EPM 202 Lecture 1 PDF

Introduction  Introduction Electric machines are employed in almost every industrial and manufacturing process. Pages can be filed in listing the applications of electric machines right from giant-size generators (500 MW and above), industrial motors ranging up to a few megawa...

Introduction  Introduction Electric machines are employed in almost every industrial and manufacturing process. Pages can be filed in listing the applications of electric machines right from giant-size generators (500 MW and above), industrial motors ranging up to a few megawatts to fractional-kW domestic appliances and to sophisticated aerospace applications requiring stringent reliability in operation.  Electric Machines Electricity does not occur naturally in usable form, and it also cannot be stored in usefully large quantities. Therefore, it must be generated continuously to meet the demand (of power) at all times. An efficient and convenient way to generate electric power is by conversion of mechanical power into electrical form in a rotating device called a generator. In the process a small part of power is lost in the generator (efficiencies in large generators are above 90%). The mechanical power is itself obtained from heat power by thermodynamical means in a steam turbine (efficiency in the range of 40–50% as the present upper limit) or by conversion of potential energy of water in a hydraulic turbine with very little loss. The basic source of mechanical power—steam/hydraulic turbine is called the prime mover. Electro-mechanical Energy Conversion Devices Electro-mechanical Energy Conversion Devices Electro-mechanical Energy Conversion Devices Electro-mechanical Energy Conversion Devices  Transformer A transformer is a static device that transfers AC electrical power from one circuit to the other at the same frequency, but the voltage level is usually changed. It is this device that has made the electric system almost universally ac. The electric power is generated at relatively low voltages (up to a maximum of 33 kV) which then is raised to very high voltages (e.g. 756 kV) by means of a transformer and then transmitted. High voltages are associated with low currents and reduced transmission losses. Geographically close to the use points, the electric power is transformed back to safe low utility voltages (380/220 V). Section 1-1 Checkup Basic Principle, types and Constructional Features of Electric Machines  Basic Principle, types and Constructional Features of Electric Machines imp. Basic Principle, types and Constructional Features of Electric Machines