induction machines are motors and generators whose field current is supplied by magnetic induction(transformer action)into their field windings.The field circuits of most synchronous and induction machines are located on their rotors. In a synchronous generator,a DC current is applied to the rotor winding.which produces a rotor magnetic field.The rotor of the generator is then turned by a prime mover,producing a rotating magnetic field within the machine.This rotating magnetic field induces a three-phase set of voltages within the stator windings of the generator.The term synchronous refers to the fact that this machine's electrical frequency is locked in or synchronized with its mechanical rate of shaft rotation.The synchronous generator is used to produce the vast majority of electric power used throughout the world. Synchronous motors are synchronous machines used to convert electrical power to mechanical power.A synchronous motor is the same physical machine as a synchronous generator,except that the direction of real power flow is reversed. Since synchronous motors are usually connected to power systems containing generators much larger than the motors,the frequency and terminal voltage of a synchronous motor are fixed (i.e.the power system looks like an infinite bus to the motor). Induction motors In induction machines,the rotor voltage(which produces the rotor current and the rotor magnetic field)is induced in the rotor windings rather than being physically connected by wires.The distinguishing feature of an induction motor is that no DC field current is required to run the machine Although it is possible to use an induction machine as either a motor or a generator, it has many disadvantages as a generator and so is rarely used in that manner.For this reason,induction machines are usually referred to as induction motors. 26电气工程英语26 induction machines are motors and generators whose field current is supplied by magnetic induction (transformer action) into their:field ndings The field cuits of most synchronous and induction machin.es are located on their rotors. s In a synchronous generator , a DC current is applied to the rotor winding , which produces a rotor magnetic field. The rotor of the generator is then turned by a prime mover, producing a rotating magnetic field within the machine. This rotating magnetic field induces a three-phase set of voltages the stator windings of the generator. The term synchronous refers to the fact that this machine's electrical frequency is locked in or synchronized with its mechanical rate of shaft rotation. The synchronous generator is used to produce the vast majority of electric power used throughout the world 6 Synchronous motors are synchronous machines used to convert electrical power to mechanical power. A synchronous motor is the same physical machine as a synchronous generator, except that the direction of real power flow is reversed. Since synclrronous motors are usually connected to power systems containing generators much larger than the motors, the frequency and terminal voltage of a synchronous motor are fixed (i.e. the power system looks like an infinite bus to the motor). Induction motors 1 In induction machines, the rotor voltage (which produces the rotor current and the rotor magnetic field) is induced in the rotor windings rather than being physically connected by es. The stinguis feature of ai1 induction motor is that no DC field rent is required to run the machine. s Although it is possible to use an induction machine as either a motor or a generator, it has many disadvantages as a generator and so is rarely used in that manner. For this reason, induction machines are usually referred to as induction motors. 气工程英语