1 / 17

AC Machines

AC Machines. 6077SA NUE 046. 3 Phase Induction Motor Characteristics. Interpret information from torque/slip curves of AC induction motors List the operating characteristics of squirrel cage induction motors List the operating characteristics of slip ring induction motors

ronli
Download Presentation

AC Machines

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AC Machines 6077SA NUE 046

  2. 3 Phase Induction MotorCharacteristics • Interpret information from torque/slip curves of AC induction motors • List the operating characteristics of squirrel cage induction motors • List the operating characteristics of slip ring induction motors • Identify details from motor nameplates • Calculate the efficiency of induction motors At the end of this section you will be able to:

  3. Revision • What determines the synchronous speed? • Why can’t the rotor operate at synchronous speed? • What do we call the difference between nR and n? • How do we work out the percentage slip of a motor?

  4. Motor Starting • Greatest relative speed between RMF & Rotor conductors • Induced voltage greatest • Equivalent to a transformer with a shorted secondary • Frequency is highest • Rotor torque must be higher than the apposing torque for the rotor to accelerate.

  5. Motor Running • As load torque increases • Rotor RPM drops • Relative speed between RMF & Rotor conductors increases • Rotor current increases • Rotor torque increases • Rotor RPM stabilises

  6. Rotor Current • Torque caused by induced current in rotor conductors • Rotor current is a result of:- • Rotor speed • Rotor impedance Frequency Resistance Inductive reactance

  7. Rotor Current • High frequency in rotor conductors • More metal surrounding conductor the deeper in the rotor. • L is highest in that part of the conductor • XL is highest • I is lowest • Effective CSA is reduced • Current is limited

  8. Torque Speed Curve Synchronous speed Torque Rated torque Rotor Speed Rated speed

  9. Torque Slip Curve Synchronous speed Rated speed Torque Rated torque 0 Slip % 100

More Related