Political Satire cartoons on Gas rate hike in newspapers

An Introduction to Electrical Drives

Drives

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Principle of Operation of Transformer

Transformer

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Introduction to MATLAB

Matlab Mech Eee Lectures 1

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Principle of Operation of DC motor & Generator

Dc motors

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vector control of Induction motor drive

    In applications where high performance variable speed operation is required, only 

dc motors were extensively used due to the ease speed control. Separately excited dc 

motors were particularly popular in applications where fast torque response was required. 

However, dc motors have some generic disadvantages like, requirement of periodic 

maintenance. Unusable in explosive or corrosive environments due to sparking problem. 

Commutation is difficult at high currents and voltages and hence its use is limited to low 

power, low speed motors.

    These problems can be overcome by using induction motors, which have a simple 

and rugged structure. Further, they have a high torque weight ratio as compared to their 

dc counterparts.

    The field and the armature currents respectively can control the  flux and torque, 

independently in the case of dc motors. It is because of this inherent decoupling between 

the field flux and the armature current, one is able to achieve very good torque dynamics 

from dc machines. Unlike dc machines, there is no inherent decoupling between flux and 

torque producing components of the stator currents in the induction  machines. Therefore, 

achieving good torque dynamics in ac machines is not easy. However, nowadays, field 

oriented control or vector control techniques have been employed, which results in good 

torque dynamics of induction motors. 

    In this dissertation work all discussions relating to induction motors  are with 

respect to squirrel cage type induction motors only. The operation of the 3phase induction 

motor is based on Faraday’s law and Lorentz force on a conductor. According to 

Faraday’s law, if the flux linking a conductive loop varies as a function of time, then an 

e.m.f, which is proportional to the rate of change of flux, is induced in the loop there by 

forcing a current to flow in the conductive loop. In the case of induction  motor, the induced current in the rotor conductors interact with the air gap flux to produce the 

torque. As the rotor tries to catch up with the magnetic flux in accordance with the Lenz’s 

law, the rate at which conductors are cut by the magnetic flux is reduced. As a 

consequence the induced rotor currents decrease and the Lorentz force on the rotor 

conductors reduce. Evidently if the rotor conductors were to catch up with the magnetic 

flux then there would be no relative motion between the conductors and the flux, and this 

would result in zero rotor currents and zero torque. Therefore, for the induction motor to 

operate there must exist some relative speed between the flux and conductors, which is 

called the slip speed ωsl.
for more click here VECTOR CONTROL

Political Satire cartoon1

ayyarao's photostream on Flickr.

cartooinst sridhar known for his cartoons sketched one good political satire cartoon in eenadu newspaper dated 12th june 2011.

Support to Lokpal Bill

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