DOL and Reactor Starting — Lesson 2

This lesson covers the different methods of starting a three-phase induction motor, focusing on the Direct Online (DOL) starting, reactor starting, and auto-transformer starting. It explains the concept of rated voltage and the problems that can arise when an induction motor is directly connected to the supply. The lesson also discusses the rotor resistance starter for slippering induction motors and the impact of starting current on the health of the motor and other connected devices. It further elaborates on the concept of reduced voltage starting and the use of reactors in the circuit to control the starting current. The lesson concludes with a comparison of the starting methods in terms of starting current and torque.

Video Highlights

00:43 - Explanation of Direct Online (DOL) starting
03:14 - Impact of starting current on the motor and other devices
07:25 - Comparison of starting methods
19:31 - Explanation of reactor starting
22:45 - Calculation of starting current and torque

Key Takeaways

- Direct Online (DOL) starting involves directly connecting the motor to the supply, which can lead to high starting currents.
- Rotor resistance starter for slippering induction motors involves connecting external resistances in the rotor circuit to control the starting current.
- The starting current can be detrimental to the motor and other connected devices due to the sudden voltage dip.
- Reduced voltage starting involves applying a reduced voltage at the motor terminals initially and then gradually increasing it.
- Reactor starting involves connecting reactors in the circuit to control the starting current.
- The starting current and torque can be calculated for different starting methods, providing a basis for comparison.