Continuous Electro-mechanical energy conversion devices are known as Electrical machines. Which is a reversible process.

## Table of Contents

Electrical machines are machines that are either used to transfer or the generation of Electrical power. These may be low-power or high-power devices(in mV or kV). Here I am discussing the high-power devices in this article.

## Types of Electrical Machines:

- Transformer (not an electrical machine, it is a static device).
- DC Machine (generator and motor).
- Induction Machine (generator and motor).
- Synchronous machine (generator and motor).

Basic things to know before jumping into electrical machines for better understanding!!!

Much useful if you are an engineering student

**Things to know:**

#### From Electrical NETWORKS

- Ohm’s law.
- KVL and KCL (‘kirchhoff’s voltage law’ and kirchhoff’s current law).
- Basic network analogy (mesh Theorem, nodal theorem, Thevenin’s Theorem, MPPT, Millman’s theorem).
- Ideal voltage and current.
- what is an open/ short circuit?
- what is source or sink?
- star-delta Equivalence.
- sinusoidal and steady-state Response in AC (Alternating Current).
- RLC circuit.
- Phasor diagrams. (very important).
- Instantaneous power, Active power, reactive power, and complex power.
- Balanced 3-Phase AC system {DELTA and STAR connection}.

#### From **Magnetism**

- Ampere Circuital Law.
- Series, parallel magnetic circuits.
- Faraday’s 1st and 2nd law.
- Lenz’s law (mainly for the direction of the current I).
- Flemming’s “Left-hand rule” and “Right-hand rule”.

## 1} Transformer

The transformer is not an electrical machine, it is a static device, it only changes the voltage level from one level to another level. In this Energy conversion/ transfer is due to the mutual flux.

Flux: Time-varying (stationary).

Conductor: Stationary.

Hence, here is only **statically induced EMF** (Electro-Motive Force). Because it has primary winding and secondary windings physically connected by the core). Which is non-movable.

## 2} DC electrical machine (generator and motor)

DC machine is the common name given for the DC Generator and DC motor.

It works on the principle of Faraday’s Law of EMI (Electro-Magnetic Induction).

**DC Generator :**

Rotating

electrical machinewhich is designed to take the advantage of Electro-magnetic induction in order to convert mechanical energy into DC electrical energy.

- converting “mechanical Energy” to “Electrical Energy”.
- Voltage is produced {Simultaneously torque is also produced in order to oppose the applied torque}.

**DC motor :**

Rotating

electrical machinewhich is designed to take the advantage of Electro-magnetic induction in order to convert DC electrical energy into mechanical energy.

- Converting “Electrical Energy” to “mechanical Energy”.
- Mechanical torque is produced {Simultaneously opposite EMF (back EMF) is also produced to oppose the applied EMF.

Hence DC machine can be used as a Generator as well as a Motor.

Flux: Time-**In**varying (stationary).

Conductor: Rotating

Hence, **Dynamically induced EMF**

DC Generator = AC Generator + commutator (Split Rings)

*Applications* :

- DC Generator is not used in vast applications (because for heavy power usage its size increases)
- DC Motors are widely used in electronics with low power.
- Toys
- trimmers
- mobile vibrations
- drones etc

## 3} Induction electrical machine (generator and motor)

Due to complex construction, commutation problems, and maintenance. DC machines find fewer practical applications.

While AC motors have a simpler construction and less maintenance. Hence, these are the most popular (85% motors).

These work on the principle of **RMF (Rotating Magnetic Field).**

Flux: Time-varying (stationary).

Conductor: Stationary.

It is nothing but a rotating transformer. Because its windings are not physically connected by the core.

*Applications*:

*Applications*

- Ceiling fans
- AC Table fans
- Drill machines
- Washing machines

## 4} Synchronous electrical machine (generator and motor)

Flux: Time-**In**varying (rotating).

Conductor: stationary

Hence, dynamically induced EMF.

*Applications*:

- Hydropower plants
- Wind power plants
- Also for maintaining reactive power in the power system