Interfacing dataTaker

Ever wondered how remote controlling of a large number of instruments work in a given scenario of a big experimental set up such as superconductivity testing or missile launching where a large number of devices need to be handled simultaneously, with very less supply dedicated for it? Standardized protocol and data formats to log data play a very crucial role in addressing these scenarios. One of the pioneer tool in this field is dataTaker. 

-project and article contributed by Adil Wankhede, VNIT, Nagpur. 

Rubber bands- they can be stretched by our hands. Ever wondered how other materials such iron, copper, superconductors etc. could be stretched? A universal testing machine (UTM), also known as a universal tester, materials testing machine or materials test frame, is used to test the tensile strength and compressive strength of materials. The "universal" part of the name reflects that it can perform many standard tensile and compression tests on materials, components, and structures.

-project and article contributed by Shantanu Bhosale, EEE, VNIT, Nagpur.

About Mahindra and Mahindra’s Farm Equipment Division-

Mahindra & Mahindra’s Farm Equipment division is the top-selling tractor company in the world, with annual sales over 150,000, a presence in more than 40 countries and more than 1,000 dealers worldwide.  They manufacture tractors at four state-of-the-art plants in India, two in China, three in the US, and one in Australia, grounding us in four major agricultural hubs to give us close on-the-ground understanding of what farmers need from their tractors.  Their strong R&D team of more than 600 engineers constantly push technology forward.

State Estimation:

It is a process where the state of the power system is estimated.All the telemetry values of power flow, voltage levels are considered.These values are used to calculate the phase angle of the voltage which helps in determination of the power flow between two nodes in the power system as the power flow is directly proportional to sine of that angle.

The power flow monitoring is important for the power system as any kind of overloading on the lines can lead to cascade tripping and can also lead to black out.

Right from the beginning of commercial and domestic use of electricity, the generation has always been centralized in a massive capacity. We have always depended on the power plants to generate all of the electricity that we used. Our Grid is built to serve the basic purpose of delivering the electricity generated at the doorstep of consumers. But the paradigm of the power system is going to be shifted as we, as individuals, villages, towns, states, countries are becoming more and more conscious about our carbon footprint on the world we live in.

 The Paris Treaty on Climate Change dealing with the green-house gasses emission mitigation, adaptation and financing has been signed by 161 nations within the UNFCCC (United Nations Framework Convention on Climate Change) as of October 2016.

SolarEdge, Israel based company has definitely sensationalized the PV inverter market with HD wave technology claiming to double the power density delivered compared to traditional pv-inverters. What is this technology? Did it exist previously? If it did, what stopped it from being commercialized? How will it revolutionize the inverter market? Endless number of questions have flooded the internet. This post is an answer to these questions in a nutshell.

Introduction

A strobe light or stroboscopic lamp, commonly called a strobe is a device used to produce regular flashes of light. It is one a number of devices that can be used as a stroboscope. A typical commercial strobe light has a flash energy in the region of 10 to 150 joules, and discharge times as short as a few milliseconds, often resulting in a flash power of several kilowatts. Larger strobe lights can be used in “continuous” mode, producing extremely intense illumination.

" press 1 for balance
press 2 for internet plans
..."
Aren't these lines familiar? In fact they are. These  are the lines of the  automated voice which guides you when you call the service number of your mobile operator.
Ever it crossed your mind how they are able to know which button has been pressed?

Even after getting acquainted to the various concepts related to electrical engineering, there is always one important concept which most electrical engineers, including me, tend to forget. What exactly is reactive power? What is power factor? Why is it so damn important? What do you actually mean by lag and lead? So this discussion would be an informative recap into the basics.

Disclaimer: You could find this highly descriptive, but a short circuit is the only thing ‘short’ in Electrical Engineering. :P

Nikola Tesla set his foot on the land of New York, America on 6th June 1884 with 4 cents and a dream to manufacture his alternating current motor. He also had a letter of recommendation from Charles Batchelor to Edison. Edison was among one of the few men capable of helping Tesla manufacture his motor at that time.

India has one of largest electrical networks in the world. Different types of sources and load are feeding and consuming power from this massive mesh called the NATIONAL GRID. All the sources are connected in parallel. Parallel operation of the generators improves the reliability of the power system by allowing the isolation of few generators for maintenance or under fault condition without any loss of load.

Maximum percentage of power generation is done by Coal based and hydro-based power plants which use synchronous generators as the generating unit. Wouldn't it be interesting to understand how these power plants control the flow of power and maintain such a large network where there is so much variation of load time to time. Let’s become adept over it.

To begin with lets analyze two synchronous generators working in parallel and observe how various circuit parameters are affected. There are two ways how the generating unit control the power flow to the grid:

•  Adjusting the Driving Torque
• Adjusting the Excitation Voltage

In this post we shall discuss just the affect of change of driving torque on various parameters.

NO LOAD OPERATION:

Let us consider two alternators connected in parallel and are unloaded. With respect to external circuit, both the emfs of generators are in phase and with respect to the local circuit they are in phase opposition.

   

Driving torque can be varied by controlling the gate openings of the hydro turbines or by throttle openings of steam turbine. In this article, we have considered cylindrical rotor generator but the results are equally relevant to salient pole generator too.          

If we increase the driving torque of generator 1, then speed increases and generator 1 emf (E_f1)  gets ahead of generator 2 emf (E_f2) there by a resultant emf (E_c) appears. Due to this resultant emf, E_c a circulating current I_c (fig i) flows which lags E_c by almost 90^.  (as the value of resistance is too small compared to the reactance of the machine). This current flows out of gen 1 nearly in phase with it’s emf E_f1 and enters gen 2 in near phase opposition with E_f2. Thus Gen 1 produces power (=E_f1I_c) as a generator and supplies it to Gen 2  which acts as a motor. This would thus retard the faster machine and accelerates the slower one, finally leading to auto equalization of speed.
  

It is necessary that the machines impedance shouldn’t be purely resistive. If they are purely resistive, then the circulating current would be in phase with E_c      (fig ii) and thereby both will act as generator. There would be no tendency of auto equalization of speed. It implies that there would be frequency mismatch leading to power surges and harmonics.

ON LOAD:

The load current I_L = I_a1 + I_a2 (can be seen in the circuit beside).  Increasing the driving torque would result a change in the amount of load shared, the currents I_a1 and I_a2 and respective power factors. Howsoever, the load current I_L remains constant. First, we’ll see how load sharing varies.
On load operation depends upon the speed-load characteristics of the alternator. Generally these characteristics are not linear. Hence a governor mechanism is used to make them linear as in the figure beside.

If we increase the driving torque of Gen1, speed increases and the speed-load curve shifts upwards indicating the increase in speed. Obviously decreasing the driving torque would shift the characteristics downwards. 

Consider the two generators are supplying to a load P_L (=P₁+P₂ initially). Now if we increase the driving torque of gen1. It’s speed-load characteristics shift upwards. In order to maintain the frequency (as the load is constant) the driving torque of gen2 should be decreased. Thus the dotted lines in the figure indicate the speed load characteristics of both the generators and the line2 indicates the frequency of the constant load. Thus the load shared by gen1 increases to P₁’ and the load of gen 2 decreases to P₂’ but to the end the sums of loads shared by both the generators would be constant and equal to the total load P_L.
Now let us see how the currents and power factors of each generator is effected.

At first assume that E_f1= E_f2 and therefore Ia₁=Ia₂ and the load shared will be equal.

Now increase the driving torque of gen 1 which increases the speed and frequency and thereby increasing the power angle δ to δ1 and the power increases to P₁’.

                                     

 The driving torque of gen2 is now decreases in order to supply to the load at constant frequency. E_f2 decreases and power angle also decreases to δ2 and the power decreases to P₂’.

More over, this change in the emfs will lead to a resultant emf E_c. Hence,  a circulating current flows which lags E_c almost 90^.. This current adds up to I_a1 and hence current through gen 1 increases (indicating that the load shared by this gen has increased). The power factor angle decreases thereby improving the power factor. The current I_c reduces the current from gen 2 and there by indicating that the load shared by this gen is reduced. The power factor angle increases and thereby decreasing the power factor.

Thus we can conclude that, by increasing the driving torque on load increases the load shared, current and also improves the power factor.

Electricity is the present era’s OXYGEN. How restless we grow when there is a power cut in summer nights especially when we are about to go to bed, or having our dinner, watching TV or having exam the next day! Well these have become a matter of past as INVERTERS have protruded the whole market. Although last institutes, hospital and other large load rely on DG set, inverters have captured almost every home.

Won’t it be interesting to begin designing our own inverter? So let’s get started!!

As a VNITian, you guys might have observed that VNIT stands out from Nagpur city when it comes to power cut. Power cuts are rare and even when there is a power failure due to some fault we have supply for our mess and in exam time in our hostel even. Wouldn’t it be interesting to know how the electrical distribution and substations our college are configured meets the demand of uninterrupted supply? Let’s find out!

Potier triangle method is helpful in obtaining the voltage regulation of synchronous machines. It gives the value of potier reactance and the armature mmf (reaction) by drawing a series of curves on experimental basis.

Potier reactance is the air gap reactance (leakage reactance) of the synchronous machine at full load (rated voltage and current of armature).

Circuit Diagram For Determination of Portier Reactance

Working of Analog Clock

Importance of time keeping is recognized ever since the life came into existence. From just days and nights demarcating the time to using sundials for time keeping in the days in medieval period to balanced wheels and pendulum clocks in 15 and 16^th century, time keeping had always remained a challenge to the scientists.

  

The first electric clock was patented in 1840 and since then there has been a lot of advancement in this sphere. Digital Clocks have capture the 21^st century world however analog clocks still remains a part of almost all the houses.

This post is dedicated to explaining the working of these analog clocks.

  

SAIL AT A GLANCE

Steel Authority of India Limited is India’s largest steel producing company and ranks 24th in the World. It was founded in 19th January 1954 with headquarter at New Delhi. It was incorporated to central public sector on 24 January 1973.  With an annual turnover of Rs. 49350 crore, the company is among the seven Maharatnas of the country’s Central Public Sector Enterprises.