[...]... based on the distance 12 Practical Troubleshooting of Electrical Equipment and Control Circuits and quantum of power Distribution circuits where typically the amount of power and distance involved are both lower, the best voltage is in the MV range (11, 22 or 33 kV) For the same reason, low voltage circuits are found only in local sub-distribution circuits 1.2 Basic principles of electrical machines 1.2.1... following chapters as and when required 2 Devices, symbols, and circuits Objectives • To understand basic electrical symbols • To understand power and control circuits • To read electrical drawings 2.1 Devices and symbols Any electrical drawing representing an electrical installation or a circuit takes the help of specific symbols to represent various electrical devices in shorthand This provides a... on the ratio of the number of turns in the primary and the secondary windings of the transformer 4 Practical Troubleshooting of Electrical Equipment and Control Circuits φ Iφ + – + N2 N1 V1 – E1 – – E2 P S + V2 Z + Figure 1.1 Schematic diagram of a single-phase transformer Potential-induced There is a very simple and straight relationship between the potential across the primary coil and the potential... wound-rotor M Figure 2.1 Electrical devices and symbols Generator M ~ Three-phase star–star transformer Motor Three-phase induction motor cage delta-connected 26 Practical Troubleshooting of Electrical Equipment and Control Circuits Power circuits have to carry heavy power and therefore, they consist of heavy conductors along with contactors used for switching the power on and off Protection devices... installation, and is particularly useful while troubleshooting Therefore, it is important to familiarize oneself with various symbols Some of the commonly used device symbols are detailed in the following section and in Figure 2.1 2.2 Electrical circuits Electrical circuits are circuits used to interconnect different electrical equipments together to enable the working of an electrical device Electrical. .. rules: The right hand rule Hold the conductor in the right hand with the fingers closed around the conductor and the thumb pointing towards in the direction of the current The fingers will point towards the direction of the magnetic lines of the flux produced around the conductor 14 Practical Troubleshooting of Electrical Equipment and Control Circuits Flux produced by a current-carrying coil Flux can...2 Practical Troubleshooting of Electrical Equipment and Control Circuits Voltage is defined as the electrical potential difference that causes electrons to flow Current is defined as the flow of electrons and is measured in amperes Resistance is defined as the opposition to the flow of electrons and is measured in ohms All three are bound together... the various types of connections of three-phase transformers On the primary side, V is the line voltage and I the line current The secondary sideline voltages and currents are determined by considering the ratio of the number of turns per phase (a = N1/N2) and the type of connection Table 1.1 gives a quick view of primary-line voltages and line currents and secondary-phase voltages and currents The... defines the relationship between the direction of the current, the direction of field, and the direction of the motion If the forefinger of the left hand points in the direction of the field, the middle finger points in the direction of the current, and the thumb points in the direction of the motion 1.2.3 The basic principle of motor The basic working of a motor is based on the fact that when ‘a current... direction and produces a field corresponding to the north and south polarities Maximum flux is along the center of the pole and reduces to zero between the interpole gaps 16 Practical Troubleshooting of Electrical Equipment and Control Circuits Rotor core Stator core Frame Stator winding Rotor winding Shaft Bearing Figure 1.10 Common features of an ideal electric machine N Gen Motor S S N (a) N S N . the accuracy and integrity of this document Date: 2005.05.26 06:18:45 +08'00' Preface i Practical Troubleshooting of Electrical Equipment and Control Circuits. large gap between the theory of electron flow, magnetic fields and that of troubleshooting electrical equipment and control circuits in the plant. In this