. 3 and 5 Series followed a few months later. Partially double-layer capacitors are carried in addition to the accumulator, which are able to give or receive much greater excellence.
When Gyroantrieb (eg Gyrobusse ) the driving power is stored in a flywheel, which drives the vehicle engine via a generator. Electromotive brakes is possible by generator operation of the traction motors and motor operation of the flywheel generator. Vehicles with Gyroantrieb only have very short ranges. Therefore, the concept lends itself to, inter alia, on buses; they can upload their flywheel end-capped with a power supply.
Often the electromotive brake cooperates with the electro-hydraulic brake.