An Introduction to Text A Electric Machinery almost all tools.Of course,generators are necessary to supply the power used by all these motors. Transformers 2 A transformer is a device that changes AC electric power at one voltage level to AC electric power at another voltage level through the action of a magnetic field It consists of two or more coils of wire wrapped around a common ferromagnetic core.These coils are(usually)not directly connected.The only connection between the coils is the common magnetic flux present within the core. In a modem power system,electric power is generated at voltages of 12 to25 kV.Transformers step up the voltage to between 110 kV and nearly 1000 kV for transmission over long distances at very low losses.Transformers then step down the voltage to the 12-to 34.5-kV range for local distribution and finally permit the power to be used safely in homes,offices,and factories at voltages as low as 120 V. AC machinery fundamentals 4AC machines are generators that convert mechanical energy to AC electrical energy and motors that convert AC electrical energy to mechanical energy.The fundamental principles of AC machines are very simple,but unfortunately, they are somewhat obscured by the complicated construction of real machines There are two major classes of AC machines-synchronous machines and induction machines.Synchronous machines are motors and generators whose magnetic field current is supplied by a separate DCpower source,while Unit 2 Electric Machinery and Electrical Equipment 25 An Introduction to Electric Machinery almost all tools. Of course, generators are necessary to supply the power used by all these motors. Transformers 2 A transforn is a device that changes AC electric power at one voltage level to AC electric power at another voltage level through the action of a magnetic field. It consists of two or more coils of wrapped around a common ferromagnetic core. These coils are (usually) not directly connected The only connection between the coils is the common magnetic flux present within the core. 3 In a modem power system, electric power is generated at voltages of 12 to 25 kV. Transformers step up the voltage to between 110 kV and nearly 1000 kV for transmission over long distances at very low losses. Transformers then step down the voltage to the 12- to 34.5-kV range for local distribution and finally perm.it the power to be used safely in homes, offices, and factories at voltages as low as 120 V. AC machinery fundamentals 4 AC machines are generators that convert mechanical energy to AC electrical energy and motors that convert AC electrical energy to mechanical energy. The fundamental principles of AC machines are very simple, but unfortunately , they are somewhat obscured by the complicated construction of real machines. There are two major classes of AC machines - synchronous machines and induction mac es. Synchronous machines are motors and generators whose magnetic field current is supplied by a separate DC power source, while Unit 2 Electric Machinery and Electrical Equipment 25