Showing papers on "Dynamic braking published in 1985"

Combined regenerative and friction braking system for a vehicle

Abstract: A vehicle supported for rolling movement on a track by a first set of wheels driven by an electric motor and a second unpowered set of wheels is provided with an improved braking system. The braking system includes a brake pedal which can be depressed to generate a brake demand signal, a regenerative braking system associated with the electric motor, and a friction braking system attached to the unpowered wheels. Control circuitry which regulates the operation of the two brake systems serves normally to actuate the regenerative braking system in response to the brake demand signal and to actuate the friction braking system only when the brake demand signal exceeds a predetermined level which corresponds normally to the maximum regenerative braking available. Under slippery rail conditions, a detector indicates slippage of the wheels relative to the rails during regenerative braking, and immediately actuates the friction braking system to produce additional braking in proportion to the brake demand signal. The braking system thus maximizes regeneration under optimal rail conditions and enhances braking under poor rail conditions.

Automotive yaw-sensitive brake control system

Abstract: Automotive brake control is performed by controlling brake pressure at front and rear wheels independently. The braking force at each of the front and rear wheels is controlled in accordance with monitored vehicle driving conditions so that the steering characteristics of the vehicle are held to predetermined characteristics even when vehicular brakes are applied during cornering. The braking pressure at front wheels is decreased when understeer characteristics increases due to braking. On the other hand, the braking pressure at the rear wheel is decreased when oversteer characteristics increases due to braking.

Brake control system

Abstract: o A brake control system for a multiple unit train of mixed motor cars and trailer cars - of the type usually to be found operating as metro or mass transit trains - and in which the motor cars have dynamic brakes operation of which is blended with, but given preference over, the friction brakes of all units. A brake demand signal calling for a given level of train retardation is weighted on each vehicle, according to the load of the vehicle, and the level of dynamic braking effort invoked on each motor car is limited in accordance with a maximum adhesion level calculated in proportion to the measured load of that car. In a modified arrangement the adhesion level is calculated in accordance with the load of the lightest loaded motor car. Signals representing the amount of dynamic brake effort achieved by each motor car is supplied to a trailer car and subtracted from the load weighted braking effort for the trailer car and the result used to actuate the friction brakes of the trailer.

Augmentation of Transient Stability Limit of a Power System by Automatic Multiple Application of Dynamic Braking

Abstract: Dynamic braking is known to be a powerful method of augmenting transient stability margins. Investigations of analytical studies supported by experimental verification using micro-machine model of a power system, are presented. A simple strategy based on speed deviation signal has been developed and successfully utilized for automatic single or multiple insertion of braking resistor, whenever required. The stability limit for a transient three phase fault is found to be appreciably raised. A fair degree of agreement between the analytical and experimental results enhances confidence in their reliability.

A Theoretical Analysis on Vehicle Cornering Behaviours in Braking and in Acceleration

Abstract: (1985). A Theoretical Analysis on Vehicle Cornering Behaviours in Braking and in Acceleration. Vehicle System Dynamics: Vol. 14, No. 1-3, pp. 140-143.

Anti-plug reversing module

Abstract: An anti-plug reversing circuit for use with a variable speed D.C. motor which provides safe and fast motor reversing with dynamic braking. The circuit, by sensing counter-EMF, prevents the premature application of a voltage of opposite (reversing) polarity until the motor armature has come to a full stop. The circuit advantageously utilizes a three-wire control input, is low cost, easily manufactured and applicable for use with low cost D.C. motors.

Emergency dynamic braking system of servomotor

Abstract: PURPOSE: To reduce the number of parts having larger current capacity and to lower the cost of a controller and compact it by adding a function of dynamic braking on the abnormality of load to a discharge circuit used for inhibiting the rise of intermediate voltage. CONSTITUTION: When a protective circuit 20 drives each transistor T 1 ∼T 6 for an inverter circuit 6 while the overcurrents of a servomotor 7 are detected by an overcurrent detector 21, several transistor T 1 ∼T 6 is interrupted while a main switch 1 is opened. The main switch 1 is opened while a contact 14 is brought to an ON state, a switching transistor 9 is turned ON, and the charging voltage of a capacitor 4 lowers. When the charging voltage of the capacitor 4 is lower than generated voltage by the servomotor 7, the generated voltage of the servomotor 7 charges the capacitor 4 through diodes D 1 ∼D 6 , thus generating regenerative action in the servomotor 7. COPYRIGHT: (C)1987,JPO&Japio

Electric braking performance of multiple unit trains

Abstract: Operation of a transit system is always a compromise between the two conflicting requirements of high average speeds, which not only improve the acceptability of rail travel to passengers, but also reduce the number of cars needed to run the service, and low "energy consumption" and "maximum demand", to reduce the operating electricity costs. Efficient use of regenerative braking can further these aims, by raising the voltage at the train power pick up for the former and by the use of regenerative energy return for the latter. Electric braking also allows higher deceleration rates with more controllability but without increased brake maintenance. There are two modes of electric braking, rheostatic and regenerative. The optimum choice of electric braking for a particular system depends upon the relative importance to the operator of a number of factors as well as local circumstances. This paper highlights some of the conflicting factors and illustrates their inter-relationships.

Reduction of peak dynamic loads on pumping units of main canal stations

Abstract: 1. The method of dynamic braking is recommended for reducing peak dynamic loads when stopping axial- and diagonal-flow pumps at stations of main canals. This method makes it possible with insignificant additional equipment to completely eliminate the most dangerous regime of stopping overspeeding — and to keel the pump in the optimal zone of the turbine regime, the loads in which are less than the corresponding loads in the working pump regimes. 2. As a result of investigating dynamic braking, data were obtained which characterized this method both from the viewpoint of a change in the electrical and in the hydromechanical parameters of the pumping unit. The optimal exciting current of the rotor is Ir*=0.4–0.6, in which case a current Ist*=0.6–0.8 is induced in the stator. Vibrations are reduced by threefold and pressure fluctuations by 2–2.5 times. Reversing of the hydrodynamic moment on the pump vanes is eliminated. 3. The proposed method of reducing peak loads solves difficulties related with transients at large pumping stations of water-transfer systems.

Dynamic Braking of Induction Motors Using DC Injection

Abstract: Dynamic braking of 3-phase induction motors through dc injection in commonly used in applications such as cranes and hoists. The paper analyses the performance of a slip ring induction motor with dc injection and derives expressions for the optimum values of injection voltage and rotor resistance. Digital computer simulation of the sequence of operations like motoring and braking is also given.