Induction Motor Construction (Squirrel Cage Rotor)

Summary

This video explores the induction motor, a widely used and reliable electric motor favored for its simplicity and ruggedness. It covers the history of its invention, highlighting both Nikola Tesla and Galileo Ferraris' contributions. The video provides a detailed explanation of the motor's construction, including its key components such as the terminal box, fan, rotor, stator, and squirrel cage rotor. It also highlights the advantages of induction motors, including their robustness, efficiency, and lower maintenance requirements, making them ideal for industrial use.

Takeaways

• 😀 Induction motors are the most common type of electric motor in the world, making up 90% of industrial motors.
• 😀 Induction motors are known for their ruggedness, simplicity, reliability, and economy.
• 😀 The invention of the induction motor is attributed to both Nikola Tesla and Galileo Ferraris, who made independent discoveries.
• 😀 Nikola Tesla's induction motor was patented in the U.S. in 1888 and played a key role in its commercial success.
• 😀 The terminal box of an induction motor is used for cable connection and consists of screws, a lid, a gasket, and a cable gland.
• 😀 The fan on the motor helps cool it by drawing air through the motor casing and over heat ventilating fins.
• 😀 The flange is a steel ring used to connect sections of pipes or join equipment like pumps and valves.
• 😀 The motor housing, or end bracket, supports the bearing and protects electrical and rotating parts inside the motor.
• 😀 The stator of the motor is built with high-grade steel laminations, which carry the alternating magnetic field that creates motor operation.
• 😀 The rotor, made from laminated cores, contains conductive bars (copper or aluminum) and forms a squirrel cage structure, which helps the motor operate efficiently and reduce maintenance.

Q & A

What makes induction motors the most common type of electric motor in the world?

Induction motors are favored for their ruggedness, simplicity, reliability, and economy. These qualities make them ideal for industrial use, with 90% of industrial motors being induction motors.

Who are considered the inventors of the induction motor?

The induction motor was independently invented by both Nikola Tesla and Galileo Ferraris. Tesla filed a patent for it in 1888, but many believe the invention must be shared with Ferraris.

Why is Nikola Tesla often credited with the invention of the induction motor?

Nikola Tesla is often credited with the invention because of his patent (U.S. Patent 381968, granted in 1888) for the induction motor, which led to a commercial success of the technology.

What are the main components of an induction motor's terminal box?

The terminal box consists of screws, a terminal box lid, a gasket, the terminal box case, and a cable gland, which allows the power cable to be fixed and provides power to the motor.

How does the fan in an induction motor contribute to its operation?

The fan pulls air into the motor and circulates it around the outside of the case, passing it over heat ventilating fins. This cooling process helps to prevent the motor from overheating.

What is the function of the flange in an induction motor?

The flange is a steel ring designed to mechanically connect sections of the motor, such as the pipe, valve, or pump, and secure them to the motor's housing.

What is the role of the shield in an induction motor's housing?

The shield, also called the end bracket or end bell, supports the bearing and acts as a protective guard for the electrical and rotating components inside the motor.

How is the stator of an induction motor constructed?

The stator consists of a high-grade alloy steel core made up of laminated stampings. These laminations are insulated from one another with a thin varnish layer, and they house the stator windings which are powered by a three-phase supply system.

What is the significance of the rotor's laminated cylindrical core in an induction motor?

The rotor’s laminated cylindrical core, made of the same material as the stator, helps to reduce eddy current losses. The core is slotted on the outside to receive conductors, which are connected by short-circuiting rings at the rotor’s ends.

What advantages does the squirrel cage rotor have over other types of rotors?

The squirrel cage rotor is cheaper, more robust, and requires less maintenance because it does not use brushes. It also has a higher power factor and efficiency, leading to smoother and quieter motor operation.