scholarly journals EXPERIMENTAL STUDY OF THE STATIC CHARACTERISTICS OF THE SYNCHRONOUS MACHINE IN THE MODE OF DYNAMIC BRAKING WITH INDUCTION RESISTANCE IN THE WINDING OF THE STATOR

2021 ◽  
Vol 2 (37) ◽  
pp. 22-27
Author(s):  
S. Kolychev ◽  
A. Sianov
Keyword(s):  
Mechanical Characteristics ◽  
Experimental Studies ◽  
Synchronous Machine ◽  
Stator Winding ◽  
Excitation Current ◽  
Current Frequency ◽  
Speed Sensor ◽  
Electromagnetic Moment ◽  
Braking Torque ◽  
Dynamic Braking

The article discusses the results of a study of the static electromechanical characteristics of a synchronous machine (SM) when prototypes of induction resistances (IR) with improved parameters are included in its stator circuits. Widespread in practice, dynamic braking (DB) of synchronous machines provides for the dissipation of the kinetic energy of the rotor in the resistance boxes included in the stator winding. In the process of stopping, to maintain the constancy of the average braking torque of the SM, a bulky relay-contactor shunt circuit for stator resistances is used. At low speeds, regulation of the excitation current of the SM or its forcing can also be applied. However, it is not possible to eliminate significant fluctuations in the electromagnetic moment in this way. To optimize the SM DB process, instead of resistance boxes, it was proposed to include a three-phase induction resistance in the stator winding, the value of which automatically decreases along with the stator current frequency. This approach allows you to drastically reduce the number of contact equipment and ensure smooth braking of the machine with electromagnetic moment fluctuations within narrow limits. Known IR designs are designed for asynchronous motors with a phase rotor and satisfy the requirements of the given quality factor of their starting characteristics, but cannot ensure the constancy of the torque on the SM shaft in the DB mode. Therefore, the objective of the work is to improve the design of the IR and obtain the necessary inhibitory mechanical characteristics of the SM using experimental studies. The work provides a pilot plant diagram and a drawing explaining the design features of the IR. The studies were performed for a synchronous machine, type МСА-72 / 4А, equipped with a thyristor exciter and a speed sensor. In three phases of the SM stator, IRs connected by a "star" were turned on. The experiments were carried out in the direction of obtaining the necessary braking characteristics of the SM by varying the design of the internal elements of the IR. The figures show the mechanical characteristics of the SM obtained in the process of studying the effect on them of the thickness of the inner steel rings and massive ferromagnetic disks at three values of the fixed excitation current. The research results show that the desired form of the mentioned characteristics of the SM is achieved only when using massive internal elements in the design of the IR. A separate figure shows the curves of changes in some values of the SM load, which will facilitate the development of methods for calculating the DB mode of the machine for the optimal design of the IR.

scholarly journals EXPERIMENTAL STUDY OF STATIC CHARACTERISTICS ASYNCHRONOUS MACHINE IN DYNAMIC BRAKING MODE WITH INDUCTION RESISTANCE IN THE ROTOR WINDING

2021 ◽  
Vol 1 (38) ◽  
pp. 68-74
Author(s):  
S. Kolychev ◽  
А. Sianov
Keyword(s):  
Induction Machine ◽  
Current Frequency ◽  
Asynchronous Machine ◽  
Phase Switching ◽  
Asynchronous Machines ◽  
Braking Torque ◽  
Supply Current ◽  
Control Circuits ◽  
Rotor Winding ◽  
Dynamic Braking

The article discusses the results of a study of the static electromechanical characteristics of an asynchronous machine (AM) when prototypes of induction resistances (IR) with improved parameters are included in its rotor circuits. The dynamic braking (DB) of asynchronous machines, which is widespread in practice, provides for the dissipation of the kinetic energy of the rotating parts in the resistance boxes included in the rotor winding. In the process of stopping, to maintain a constant average braking torque AM, a bulky relay-contactor circuit for shunting rotor resistances is used. However, it is not possible to eliminate significant fluctuations in the electromagnetic torque in this way. To optimize the DB AM process, it is proposed to include a three-phase  IR in the rotor winding instead of resistance boxes, the value of which automatically decreases along with the rotor current frequency. This approach allows you to abandon contact equipment and ensure smooth braking of the machine with fluctuations in the electromagnetic moment in narrower limits. The known IR designs are designed for starting modes of induction motors with a wound rotor, but they cannot ensure the constancy of the torque on the AM shaft in the DB mode. Therefore, the purpose of the study is to develop and experimentally confirm the effectiveness of simple control circuits of an induction machine in the specified mode with improved contactless induction rheostats in the rotor. The paper presents a diagram of a pilot plant and a figure explaining the design features of the IR. The studies were carried out for an asynchronous machine of the MTB-412-8 type, equipped with a thyristor exciter and a tachogenerator. The three phases of the AM rotor included ICs connected by a "star". The experiments were carried out in the direction of obtaining the necessary braking characteristics of the AM by varying the switching circuit of the stator phases and the value of the current supplying them. The figures show the mechanical characteristics of AM, obtained in the process of studying the influence on them of three typical circuits for switching on the phases of the stator winding and two values ​​of the fixed supply current. The research results show that the desired form of the mentioned AM characteristics is achieved only when using the stator phase switching in a function of the rotor speed and a constant supply current value.

Experimental studies on magnetorheological brake containing plane, holed and slotted discs

2017 ◽  
Vol 69 (2) ◽  
pp. 116-122 ◽  
Author(s):  
Chiranjit Sarkar ◽  
Harish Hirani
Keyword(s):  
Experimental Studies ◽  
State Condition ◽  
Frictional Torque ◽  
Iron Particles ◽  
Low Friction ◽  
Mr Fluid ◽  
Content Type ◽  
Shear Rates ◽  
Mr Fluids ◽  
Braking Torque

Purpose This study aims to design an ideal magnetorheological (MR) brake that exerts negligible frictional torque in the off-state condition and controllable frictional torque in the on-state condition. Design/methodology/approach Silicone-based MR fluid, containing 9 per cent volume carbonyl iron particles, has been synthesized and used. The synthesized MR fluid is advantageous in maintaining low friction losses in off-state conditions. A magneto-rheometer has been utilized to characterize the off-state viscosity of the MR fluid at variable shear rates and shear stress of MR fluids at various magnetic fields. A mechanism to enhance the braking torque in the on-state condition has been designed and developed. An experimental test rig has been developed to capture the torque characteristics of the developed MR brakes. Three different designs of MR discs have been experimented under a magnetic field varying from 0 to 375 kA/m. Experimental results of braking torque under shear and compression modes have been presented. Findings Slotted disc MR brake gives much better torque performance. Originality/value The braking torque results motivate to use the slotted disc MR brake for high torque application.

scholarly journals Numerical and experimental studies on a novel magneto-rheological fluid brake based on fluid–solid coupling

2019 ◽  
Vol 103 (1) ◽  
pp. 003685041987900 ◽  
Author(s):  
Shujun Li ◽  
Wenjun Meng ◽  
Yao Wang
Keyword(s):  
Heat Dissipation ◽  
Coupling Effect ◽  
Experimental Studies ◽  
Test System ◽  
Structure Design ◽  
Brake Disc ◽  
Braking Torque ◽  
Braking Process ◽  
Magneto Rheological ◽  
The Impact

The previous work of the authors indicated that the fluid–solid coupling effect of the magneto-rheological fluid and the brake disc is a necessary focus during braking process. In this study, a novel design of magneto-rheological fluid brake was proposed and studied theoretically and numerically, aiming to solve the prominent problem of heat dissipation, especially in the case of single emergency braking. First, based on the modified Bingham model, a parameter defined as the apparent equivalent viscosity was utilized to represent the relationship of magnetic field, flow field, and temperature field. The braking torque and the formula for calculating the impact factor of fluid–solid coupling employed for characterizing the associations among the thermal field and the stress field were established based on fluid–solid coupling. With a detailed explanation of simulation method, the distribution disciplinarian’s numerical simulation of each field was analyzed using COMSOL software. To validate the accuracy of the established model on the designed magneto-rheological fluid brake, the prototype was also manufactured, and results achieved experimentally which were measured on inertia test system of brake, for braking torque, motion parameters, and surface temperature in braking process, were compared with simulations. Simulation results manifested that the designed magneto-rheological fluid brake’s magnetic circuit structure is feasible based on magnetic induction intensity distribution. Finally, it has been shown that the simulations appear to be basically consistent with the experimental results, and the heat dissipation of the designed magneto-rheological fluid brake is partially improved. These results might contribute to the structure design, optimization, and improvement of magneto-rheological fluid products, extending the previous work on fluid–solid coupling analyses.

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