Showing papers on "Dynamic braking published in 1980"

Dynamic Modeling of Brushless dc Motors for Aerospace Actuation

Abstract: A discrete time model for simulation of the dynamics of samarium cobalt-type permanent magnet brushless dc machines is presented. The similation model includes modeling of the interaction between these machines and their attached power conditioners. These are transistorized conditioner units. This model is part of an overall discrete-time analysis of the dynamic performance of electromechanical actuators, which was conducted as part of prototype development of such actuators studied and built for NASA-Johnson Space Center as a prospective alternative to hydraulic actuators presently used in shuttle orbiter applications. The resulting numerical simulations of the various machine and power conditioner current and voltage waveforms gave excellent correlation to the actual waveforms collected from actual hardware experimental testing. These results, numerical and experimental, are presented here for machine motoring, regeneration and dynamic braking modes. Application of the resulting model to the determination of machine current and torque profiles during closed-loop actuator operation were also analyzed and the results are given here. These results are given in light of an overall view of the actuator system components. The applicability of this method of analysis to design optimization and trouble-shooting in such prototype development is also discussed in light of the results at hand.

Dump truck with safety circuit

Abstract: An electrical circuit for driving an electrically driven vehicle such as a dump truck is capable of preventing occurrence of accidents caused by an erroneous operation and thereby increasing safety by providing an arrangement such that the vehicle cannot start unless all necessary operations have been completed before starting. For this purpose, a power source of a control box controlling an exciting current for a generator is turned on to generate the exciting current only when all necessary operations have been completed. This is achieved by connecting a plurality of switches corresponding to various operations in series to a power source relay and thereby causing the power source relay to be actuated upon closing of all of these switches. The circuit also enables the motors to be utilized as generators to provide dynamic braking for the truck.

Emergency braking system for continuously controlled rail vehicle - switching to steeper braking curve when braking control signal disappears

Abstract: The braking system is normally controlled in dependence on received braking requirement criteria, allowing one of a number of parabolic braking curves to be selected. The emergency braking is initiated if there is an interruption in the received data telegram. When emergency braking is put into operation the braking cycle is switched to a steeper braking curve (BK3) which will bring the vehicle to a halt in a shorter distance, instead of using the emergency braking curve (ZA). The vehicle is not brought completely to rest, if the transmission connection with the central control is re-established as the vehicle reaches a subsequent intact line conductor loop. Pref. the steepest normal braking curve (BK3) is used for emergency braking.

Induction motor controller

Abstract: PURPOSE:To simplify an induction motor controller by applying a three-phase control signal used at accelerating time to DC dynamic braking used between two phases of a primary voltage control three-phase induction motor. CONSTITUTION:A speed control circuit 1 produces a control signal 51a to a phase control circuit 51 upon reception of an instruction signal 2a from a speed instruction signal generator 2 and a speed signal 4a from a speed detector 4. When an acceleration signal is given, three-phase control gate signal is produced to SCR1-SCR6. When DC dynamic braking instruction is given then, three-phase control is shut off to apply a gate signal for synchronizing SCR6, 9 with SCR9, 10 to a single phase bridge circuit of SCR1, 6, 9, 10 to thus control the single phase for the DC dynamic braking operation.

Method and apparatus for dynamic braking in a motor control system

Abstract: A controlled current inverter motor control system including a controlled source of direct current for supplying a variable frequency inverter by way of a direct current link circuit which includes, within the link circuit, a selectively insertable dynamic braking resistive element. Upon a call for a dynamic braking mode of operation, the source of direct current is short circuited and the normal operational or running control of the motor is discontinued. Special circuitry is provided which then forces a special frequency control of the inverter to thus control the angle between the motor flux and motor current to a prescribed value proportional to the extant value of a motor operating parameter (motor current or motor flux) prior to the insertion of the dynamic braking resistive element into the link circuit.

Lim braking techniques for transit vehicles

Abstract: Methods of using a LIM and inverter propulsion system to decelerate urban mass transit vehicles are investigated using a mathematical model. Test data is presented to substantiate the performance of what are predicted to be the most useful and directly applicable techniques. It is concluded that regeneration to loads connected to the wayside power distribution system provides the most effective braking. The loads may be present already or may be introduced when vehicle deceleration commences. Another method of electrical braking, although demonstrated as feasible, will require to be supplemented by friction brakes to meet specified rates.

Protecting device for electric motor controlling switch

Abstract: PURPOSE:To improve the reliability of an electric motor driving means by employing a means for preventing a main power supply circuit and a braking circuit for the electric motor from being simultaneously closed, whereby the electric motor can be prevented from being erroneously started and stopped, so that a switch is never broken. CONSTITUTION:When an electric motor 1 is driven, a striking signal is input into a pulse transformer 6 so that a main loop circuit 19 is closed. As a result, one of main thyristors 2, 3 is turned on in accordance with the polarity of a power source to allow the electric motor 1 to be rotated. When the electric motor 1 is braked, a striking signal is input into a pulse transformer 9 so that a braking loop circuit 22 is closed. As a result, a dynamic braking power is applied to the electric motor 1. In a case where a command means is erroneously operated so that a striking command signal is applied to the pulse transistors 6, 9, a diode 21 is turned on to allow a transistor 5 to be turned off. Accordingly, the main loop circuit 19 is not closed; the braking loop circuit 22 only is closed. At this time, an electric current flowing through thyristors 2-4 is limited by a resistor 25a.

Brake for rotary body

Abstract: PURPOSE:To smoothly stop a rotary body which has a large moment of inertia, by automatically and electrically brake the rotary body by the counter electromotive force of a motor. CONSTITUTION:When a changeover switch SW is closed, the motor 102 is rotated through a resistor R1 and a transistor Q1. When the changeover switch is opened in response to a desired operation of the rotary body, a driving power source 101 is disconnected from the motor 102 and connected to an electromgnetic relay 105. At that time, a driving coil DC is energized, a normally closed contact ta is closed and a load resistor R2 is coupled in parallel with the motor 102. The counter electromotive force caused by the inertial rotation of the motor 102 is consumed by the load resistor R2, namely, dynamic braking is effected. The rotation of the motor is thus quickly and smoothly stopped.

Braking system for vehicle or machine - has fly wheel energy reservoir to store and return braking energy

Abstract: A gear drive connects the vehicle drive shaft with a flywheel. When the engine output torque falls to zero a clutch disconnects it from the shaft and a clutch connects the gear to the shaft. The kinetic energy of the vehicle is then absorbed by the flywheel which brakes the vehicle. The braking effect is varied by variation of the gear ratio. When the drive shaft ceases to rotate, a clutch disconnects the flywheel from the gear drive. The drive is reconnected when the vehicle is to be restarted so that the energy stored in the flywheel can be returned to the shaft.

Track braking system with automatic velocity control - has descent braking section adjusted in dependence on run-through velocity for control braking section

Abstract: The track braking system has a control braking section (RB) and a descent braking section, the former divided into initial, main and final rubber track braking stages (VB,HB,NB). The entry and exit velocities of the rail wagon for each stage (VB,HB,NB) are monitored to allow automatic braking release upon the required velocity being reached. The required run-through velocity for the control braking section is used to set the braking criteria of the descent braking section, to ensure that the control braking section is released before full passage of the wagon. Pref. the instant for evaluating the release state of the control braking section is provided by the point at which the last axle leaves the main braking stage (HB). The calculated required run-through velocity in the control braking section (RB) is dependant on the wagon loading.

Device for protecting chopper of electric motor vehicle

Abstract: PURPOSE:To simplify the construction of a device for protecting the chopper of an electric motor vehicle by operating a current detector for detecting the nonconductivity of a switch for connecting dynamic braking resistors also as a current detector for detecting the nonconductivity of the chopper. CONSTITUTION:A series circuit of a main thyristor chopper 15 and an air-core reactor 15 is connected to a main smoothing reactor 2, and a series circuit of an auxiliary thyristor 13 and a commutation capacitor 14 is connected in parallel with the previous series circuit. A switch 5 is connected in series with a dynamic braking resistor 4 to be connected when a regenerative braking load is ineffective. A current transformer 21 is so provided as to detect the nonconductivity of both the main thyristor and the switch 5 to thus simplify the protecting device.

The influence of the braking distance indication on the driver's behaviour

Abstract: TEST VEHICLE EQUIPPED FOR SETTING THE COEFFICIENT OF FRICTION BY PAVEMENT CONDITIONS AND MONITORING BRAKING DISTANCE

Braking control mechanism for rail vehicle - automatically adjusts braking force to prevailing conditions using force measurer attached to chassis

Abstract: The braking control mechanism compares a variable describing the braking force with a reference and uses the result to correct the braking force. The variable measurement is the braking moment at a given distance from the brake jaws. Alternatively, the frictional force at the brake jaw suspension may be measured. A transducer (30) is located in the braking system's suspension (24,25) engaging the vehicle's chassis (13). The transducer's output is coupled via a setting circuit (31,32) to a setting element (33) that changes the pressure of the fluid supplied to the spring housing (23).

The Impact of Dynamic Braking on Shaft Torgues

Abstract: Motivated by recent concern for the safe operation of turbine-generator shaft sections when subjected to various power system disturbances and switching operations, this paper examines the impact of dynamic braking on transient shaft torques. A study of this type is crucial in evaluating the undesirable effects, if any, of dynamic braking on the turbine-generator shaft system, if brake resistors are to be utilized for stability augmentation.

The coupling of proven reliability and modern performance on boston's no. 4 and no. 12 rapid transit cars

Abstract: With the advent of sophisticated, state-of-the-art transit systems, there appears to have arisen an attendant trade-off between reliability and performance. Typically, forced to prioritize, most operating properties will opt for reliability. Specification requirements for the new No. 4 and No. 12 MBTA rapid transit cars dictated the use of propulsion and braking systems whose reliability had been demonstrated throughout the years. The specification also required, however, the integration of these systems into a cohesive unit that exhibited modern day ride performance. This paper provides a brief description of each of the subject vehicles, and then traces the technical history of the endeavor to blend the electrical and pneumatic braking systems' tractive effort outputs into a uniform deceleration rate without the use of complex system feedback and interface networks.