Electrical Engineering

What is Gain? Gain is a proportional value that shows the relationship between the magnitude of the input to the magnitude of the output signal at steady state. Many systems contain a method by which the gain can be altered, providing more or less "power" to the system. However, increasing gain or decreasing gain beyond a particular safety zone can cause the system to become unstable. Consider the given second-order system: We can include an arbitrary gain term, K in this system that will represent an amplification, or a power increase: In a state-space system, the gain term k can be inserted as follows: The gain term can also be inserted into other places in the system, and in those cases the equations will be slightly different.   Example: Gain Here are some good examples of arbitrary gain values being used in physical systems: Volume Knob On your stereo there is a volume knob that controls the gain of your amplifier circuit. Higher levels of v

Electrical Power By: W.J.R.H.Pooler  

 Electrical Shock Definition : Electrical Shock, a condition that occurs when there is a flow of electricity through the body. Causes of an electric shock: It is usually caused by contact with poorly insulated wires or ungrounded electrical equipment , by using electrical equipment while in contact with water, or by being struck by lightning. The severity and effects of electrical shock depend on:- 1- The amount of current passing through the body 2- Type of current "AC or Dc" 3- Skin Case "Wet or Dry" 4- The duration of contact Types of electrical shock:-   1- Small (1-8) mA => Not effect on the body 2- Medium (20-50) mA => Lead to difficulty in breathing 3- Large (50-100) mA => Lead to disturbances in the heart and may lead to death Protection against electrical shock:- 1- Grounding equipment and electrical devices. 2- The use of cables with good insulation and suitable cross section area. 3- Use of appropriate breaker

  Control Engineering Using Matlab  By: Derek P.Atherton

 Principles of Electronics  By- V.K. Mehta, Rohit Mehta  

Modern Power Electronics and Ac Drives Author : Bimal K. Bose

       Electric Power Substations Engineering                                                           By:  J.D. MacDonald                                                              Format: PDF

Logic-Computer-Design-Fundamentals  By- M.Morris Mano                                       

Electronic Materials and Devices By- S.O. Kasap 

Digital Signal Processing By-John G. Proakis Dimitris G. Manolakis

Modern Digital and Communication System By- B.P. Lathi

Elements of Electromagnetic By-Matthew n.o Sadiku  

" Power system stability is the ability of an electrical power system, for a given initial operational condition,to regain  a state of operating equilibrium after being subjected to a physical disturbance ,with most system variables bounded so that physically the entire system   remains intact "   P ower system engineering forms a vast and major portion of electrical engineering studies. It is mainly concerned with the production of electrical power and its transmission from the sending end to the receiving end as per consumer requirements, incurring minimum amount of losses. The power at the consumer end is often subjected to changes due to the variation of load or due to disturbances induced within the length of transmission line. For this reason the term power system stability is of utmost importance in this field, and is used to define the ability of the of the system to bring back its operation to steady state condition within minimum possible time after h

 

The voltage generated in the armature, placed in a rotating magnetic field , of a DC generator is alternating in nature. The commutation in DC machine or more specifically commutation in DC generator is the process in which generated alternating current in the armature winding of a dc machine is converted into direct current after going through the commutator and the stationary brushes. Again in DC Motor , the input DC is to be converted in alternating form in armature and that is also done through commutation in DC motor . This transformation of current from the rotating armature of a dc machine to the stationary brushes needs to maintain continuously moving contact between the commutator segments and the brushes. When the armature starts to rotate, then the coils situated under one pole (let it be N pole) rotates between a positive brush and its consecutive negative brush and the current flows through this coil is in a direction inward to the commutator se

What are the conditions when the poly phase (here three phase) induction machine will behave as an induction generator? The following are conditions when the induction machine will behave as an induction generator are written below: (a) Slip becomes negative due to this the rotor current and rotor emf attains negative value. (b) The prime mover torque becomes opposite to electric torque. Now let us discuss how we can achieve these conditions. Suppose that an induction machine is coupled with the prime mover whose speed can be controlled. If the speed of the prime mover is increased such that the slip becomes negative (i.e. speed of the prime mover becomes greater than the synchronous speed).Due to this, all the conditions that we have mentioned above will become fulfilled and machine will behave like an induction generator. Now if the speed of the prime mover is further increased such that it exceeds the negative maximum value of the torque produced then the generati

In the present article we are going to discuss one of the easiest methods of making the phasor diagram for synchronous generator . Now let us write the various notations for each quantity at one place, this will help us to understand the phasor diagram more clearly. In this phasor diagram we are going to use: E f which denotes excitation voltage V t which denotes terminal voltage I a which denotes the armature current θ which denotes the phase angle between V t and I a ᴪ which denotes the angle between the E f and I a δ which denotes the angle between the E f and V t r a which denotes the armature per phase resistance In order to draw the phasor diagram we will use V t as reference .Consider these two important points which are written below: (1) We already know that if a machine is working as a synchronous generator then direction of Ia will be in phase to that of the E f . (2) Phasor E f is always ahead of V t . These two points are necessary for making the

Before knowing about, winding factor , we should know about pitch factor and distribution factor , as winding factor is the product of pitch factor and distribution factor . If winding factor is denoted by K w , pitch factor and distribution factor are denoted by K p and K d respectively, then, k w = k p k d . The pitch factor and distribution factor are explained below one by one.   Pitch Factor In short pitched coil, the induced emf of two coil sides is vectorically added to get, resultant emf of the coil. In short pitched coil, the phase angle between the emfs induced in two opposite coil sides is less than 180° (electrical). But we known that, in full pitched coil, the phase angle between the emfs induced in two coil sides is exactly 180° (electrical). Hence, the resultant emf of a full pitched coil is just arithmetic sum of the emfs induced in both sides of the coil. We well know that, vector sum or phasor sum of two quantities, is always less than their arith

Power rating of alternator is defined as the power which can be delivered by an alternator safely and efficiently under some specific conditions. Increasing load, increases losses in alternator, which leads to temperature rise of the machine. The conductor and insulator parts of the machine have some specific over heating withstand limits. The power rating of an alternator is so specified, that at that maximum load, the temperature rise of different parts of the machine does not cross their specified safe limit. The copper losses i.e. I 2 R loss varies with armature current and core losses vary with voltage. The temperature rise or heating of alternator depends upon cumulative effect of copper losses and core losses. As there is no role of power factor upon these losses, the rating of alternator generally given in VA or KVA or MVA. In other word, as the losses of alternator are independent of electrical power factor , hence power factor does not come into picture

Cylindrical Rotor Type Alternator Construction wise, an alternator generally consists of field poles placed on the rotating fixture of the machine i.e. rotor as shown in the figure above. Once the rotor or the field poles are made to rotate in the presence of armature conductors housed on the stator, an alternating 3 φ voltage represented by aa’ bb’ cc’ is induced in the armature conductors thus resulting in the generation of 3φ electrical power. All modern day electrical power generating station use this technology for generation of 3φ power, and as a result the alternator or synchronous generator has become a subject of great importance and interest for power engineers of late. An alternator is basically a type of a.c generator also known as synchronous generator , for the simple reason that the field poles are made to rotate at synchronous speed N s = 120 f/P for effective power generation. Where f signifies the alternating current frequency and the P represent

The working principle of alternator is very simple. It is just like basic principle of DC generator. It also depends upon Faraday’s law of electromagnetic induction which says the current is induced in the conductor inside a magnetic field when there is a relative motion between that conductor and the magnetic field. For understanding working of alternator let’s think about a single rectangular turn placed in between two opposite magnetic pole as shown above. Say this single turn loop ABCD can rotate against axis a-b. Suppose this loop starts rotating clockwise. After 90° rotation the side AB or conductor AB of the loop comes in front of S-pole and conductor CD comes in front of N-pole. At this position the tangential motion of the conductor AB is just perpendicular to the magnetic flux lines from N to S pole. Hence rate of flux cutting by the conductor AB is maximum here and for that flux cutting there will be an induced current in the conductor AB and direction o