DOL and Auto Transformer Starting — Lesson 3

This lesson covers the concepts of reactor and auto transformer starting in three-phase induction motors. It explains how the starting current and torque are reduced by a factor of X and X square respectively in reactor starting, compared to direct on-line start. The lesson then moves on to discuss auto transformer starting, where the starting current is reduced by a factor of X square, providing some relief. The lesson also introduces the star-delta method of starting, which can only be applied if the motor is designed for delta connected stator winding. The lesson concludes by explaining how to implement star-delta starting in a laboratory setting.

Video Highlights

00:45 - Explanation of auto transformer starting
11:20 - Discussion on the star-delta method of starting
27:18 - Implementation of star-delta starting in a laboratory setting

Key Takeaways

- Reactor starting reduces the starting current by a factor of X and starting torque by a factor of X square.
- Auto transformer starting reduces the starting current by a factor of X square, providing some relief.
- The star-delta method of starting can only be applied if the motor is designed for delta connected stator winding.
- Star-delta starting can be easily implemented in a laboratory setting, provided all six terminals of the motor are available.