Wyniki wyszukiwania - BazTech

1

Modelling the Effects of Residual Stresses on Electro-Magnetic Properties of Super Alloys

Goetz S., Chandra D., Veselova D., Klocke F.

Journal of Machine Engineering

|

2015

|

Vol. 15, No. 3

33--40

EN

Super Alloys, commonly used in safety-critical aerospace components, regularly impose problems when machined in drilling or milling processes, resulting in surface damages that facilitate cracks. Residual stresses are often induced to prevent crack mitigation, but national aviation agencies set high quality standards on them. Current methods are either destructive or impose safety risks for the employees. Eddy current methods, however, are fast and cheap non-destructive methods to receive information on metallic surfaces. They rely on electro-magnetic properties of the material. The influence of residual stresses on both permeability and conductivity are not yet fully understood. This article presents a simple model that describes the correlation between residual stresses and those aspects. At first, the dependency of permeability and conductivity on various metallurgical properties, such as grain size or orientation, is deduced. In a second step, the influence of residual stresses on these properties is shown. A third step combines both steps into a coherent and holistic model to describe the influence of residual stresses on the electro-magnetic properties of Super Alloys. This model will help establishing Eddy Current Testing in the product monitoring in the aerospace industry.

2

Vector Controlled Induction Motor Drive Using Genetic Algorithm Tuned PI Speed Controller

Dey A., Singh B., Dwivedi B., Chandra D.

Electrical Power Quality and Utilisation. Journal

|

2009

|

Vol. 15, iss. 1

3--8

EN

In (his paper, timing and optimization of the proportional and integral (PI) gains of speed controller is achieved using Genetic Algorithm (GA) for improving the performance of the induction motor drive because higher the quality of the controller lesser is the ripples produced in the torque and speed responses. The developed GA program has multi-objective minimization functions. The optimized values of PI gains are incorporated in vector controlled induction motor model for performance analysis during sudden disturbances like speed reversal, load application and load removal. GA tuning method outstandingly surpasses the conventional and most widely used Ztegler Nichols Tuning method. GA tuned PI controller reduces the peak overshoot almost by 60% and quickly brings the system to steady state value. The simulated results obtained from GA tuned PI controller can be realized and validated through experimental results in future work.

3

An improved model of a three phase induction motor incorporating the parameter variations

Dey A., Tripathi A., Singh B., Dwivedi B., Chandra D.

Electrical Power Quality and Utilisation. Journal

|

2008

|

Vol. 14, iss. 1

73--78

EN

A great deal of work is being done on the betterment of control through simulation of the electric drives used for various high-power purposes. The authenticity of the simulated results is based on the accurate modeling of the various parts of the electric drive system. Three–phase Induction motors form an extremely important part of the modern day electric drive system and their usage is continuously on a rise owing to their inherent properties of ruggedness, minimum maintenance requirements and continually increasing efficiencies. Usually the three-phase Induction motor model used in various research works does not incorporate stator and rotor core losses, stator and rotor stray load losses and magnetizing saturation and rotor conductor skin effects. The present paper aims at developing a threephase Induction motor model taking the above losses and effects into account. The dynamic linking of the model to a thermal model considering the temperature dependent resistive elements is an added feature. The motor model described in this paper is the extension of the conventional 2-phase lumped-parameter induction motor model. The biggest advantage is that the model is user-programmable in MA TLAB environment and can be used for system level transient studies. The simulation results of the developed model, with various parameter variations taken into account and subjected to sudden changes in load, show better torque and speed performances of the motor both in steady state and dynamic conditions.

4

A new closed loop speed control strategy for a vector controlled three-phase induction motor drive

Tripathi A., Dey A., Dwivedi B., Singh B., Chandra D.

Electrical Power Quality and Utilisation. Journal

|

2008

|

Vol. 14, iss. 1

67--72

EN

This paper presents a completely mathematical equations based model on control of torque and speed of a three-phase indirect vector controlled VSI fed cage induction motor drive that is controlled through the space vector modulated method. This enables a wide range of acceptability of the model for various values of load and for various types and ratings of induction motors. The uniqueness of the model lies in the fact that the deviations in the torque and speed on sudden application of reference step change in speed values are minimum i.e. when any sudden change in the speed reference is desired, the speed and torque waveforms reveal that the time taken in coming back to their final steady state values is very less and the motor overcomes the perturbation with negligible transients. The same is verified through the simulated results.