ELECTRIC MOTORS

By Manish Ravji Checked by Fatima

CONTENTS 1. Introduction to electric motors 2.Compound motors (DC)3.synchronous motor (AC)4.Stepper motor (Other Motors)5.How/Why are they used in industries?

INTRODUCTION TO ELECTRIC MOTORS In motors, they convert electric energy into mechanical energy. Electric motors play a main role in our daily life. The movement of any device is produced by an electric motor. Examples are Hair dryer, Disk drive and any more and this is all due to electric motors.

Electric motors can be divided into two basic groups, Direct Current (DC) motors, and Alternating Current (AC) motors. Although there are many designs of electric motors, the fundamental is the same. The technology behind electric motors is the ability to convert electrical energy to mechanical energy. The basic configuration is illustrated on the right.

When an electric current flows through a wire loop that is in a magnetic field, the loop will rotate and the rotating motion get transmitted to a shaft, providing useful mechanical work. In other words, an electric motor is all about magnets and magnetism. Basically, a motor uses magnets to create motion.

In the above diagram, you can see two magnets in the motor: The armature (or rotor) is an electromagnet, while the field magnet is a permanent magnet.

DC MOTORS

Compound motor:

A compound motor is essentially a combination of series DC motors and shunt DC motor. the stator is connected to the rotor through a compound of shunt and series windings, if the shunt and series windings add up together, the motor is called comulatively compounded. If they subtract from each other, then a differentially compounded motor results, which is unsuitable for any application.

Speed controlThe DC compound motor can be controlled very easily. It all depends on how much voltage is being inputted into the motor.

• AC motors have constant speeds but DC motors have different speeds.

• However, this was the situation before three decades. But, the advent of solid-state components and microprocessor-based controls has revolutionized the way we control motor speeds.

• Today, a solid-state AC variable-frequency motor drive can be used to vary the speed of an AC motor as easily as that of DC motors.

AC MOTORSynchronous Motor: So called because rotor tries to line up with the rotating magnetic field in the stator. It has the stator of an induction motor, and the rotor of a dc motor. Main Features of Synchronous Motors

• Synchronous motors are inherently not self starting. They require some external means to bring their speed close to synchronous speed to before they are synchronized.

• The speed of an AC motor is the speed of the stator’s magnetic field rotation. This is the motor's theoretical speed since the rotor will always turn at a slightly slower rate.

• This motor has the unique characteristics of operating under any electrical power factor. This makes it being used in electrical power factor improvement.

OTHER MOTORS

Stepper Motor: a special type of synchronous motors. Rotates a number of degrees with each electric pulse.

What are stepper motors good for?

• Positioning – Since steppers move in precise repeatable steps, they excel in applications requiring precise positioning such as 3D printers, CNC, Camera platforms and X,Y Plotters. Some disk drives also use stepper motors to position the read/write head.

• Speed Control – Precise increments of movement also allow for excellent control of rotational speed for process automation and robotics.

• Low Speed Torque - Normal DC motors don't have very much torque at low speeds. A Stepper motor has maximum torque at low speeds, so they are a good choice for applications requiring low speed with high precision.

HOW/WHY ARE THEY USED IN THE INDUSTRIES?

DCCumulative compound wound motors are virtually suitable for almost all applications like business machines, machine tools and mixers etc. Compound motors are used to drive loads such as shears, presses and reciprocating machines.

ACAC Motors are primarily used in domestic applications due to their relatively low manufacturing costs, and durability, but are also widely used in industrial applications. AC Motors can be found in numerous home appliances and applications, including: Clocks, Power tools, Disk drives, Washing Machines and other Home Appliances. An AC Controller can be used in many different industrial and commercial applications. Most often used to control fans in air conditioning and heating systems, the AC Controller allows for more control of the airflow. The AC Controller also aids in adjusting the speed of pumps and blowers. More recent applications include conveyors, cranes and hoists, machine tools, extruders, film lines, and textile-fiber spinning machines.Other

Stepper motor can be used to make robots. These robots are used in manufacturing when making products. They are very precise and accurate however they may have some faulty and they are very expensive to repair. They use a stepper motor because of the speed, low speed torque and the positioning.