AC motors can be divided into 1. and synchronous motors. In the first case, the rotor turns at a 2. speed than the rotating magnetic 3. . They include 4. -phase motors, suitable for small 5. , and 6. -phase motors, widely used for 7. machinery. In synchronous motors the rotor turns at the 8. speed as the magnetic 9. ; they are used in applications requiring 10. and precise speed.
DC MOTOR TYPES
DC motors include 11. and brushless types. In the first type, brushes connect the 12. to the rotor; they are used for industrial heavy machinery. Brushless motors use 13. circuit control and are suitable for applications requiring more 14. control. A common brushless example is the 15. motor, used in 3D 16. , CNC, and welding machines.
8. Read the sentences and decide which type of motor they refer to.
1. The rotor turns at the same speed as the magnetic field: 2. Carbon brushes connect the commutator to the rotor: 3. It is powered by single-phase alternating current: 4. It divides a full rotation into smaller steps: 5. It is powered by electromagnetic induction: 6. It is usually employed in 3D printers: 7. Brushes are substituted by electronic controls: 8. It is also known as an “asynchronous motor”: 9. It is self-started: 10. It is one of the most widely used brushless motors:
9. Listen to an expert talking about the main types of AC motors and fill in the table.
Synchronous motors vs. Induction motors
Magnetic field current Synchronous motors: supplied by a separate supply current Induction motors: supplied by electromagnetic 1.
Rotational speed Synchronous motors: 2. as the mains power supply frequency Induction motors: 3. from the magnetic field