Electric motor | Basic concepts

Chemical companies have mostly rotary equipments have motor. In this blog we will learn about motors in easy terms.

Basic concepts

Motors convert electrical energy in mechanical rotation.
Motor is creating magnetic field between rotor & stator wire winding which result in rotation
Basic components of motor
1. Stator - Body side winding
2. Rotor - Stem side winding
3. Bearing
4. Frame [ enclosure - In which motor is fitted ]
Motor types -
1. Induction motor
2. Direct current
3. synchronous motor

Component - Electric motor | Basic concepts

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Motor types

1. Induction motor

Winding in motor of rotor and stator is in opposite direction. current is in opposite direction magnetic field is generated and this is make motor rotate.

Commonly used motor in chemical industry in pumps, blowers, fans, conveyers.

2. Direct current motors

This motor is using unidirectional current. This motor is used in high torque starting and smooth operation on high operation.

3. Synchronous motor

There are two types of current AC & DC [ AC - Alternate current; DC - Direct current current ].

In this type of motor both type current is used. AC power is used by Stator & DC Power is used by Rotor.

DC power is single direction power which produces constant magnetic field. This gives constant thrust to rotor.

AC power is producing heat due to its magnetic amplitude is changing . This heat can be removed by fins on motor. AC power is also have much energy losses.

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Motor Characteristics

Motor speed

Motor speed or RPM is depends on 1. Frequency, 2. Number of poles on rotor.

Frequency = 50 Hz
Poles = 2, 4, 6, 8, 10, 12, 16 etc

Actual speed is less than theoretical speed is called Slip(%)

Motor Efficiency

Motor efficiency is defined as ratio of Mechanical energy delivered to Electrical energy input.

Motor efficiency is also depend n motor temperature. Totally closed and fan cooled motors are high efficient motors.

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Losses in motors are

1. Fixed losses - Magnetic core loss, Friction loss ( 8 - 12 % of total losses)
2. Variable losses - Resistance losses between Rotor & Stator(I²R), Stray load losses

, Other miscellaneous loss.

Efficiency improvement scopes
Stator (I²R)	Use more copper Large conductor Increase cross section area windings
Rotor (I²R)	Use large conductor bars Increase size of cross section
Friction and windage losses	Use of low loss fan design to reduce air movement loss
Stray load loss	Optimized deigned motor use Strict quality control while production in motor