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

Electrical machines are the 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 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 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 lesser practical applications.

While AC motors have 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

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