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

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”.

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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 machine which 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 machine which 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-Invarying (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

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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:

• Ceiling fans
• AC Table fans
• Drill machines
• Washing machines

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4} Synchronous electrical machine (generator and motor)

Flux: Time-Invarying (rotating).

Conductor: stationary

Hence, dynamically induced EMF.

Applications:

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