Nirmal K. Deb

Design and Performance of a Single Stator, Dual Rotor Induction Motor

This paper presents the design and performance of a motor having two rotors along the same axis and under the span of a single stator. This special type of motor has two shafts projecting from the two ends, which are mechanically independent of each other and thus can meet the requirement of differential drive in an electrical vehicle. This paper presents the design, construction and performance data obtained from experimental results of the motor. An equivalent circuit of the motor has been developed and verified. The characteristics of the dual rotor motor have been obtained experimentally from a prototype and presented in this paper.

Efficiency and Cost Optimized Design of an Induction Motor Using Genetic Algorithm

In the context of electricity shortage and an attempt to save the environment, introduction of energy efficient motors in different fields of application has become a necessity. This paves the way for fusing the conventional machine design procedures with optimization techniques. Unfortunately, the mathematics of electrical machine design involves calculations with highly nonlinear equation sets, and hence the conventional analytical optimization techniques do not fit well. In this study, design of an efficiency-optimized squirrel cage induction motor is considered, where genetic algorithm is chosen as the tool for optimization. The various constraints considered are selected on the basis of material, mechanical, and performance considerations as approved by standards and practices. The influence of change of materials and change of upper limit of customers budget on different key motor design performance indicators are studied with and without cost constraints. Also, a systematic and statistics-based approach is proposed to achieve an optimized motor design, even at very low cost, provided relaxation of some constraints is allowed by the specific application. The optimized results are validated through tests on laboratory prototypes.

Chopping off peak demand using DLS technique — Formulating an intelligent technique for load identification

This paper identifies electrical load which are brought under DLS technique in order to use effectively for judicious scheduling of loads for chopping off peak load demand. In general an analysis is made on loads, their type, and to suggest how to schedule these loads for an entire day and thereby chopping the peak load demand. The present paper approaches for a problem formulation which helps in timely decision making for those who will be using this technique for chopping peak load demand. This paper analyses on different loads and thereafter gives a decision for those loads that are to be included for DLS technique application and hence reduce the peak demand on a very short span of time. The entire decision making technique is governed by Artificial Intelligent method. This method helps in reduction of peak demand.

Selection of the Filter Capacitor for Power Supplies using 1-Phase Diode Rectifier

Diode bridge rectifiers with capacitor-input filters are commonly used at the input stage for power supplies operating from the single phase mains input, as they provide a cost effective solution in the lower power range. However, as there is no simple design rule existing in published literature that gives a reasonable prediction based on real-life conditions, the design of the rectifier-capacitor stage is still a trial and error or based upon experience. This paper presents an approximate (but simple) solution based upon empirical relations, for the prediction of the currents involved and specifies the capacitor, so that it can be selected.

Dual Delta Bank TCR for Harmonic Reduction in Three-Phase Static Var Controllers

The conventional “Delta” connected thyristor-controlled reactor (TCR) bank used for static var compensation and other applications is proposed to be split into two identical “Delta” banks each having kvar capacity half of the total TCR capacity. The study presented shows that such combination of two identical “Delta” connected reactor banks, one with phase switching by thyristors and the other with line switching thyristor arrangement can effectively reduce the harmonic generation of the TCR. Since both the three-phase banks are connected in delta, the zero sequence triplen harmonics generated due to phase control of thyristors remain trapped inside the delta, thus reducing the harmonic injection into the power system. Further, some other major characteristic harmonics are also minimized in the TCR line current. Thus, the proposed TCR yields a low current THD which meets the requisite harmonics standards and it can therefore be used as an economic solution for reactive power control over a reasonable range in high power grid without using any external harmonic filter or special phase shifting transformer. This paper describes in detail the modeling, analysis, and performance assessment of the proposed scheme. Simulation results are furnished to evaluate the output characteristics of the scheme under varying operating conditions. Finally, experimental results are presented, which proves the theoretical proposition.

Harmonic Cancellation in a Three-Phase Thyristor Controlled Reactor Using Dual Banks

A three-phase three-wire thyristor controlled reactor (TCR) topology is presented comprising of two reactor banks, involving simultaneous firing angle control of both banks having maximum kVAr in the ratio of 60:40. The first reactor bank is “Δ” connected and has phase switching whereas the second reactor bank is either “Δ” or equivalent “Y” connected with line switching. Such an arrangement prevents the triplen harmonics from entering into the supply system and some major characteristic harmonics can also be eliminated from the TCR line current due to the selection of the ratings of the two reactor banks. Thus, without using any additional filters or phase shifting transformer, this scheme enables reactive power control with a low current total harmonic distortion (THD) over a reasonable range of control, meeting requisite harmonics standards. Simplicity in construction and operational requirements of the proposed topology makes it a viable and cost effective solution. Its modeling, analysis, and performance assessment are presented. Simulation and experimental results support the theoretical proposition.

A New Harmonic Reduced Three-Phase Thyristor-Controlled Reactor for Static VAr Compensators

A new thyristor-controlled reactor scheme is presented in this paper, in which the total bank is split into one Δ- and one Y-connected reactor bank with the addition of a low-rating zig-zag autotransformer, instead of the conventional scheme using a Δ-connected reactor bank with a harmonic current filter. This arrangement prevents the triplen harmonics generated by the Y bank from entering into the supply system and at the same time, the combination results in cancellation of some major characteristic harmonics from the source current. Thus, without using any additional filters or phase-shifting two-winding transformer, this scheme facilitates reactive power control over a wide range and also meets the requisite harmonics standards. The scheme is simple and provides a cost-effective solution to the VAr compensation problem. Simulation and experimental results are provided to validate the proposed concept.

Commutation diagnosis in converter fed commutator motors from study of brush surface

Power converter-fed commutator motors have widespread use in the form of DC motors operating from rectifier or DC chopper supplies. Various nonideal operating conditions affect the proper commutation of current in the armature coils, thereby degrading the motor performance. Thus, in order to establish the nature of commutation of the machine and caution against impending failure, it is convenient to maintain a periodic check of the brush surface. This paper presents both a theoretical discussion and data from field experience to provide a primary basis for a novel approach by which commutation diagnosis may be made from studies of the motors brush surface.