Showing papers on "Dynamic braking published in 1984"

A Novel Method of Multistage Dynamic Braking of Three-Phase Induction Motors

Abstract: An effective braking system suitable for three-phase induction motor drives is discussed. Braking is achieved in four stages using an electronic switching circuit. Initially, a single capacitor is connected across two of the motor terminals allowing single-phase self-excitation. Following a certain speed drop, a second capacitor is added across the same terminals to sustain self-excitation and reduce the speed further. In the third stage magnetic braking is achieved by short circuiting the third terminal. Finally, the motor is brought to a standstill by dc injection. A method of determining minimum capacitor requirements is presented for both single-phase and symmetrical application. Experimental results are included, demonstrating the validity of theoretical results regarding capacitor requirements, and indicating the effectiveness of the proposed braking scheme.

Electric motor fault and dynamic braking protection system

Abstract: Electric traction motors for rapid transit cars provide a first saturable reactor for sensing the current imbalance between the input and output leads of traction motor circuit, a second saturable reactor for sensing the current imbalance between the branches of the motor circuit, a current sensor in the excitation winding of each reactor to sense the current increase during a fault, a latching relay and a stepping relay both responsive to the output of each current sensor. A mode relay responsive to the dynamic braking control of the transit car connects either the sensor for the first reactor or the sensor for the second reactor to the latching and stepping relays depending upon the operating mode of the car. The latching relay functions to both disconnect the traction motors from their voltage supply and disable the car dynamic braking system upon a fault in either mode of operation. A motorman's reset button is provided to reset the latching relay after a fault to energize the motors and braking system. The stepping relay counts the number of faults and, after a predetermined number of faults has been reached, disables the reset button so that only a separate reset button accessable to maintenance personnel may be used. The reactor excitation windings are powered from an inverter circuit. The inverter has a fail safe circuit responsive to its output which actuates the stepping and latching relays to disable the car motors and braking system when the inverter output fails.

Dynamic brake lights for vehicles

Abstract: The invention relates to the dynamic representation of the braking process in vehicles. The intensity and duration of the braking process is made visually and/or audibly perceptible. Depending on the intensity of the braking process, one or more lighting surfaces migrate according to a determined sequence and structure so that the precise perception of the dynamic braking process is conveyed to the traffic behind. The signal required for this is acquired from a generally known acceleration sensor. An electronic evaluation circuit produces a series of pulses for actuating the different light elements. Since the eye responds best to intermittent or migrating light surfaces, in this case the driver of the vehicle behind can react more quickly and with adapted braking force.

Method for determining the set braking torque for the various wheels of a vehicle

Abstract: A method for determining the set braking torque for the various wheels of a vehicle is described, in which signals varying as a function of the wheel speeds VRi and the vehicle speed VF are used for this purpose. The signals, from which the set braking torques are determined, are obtained in that the signals corresponding to the wheel speeds and the vehicle speed are fed through a specially designed Kalman filter.

Damping circuit for centrifuge

Abstract: PURPOSE:To decelerate a rotor within a short time without the formation of disturbance in a separated sample, by reversally damping an electric motor for rotatively driving a rotor until the number of rotation of said rotor is decelerated to a predetermined number of rotation, and then switching it into the state of dynamic braking to further decelerate the electric motor. CONSTITUTION:In the damping circuit for the electric motor of a centrifuge having a rotor 1 for separating a mixed solution containing a sample and said electric motor for rotatively driving the rotor 1, to stop the rotor 1 from the state of constant-speed rotation, the electric motor is reversally damped by damping resistors 17, 18, etc. until the number of rotation of said rotor is decelerated to a predetermined number of rotation, and then said electric motor is switched into the state of dynamic braking by the damping resistor 18 or the like to further decelerate the electric motor. That is, the reversal braking is switched into the dynamic one by changing the junctions of the contacts 8a, 9a of relays 8, 9 to decelerate the rotor within a short time during the deceleration of the rotor. Hence, the electric motor for rotating the rotor can be braked in a manner such that a separated sample is not disturbed.

A microprocessor based optimal quality control of dynamic braking

Abstract: A new control scheme namely optimal quality control using for power system dynamic braking is described in this paper. Dynamic braking is a effective measure for improving power system transient stability, and it has been in operation succesfully in many countries. The difference between the new scheme and the conventional scheme is that the braking resister removes not at the time of δ = 0, but at the suitable time of δ < 0 before circuit reclosing. The circuit reclosing time will also be selected automically by this scheme to minimize the post fault power angle oscillation. A microprocessor Z-80 can be used for this scheme to achieve the function mentioned before. A control program for a model system has been developed. Dynamic simulation of this control scheme verified that the expected function can be performed and the run time of the control was fast enough for transient stability requirement.