Transmission Circuits

The heart of any utility power-distribution system is the cable used to tie distant parts of the network together. Conductors are rated by the American Wire Gauge (AWG) scale. The smallest is no. 36, and the largest is no. 0000. There are 40 sizes in between. Sizes larger than no. 0000 AWG are specified in thousand circular

steam generator

The steam generator has three major systems:

 -  Fuel system :

Fuel is mixed with air and injected into the furnace through burners. The burners are equipped with nozzles,

Fossil Fuel Power Plants

The most frequently used fuels for large-scale power generation are oil, natural gas,and coal. Figure 1.33 illustrates the principal elements of a fossil fuel power plant. Fuel handling includes transport by rail, on ships, or through pipelines. A power plant usually maintains several days of fuel reserve at any one time. Oil and gas

Power Generating Systems

Electrical power can be produced in many ways, including chemical reactions, heat, light, or mechanical energy. Most electrical power produced today is through hydroelectric plants, nuclear energy, and by burning coal, oil, or natural gas. Fossil fuel and nuclear-fission plants use steam turbines to deliver the mechanical

Power Generation

Any ac power system begins with a generating source. Electric generators are devices that convert energy from a mechanical form into an electrical form. This process, known as electromechanical energy conversion , involves magnetic fields that act as an intermediate medium. The input to the generating machine can be

Basic Principles

In 1831, English physicist Michael Faraday demonstrated the phenomenon of electromagnetic induction. The concept is best understood in terms of lines of force, a convention Faraday introduced to describe the direction and strength of a magnetic field. The lines of force for the field generated by a current in a loop of

Power Transformers

The transformer forms the basis of all ac power-distribution systems. In the most basic definition, a transformer is a device that magnetically links two or more circuits for time-varying voltage and current. Magnetic coupling has a number of intrinsic advantages, including:

Elements of the AC Power System

The process of generating, distributing, and controlling the large amounts of power required for a municipality or geographic area is highly complex. However, each system, regardless of its complexity, is composed of the same basic elements with the same basic goal: Deliver ac power where it is needed by customers. The

INDUCTION MOTOR MODEL

A dynamic model of the machine subjected to control must be known in order to understand and design vector controlled drives. Due to the fact that every good control has to face any possible change of the plant, it could be said that the dynamic model of the machine could be just a good approximation of the real plant.

Indirect vector control

Despite the strong incentives such as the absence of transducers and wide speed range operation, acceptance of the flux feedforward technique has been slow due to its dependence on the rotor parameters. With the advent of various parameter adaptation schemes to alleviate this problem, it has gained more attention and is

Direct vector control

The direct measurement technique was popular in the earlier stages due to the sensitivity of the estimation techniques to motor parameter variations.This technique also provided instantaneous and well damped control of torque. The earlier forms of this type of control involved the measurement of the air-gap flux. 

Classification

Two vector control strategies were formulated during the late 60's and decoupling of the stator currents was achieved either by direct measurement of the flux or by estimation from the motor model.Both these methods are based on the space phasor modeling of the induction machines The measurement technique is also known

Previous Research Works

The complexity of the control associated with the induction machines was alleviated by the advent of vector control in the early 70's .The main difference between vector control and the existing schemes for induction machines, such as the constant volts/Hz or slip frequency control, is that the frequency and voltage or current imposed on the motor are controlled without neglecting the phase relationships.Without appropriate phase angle control, vector control degenerates into conventional slip frequency control resulting in poor dynamic characteristics.Vector control was compared with the slip frequency control and found to have a faster torque response Quick torque response is achieved even if a load is applied and the drive system reaches steady state instantaneously. A comparative study of vector control with the torque angle control and synchronous control has been performed and the advantages of vector control highlighted.Vector control is also known as decoupling control since the stator currents are decoupled into separate torque and flux producing channels. It is also known as field oriented control due to the fact that the control is based on the field orientation of stator currents.

Vector Controlled Induction Motor Drives

The reason that DC motors have high performance in motion control is that a separately exited DC motor permits the separate control of torque and flux. The linearity of the system makes a DC motor easier to control than an AC motor. However, the mechanical commutation of the DC machine causes higher failure

Field oriented control

Field-oriented control provides the advantages of smooth motion at slow speeds as well as the efficient operation at high speeds.In many motor drive systems, it is desirable to make the drive act as a torque transducer wherein the electromagnetic torque can nearly instantaneously be made equal to a torque command.

Constant slip-speed control

In constant slip-speed control, the drive system is designed so as to accept a torque command input and hence the system demands an additional feedback loop requiring the use of speed sensor. The method is highly robust with respect to changes in machine parameters and results in high efficiency of both the machine

Constant volts/Hz control

The constant volts/Hz control is primarily designed to accommodate variable speed commands by using the inverter to apply a voltage of correct magnitude and frequency so as to approximately achieve commanded speed without the use of speed feedback. Therefore, it is safe to say that the simplest and the least expensive

Speed control

For the inverter-driven induction motor, the speed control is effectively achieved by means of variable frequency. However, apart from the frequency, the applied voltage also needs be varied so that the air gap flux can be maintained at a constant value without letting it to saturate. It is well known that in order to maintain the

Static frequency changers

The static frequency changers can be broadly classified as Direct and Indirect static frequency changers. The direct frequency changers are some times called as Cycloconverters. These convert the AC supply source frequency to a variable frequency. The input frequency ratio typically ranges from 0 to 0.5 and for the better

Induction Motor Control

The speed of an induction motor is very near to its synchronous speed. The difference between the two being characterized by the slip speed. If the synchronous speed of the induction motor is changed, there is a corresponding change in the speed of the motor and this can be done by changing the supply frequency of the