Расскажите, в чем состоит разница между током статора без нагрузки и пусковым током

2.11.7 Прочтите последний абзац текста и скажите, что происходит с двигателем постоянного тока, если «тяжелый» пусковой ток превышает номинальный

Расскажите все, что вы знаете о двигателе постоянного тока

Alternating Current Motors

Переведите и запомните следующие словосочетания

squirrel-cage motor, single-phase motor, three-phase motor, phasewound motor, wound-rotor motor; low speed motor, voltage drop, flexible lamination, considerable voltage drop, deenergization of metal parts, constant disinformation, decomposition of structure, lengthy period of (dis)use, low/high speed operation.

Прочтите и переведите текст; найдите все определения, выраженные простыми и составными существительными; скажите, каким образом с их помощью характеризуются электродвигатели переменного тока (alternating current (a.c.) motors)

1. A. c. motors are subdivided into single- and three-phase motors. The single-phase motors are used in refrigerators, washing machines, floor polishes, etc.

2. As to the three-phase motors they are widely used in industry. The two main designs of three-phase motors are highly in use nowadays: phase-wound motors and squirrel-cage motors.

3. The a. c. phase-wound motor, like the d. c. machines, includes the stationary part-the stator, and the rotary part-the rotor. The stator consists of a frame with a core. The rotor, like the d.c. armature, consists of steel laminations, insulated from one another; the three-phase winding is connected to the three rings insulated from one another by means of brushes. By these brushes the rotor is connected to the starting rheostat. As soon as the motor is started, the rotor current drops to its normal value and the starting rheostat stops operating.

4. The rotor of the squirrel-cage three-phase motor differs from that of the wound-rotor motor. Its rotor is a winding built in the form of a cylindrical cage. The cage consists of copper bars attached to the copper rings; this kind of rotor is termed squirrel-cage. Squirrel-cage motor rotors are supplied with ventilation. The ventilation serves to prevent their overheating.

5. Installed motors are given a test at no-load and under a load. No-load test serves to check the motor for noise. In the process of test no abnormal noise should be heard. In case this noise appears, the motor must be disconnected. After the check, the motor is given one more, no load test.