Dynamo vs Alternator: Difference and Comparison

Electricity forms the most indispensable part of our life today. It provides us with lighting, entertainment, and a lot of things. It is impossible to imagine life without electricity.

Earlier, humans used batteries for electricity. But it was slowly found that batteries were not cost-effective or reliable. 

Modern homes are mostly powered by electricity. It is very convenient and can be produced using anything from coal, oil, wind, and waves. 

We need a steady supply of electrical energy if we want to run anything, either a television, a toaster, or an MP3 player.

The basic law of physics, “Conservation of Energy”, explains how energy can be obtained and how we cannot get energy.

There is a fixed amount of energy in our universe; all we can do with this energy is convert it into any useful form. Thus, we require certain appliances to convert energy and get a regular supply of electricity.

 These appliances can be a generator, a motor, a dynamo, an alternator, etc. Here we will see how a dynamo and an alternator will function and differ.

Key Takeaways

  1. A dynamo generates direct (DC) electricity, while an alternator produces alternating (AC) electricity.
  2. Dynamos have a commutator and brushes to convert the AC voltage generated to DC voltage, while alternators use diodes to convert AC to DC.
  3. Dynamos are less efficient and heavier than alternators, while alternators are more efficient and lighter than dynamos.

Dynamo vs Alternator

A dynamo generates direct current (DC), where a rotating armature is placed between two permanent magnets, and the voltage output is low and constant. An alternator uses a rotating magnetic field and a stationary armature to generate an AC, having a higher and variable voltage output.

Dynamo vs Alternator

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Comparison Table

Parameters of ComparisonDynamoAlternator
DefinitionDynamo is a machine that produces direct current flowing in the same direction.An alternator is a machine that produces alternating current flowing in different directions.
Magnetic fieldStationaryRotating
Input supplyTakes input supply from the rotorTakes input supply from the stator
Energy efficiencyIt is less energy efficientIt is highly energy efficient
Range of Rotations Per Minute (RPM)Supports less range of RPMSupports a wide range of RPM
Brush durabilityIt has less brush durabilityIt has high brush durability
Charging dead batteryIt can be used to charge a dead batteryIt cannot be used to charge a dead battery
MaintenanceIt has high maintenance chargesIt has low maintenance charges

What is Dynamo?

Dynamo is an electrical device that produces direct current flowing in one direction. It is used for generating electrical energy. It converts mechanical energy into electrical energy.

The dynamo was first designed by Nikola Tesla. But the credit for conceptualizing the dynamo is given to Michael Faraday.

Faraday first proposed that a moving magnet in a closed electric circuit can induce electric current to flow.

The dynamo works on the concept of electromagnetic induction. When the coil is linked with the magnetic field changes, an induced emf is set up.

The dynamo consists of several parts like a yoke, poles, armature, stator, rotor, brushes, etc. The essential parts of the dynamo are the stator and rotor.

The coils in the dynamo rotate through the magnetic field. Split ring commutators are used to connect to an external circuit.

This split ring commutator switches the connections at every half-turn, thus keeping the current flowing in the same direction.

The brush ensures a continuous electrical connection without inhibiting the commutator’s movement.

There are two sets of brushes – one which taps the power to go to the main circuit and another set of brushes that take power from the armature to get the stator’s magnets powered. 

The armature holds onto a small amount of magnetism in its iron core.  When it begins to turn, a little bit of power is generated, which excites the solenoids in the stator.

Slowly, the voltage rises, and the dynamo gets to full power.

If a battery has to be prevented from getting overcharged, then the dynamo’s output should be regulated. This is done by the regulator that changes the current as needed.

A Dynamo is quite expensive and big when compared to an alternator.  Dynamos produce electrical power in automobiles, ships, trains, aircraft, etc.


What is an Alternator?

An alternator is a machine that produces an alternating current that constantly changes its direction. It converts mechanical energy into electrical energy. Alternators were created by Hippolyta Pixi, a French inventor, in 1832.

There are different types of alternators depending on their applications and design.

The alternator consists of two main components – Rotor and Stator. The rotating part is the rotor, whereas the stator is the stationary part. 

The alternators work on the principle of electromagnetic induction, according to which a conductor, magnetic field, and mechanical energy are needed to produce electricity.

When the speed of the alternator is reduced or decreases, then the current output also reduces or decreases. 

Also, the current output reduces or decreases when the temperature of the alternator increases. When the alternator runs at a low speed, the efficiency of the alternator automatically reduces. 

The brushes in the alternator provide power to the coil mounted on the rotating shaft. These brushes provide the direct current through two slip rings.

 The alternator’s brushes are quite durable and last longer when compared to that of the dynamo, as the brushes only require enough electricity to get the rotor powered.

The alternator is used in the following applications:

  1. Automobiles
  2. Marine applications
  3. Radiofrequency transmission
  4. Diesel electrical multiple units
  5. Electrical power generator plants

The alternator is a cheap device which is light in weight. The construction of the alternator is simple and low in maintenance. The alternator is robust and more compact.

 But the alternator has advantages as well. It needs transformers to run and gets overheated when the current is high.


Main Differences Between Dynamo and Alternator

  1. The basic difference between Dynamo and Alternator is that Dynamo produces a direct current, which flows in one direction. In contrast, an Alternator produces an alternating current which changes its direction constantly.
  2. The magnetic field of the Dynamic is stationary, whereas the magnetic field of the Alternator is rotating.
  3. The input supply taken by the Dynamo is through the rotor, whereas the Alternator takes its input supply through the stator.
  4. The Dynamo has less energy efficiency when compared to the Alternator, which has very high energy efficiency.
  5. The range of Rotations per Minute(RPM) of a Dynamo is less, approximately <2000RPM, whereas the RPM of an Alternator will range from 6000RPM to 12,000RPM
  6. Dynamos have high maintenance costs whereas Alternator requires very little maintenance.
  7. The brushes of the Dynamo do not last long as split rings are used and get worn off quickly, whereas the Alternator brushes last long as solid rings are used and do not get worn off easily.
  8. A Dynamo can be used to charge a dead battery, whereas an Alternator cannot be used to charge a dead battery.
Difference Between Dynamo and Alternator
  1. https://link.springer.com/content/pdf/10.1007/978-1-349-06180-8_6.pdf
  2. https://link.springer.com/chapter/10.1007/978-1-349-03176-4_5

Last Updated : 11 June, 2023

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4 thoughts on “Dynamo vs Alternator: Difference and Comparison”

  1. The information provided is valuable. It’s interesting to know about the differences between a dynamo and an alternator.

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