外文翻译--电动机和数控技术.docVIP

Motors and Numerical Control Motors change electrical energy into mechanical energy . This is simply the mechanical forces between magnets .when two magnets (or electromagnets)approach each other ,one will be either pulled toward or pushed away from the other . 1.CONSTRUCTION Each type of motor is built to do its own special job .All of them have two main parts .One part is called the stator .The stator is stationary ;it does not move .The other part ,the rotor ,is mounted on bearings so it can rotate .The rotor shaft sticks out beyond the housing .For a motor ,the rotor shaft is coupled to a mechanical load . 2.MOTORS The power input to a motor is electrical .Voltage is applied to a motor’s terminals resulting in a current .The power output of a motor is mechanical .This power is transmitted by the rotor shaft as a torque .This torque tends to rotate a load , such as a fan or pump . As a motor drives a load , mechanical power is drawn from the motor .The motor ,in turn ,draws electrical power from the source at the same rate 3.NUMERICAL CONTROL The major disadvantage of machine tool automation thus far described lies in the economics of the process .It is expensive to tool a installations for automatic production .Therefore ,unless the part is to be made in very large numbers ,the cost becomes prohibitive .Great need exists for a method that permits rapid automatic production ,economical in job-lot amounts .The answer has been found in the numerical control of machine tools . Computer Numerical Control .Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers ,letters ,and other symbols .The numbers ,letters ,and symbols are coded in an appropriate format to define a program of instructions for a particular workpiece or job .When the job changes ,the program of the particular workpiece changes .The capability to change the program is what makes NC suitable for low-volume and