General Information for All Motors（所有汽车的一般信息）.pdfVIP

ELECTRIC MOTORS General Information for All Motors Electric motors, whether designed to operate on ac, dc, or both types of current, come in numerous shapes and sizes. All electric motors have one goal in common: to convert electrical energy into mechanical motion. Whether the application uses a general-purpose standardized electric motor or a motor intended for a specific task, the selection process must satisfy the dynamic requirement of the machine on which it’s applied without exceeding the motor’s rated temperature. The relationship between motor load and temperature is easy to remember: hp=550 ft-lb/sec W=N-m/sec the higher the load, the higher the tem- perature at which the motor operates. A Thus, the first and most important step motor’s maximum operating temperature in electric motor selection is determining determines its maximum load, typically load characteristics -- torque and speed specified as the amount of power the mo- versus time. Additional factors in motor tor can deliver on a continuous basis. selection are the mission goals, power Motor power is usually expressed in available, and cost. terms of horsepower (hp) or wattage (W). The first step in sizing an One horsepower represents approximately electric motor begins 746 Watts. So a 7.5-kW electric motor with determining does the same amount of work as a 10-hp the starting electric motor. and Of course, the real goal identifies how much work the motor can perform over time. Assuming there are no other losses in the system, a 1-hp motor can lift a 550-lb weight one foot in one second, or 550 ft-lb/sec. However, mechanical losses