Tricky but Easy Electrical Engineering!
Pole changing method is a speed control scheme of induction motor. In this scheme, the number of pole pairs is changed by changing the field connection. In induction motor, field winding is wound on the stator while the armature winding is wound on the rotor. Therefore in this scheme, provision for changing the stator winding … Read more
Before going into the phasor diagram of transformer, there are some important points which must be kept in mind. Based on these points, we will draw the phasor diagram for No Load, Lagging Load and Leading Load condition of transformer. Important Points for Phasor Diagram of Transformer: 1) Transformer when excited at no load, only … Read more
There are mainly two types of induction motor on the basis of power supply, Single Phase Induction Motor and Three Phase Induction Motor. As their name suggests, 1 phase AC power supply is extended to single phase induction motor while three phase induction motor is connected to 3 phase AC power supply. Types of Single … Read more
Alternator or generator armature winding is always connected in STAR not in DELTA. We know that rotating magnetic filed in the air gap can only be created if the phase winding and phase currents are 120º displaced from each other in the space and time respectively. This can be achieved either in star connection or delta … Read more
We know that the very basic purpose of Transformer is to transmit power at two different voltage levels. For example, if a generating station is generating electrical power at 21 kV and evacuates it power at 400 kV then a three phase transformer of voltage rating 21 kV / 400 kV is used. But the … Read more
All Day Efficiency is defined as the ratio of total energy output for 24 hrs i.e. for the whole day to the total energy input for the same day. All Day Efficiency is basically Energy Efficiency of Transformer calculated for a period of 24 hrs. Mathematically we can write, All Day Efficiency = 1 – … Read more
Torque Slip Characteristics is the graphical relationship between the torque and slip of an Induction Machine. This characteristic is very useful for the stability analysis of the machine. Electromagnetic torque in an Induction Machine is given as Te = [Kx(r2/s)] / [(Re + r2/s)2 + X2] …………………(1) Where K = Constant From the above equation, … Read more
We are well aware of the fact that electrical machine core is made up of laminated sheets. This is done to reduce the eddy current loss. But how laminated core reduces the eddy current loss and what is the relation between the Eddy Current Loss and thickness of lamination? Let us consider an electrical machine … Read more
Excitation system in a Generator is essential for the production of working magnetic flux in the air gap. It is usually provided by having filed winding on the rotor in case of Synchronous Generator. Providing field winding on the rotor possess certain advantages over field winding on the stator (Read Why Armature Winding on Stator … Read more
Generator Compounding Characteristics is a curve depicting the variation of field current required to maintain a constant generator terminal voltage. Generator terminal voltage is maintained constant by controlling its field current either manually or by Automatic Voltage Regulator (AVR). Let us consider the phasor relation between the excitation voltage Ef and terminal voltage Vt for … Read more