Explain with reason why is not advisable to start an induction motor above 25kw direct on line starter?

It is not advisable to start an induction motor above 25kW with a direct on line starter because starting a motor of this size directly on line can cause a high inrush current, which can lead to voltage dips in the electrical system and potentially damage the motor windings.

Starting a motor of this size directly on line can also cause mechanical stress on the motor and connected equipment, leading to premature wear and potential breakdowns. Additionally, starting a motor of this size directly on line can result in a sudden and abrupt start, which can be dangerous for both the motor and the connected machinery.

To avoid these issues, it is recommended to use a soft starter or a variable frequency drive (VFD) to gradually ramp up the motor's speed and reduce the inrush current during startup. This will help protect the motor and connected equipment, as well as ensure a smoother and more controlled start-up process.