机电一体化专业外文翻译--感应电机.doc

外文译文:
Induction Motor
1 Starting an induction motor
High-inertia loads put strain induction motors because they prolong the starting period. The starting current in both the stator and rotor is high during this interval so that overheating es a major problem. For motors of several thousand horsepower, a prolonged starting period may even overload the transmission line feeding the plant where the motor is installed. The line voltage may fall below normal for many seconds, thus affecting other connected loads. To relieve the problem, induction motors are often started on reduced voltage. This limits the power drawn by the motor, and consequently reduces the brie voltage drop as well as the heating rate of the windings. Reduced voltage lengthens the start-up time, but this s usually not important. However, whether the start-up time is long or short, it is worth remembering the following rule for a motor that is not loaded mechanical:
Rule I - The heat dissipated in the rotor during the starting period (from zero speed to final rated speed) is equal to the final ic energy stored in all the revolving parts.
This rule holds true, irrespective of the stator voltage or the torque-speed curve of the motor. Thus, if a motor brings a massive flywheel up to speed, and if the energy stored in the flywheel is then 5000 joules. the rotor will have dissipated 5000 joules in the form of heat. Depending upon the size of the rotor and its cooling system, this energy could easily produce overheating.
2 Plugging an induction motor
In some industrial applications, the induction motor and its load have to be brought to a quick stop. This can be done by interchanging two stator leads, so that the revolving field suddenly turns in the opposite direction to the rotor. During this plugging period, the motor acts as a brake.
It absorbs ic energy from the still-revolving load, causing its speed to hill. The associated mechanical power P, is entirely dissipated as heat in the rotor. Unfo