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5 Different Types of Alternators

Different types of alternators laid on flat surface.

I still remember running through the rain to my car, getting soaked, but needing to get some supplies. I finally got in the car, turned the key to start, and heard “click-click-click.”

I thought it was the dreaded dead battery, but I discovered the battery was fine after some inspection, and the alternator was at fault.

If you are like me, you never consider how hard the alternator works and how you know when it doesn’t. The battery does not get charged when an alternator fails and eventually runs down to the clicking sound.

So, this article is to explain all the different types of alternators, how they work and why they are so important.

What is an alternator?

The technical description is an electrical device (also called a synchronous generator) that converts mechanical energy to electrical energy by adhering to a specific voltage and frequency while converting the electrical energy into an alternating current (AC).

Or, in plain speak, it takes energy from the power of a running engine to produce electrical power for the vehicle and recharge the battery. 

The alternator performs vital functions for the proper functioning of a vehicle and is easy to overlook until the unit fails. Then sitting in a parking lot with a dead battery will tell you it is too late to check how it works.

So always pay attention to any telltale signs discussed further in this article on how to be prepared.

What are the different types of alternators?

 There are five basic types of alternators, depending upon their design and application. The classification type is based upon the following types of applications:

  • Automotive Type – Most commonly found in today’s automobiles and vehicles. 
  • Diesel Electric Locomotive Type – Diesel-electric alternators are designed for multiple applications, including locomotives and city buses. 
  • Marine Type – Typically used for marine environments and applications.
  • Brushless Type – Used in electrical power generation plants as a primary power source.                                       
  • Radio Alternator Type – Primarily used for low-frequency radio transmissions. 

Now, let’s examine each alternator type more closely.

1. Automotive Type Alternators 

DB Electrical 400-14083 Alternator Compatible With/Replacement For Ford 4.6L 4.6 Crown Victoria Town Car Grand Marquis 06 07 08 2006 2007 2008 5W1T-10300-AB 5W1Z-10346-AA 6W1T-10300-AA 6W1Z-10346-AA

The automotive alternator generates electrical power by being bolted to the engine and driven by a serpentine belt or drive belt that rotates the alternator pulley. This type of alternator is used for almost all combustion engine vehicles and some specific hybrid vehicles.

We seldom think about the alternator until the “click-click-click” sound appears. Then, when the vehicle does not start, we pay attention. The alternator’s primary function is providing power to charge the battery.

Still, when the alternator fails, the battery may run the engine for a short time, but it too will eventually be depleted and fail. 

What to check for a bad automotive alternator?

The most typical indication of a failing electrical charging system is the iconic warning light shaped like a battery. There may also be an icon with the letters “CHARGE” appearing.

It may indicate either a failing battery or a bad alternator, especially if the lights do not go off after starting the engine. If the warning lights remain on, it indicates a problem with the vehicle’s charging system.

What to look for when the battery warning light comes on? Do the headlights become brighter when the engine is revved?

Fluctuating headlight brightness may indicate a bad alternator, weak battery, loose battery connections, or a serpentine belt that is worn or loose.

Do you hear a buzzing or whining sound from the alternator?

A failing alternator will often have a whining sound indicating worn bearings, or the alternator pulley could be defective.

2. Diesel Electric Locomotive Type

DB Electrical AND0214 Alternator Compatible With/Replacement For Kubota Tractor w / 2.8L Diesel Engine L2800 L3130 L3400 L3430 L39 L4300 M4700 M4800 M4900 M5400 M5700 MX5000F / 3A011-74010

Diesel-electric locomotive uses traction motors, or electric motors, to drive the locomotive. The power for these motors is derived from a complex electrical system, with the alternator being the heart of the electrical power.

Diesel engines power the alternator to generate AC electrical power for driving the traction motors. The electric traction motors provide propulsion power to the locomotive’s driving wheels, rolling the locomotive along the rail track. 

An auxiliary alternator generates power distributed throughout the train, including passenger cars, for powering lights, air conditioning, and other necessary passenger services.

The electric traction motors utilize alternators for power to drive the train due to the efficiency of AC alternators. Alternators produce AC power much more efficiently than generators that generate DC.

The locomotive type may use diodes and inverters to convert AC or DC power to the traction wheel motors. However, AC traction motors are estimated to have twice the adhesion to the track of a DC traction motor. In addition, an AC traction motor typically is half the weight of a DC motor while producing comparable power.

3. Marine Type Alternators


I can attest to the importance of having healthy marine alternators from firsthand knowledge. On a hot day in the middle of a lake, a dead battery when the marine alternator fails to keep it charged is not a fun deal.

Local calls for help when stranded on the water in a dead boat are not the same as sitting on the side of a road in a stalled vehicle calling the local garage. Make sure you are prepared and have enough ice on board the stalled boat for all the drinks!

Marine alternators are usually found in yachts and similar vessels with engine compartments and are comparable to automotive alternators. The marine alternator has design modifications specifically for working in salt-water and fresh-water environments.

Alternator durability is essential when large yachts may have two or more alternators to generate enough power for all the ship’s energy requirements.

An alternator must be certified explosion-proof for vessels with inboard engines for marine environments. For yachts and larger ship types, the alternator is explosion-proofed to ensure there is not any brush sparking in the engine compartment where explosive fumes may exist.

The alternator also has to have components, such as bearings, designed for harsh, corrosive salt-water environments.

4. Brushless Type Alternator

Powermaster 820512 Alternator

brushless alternator is typically a more efficient design than brushed alternators. Alternators that use carbon brushes with a single rotor to generate electricity are considered brushed alternators.

Alternators that have two spinning rotors to produce electricity without carbon brushes are known as, and you guessed it, brushless alternators. 

Brushless alternators create electricity with two rotors spinning and a small generator at the end. The electricity then is converted to an electric current for power.

With a more efficient design, a brushless alternator is typically used in applications requiring long-term use as a power generating system requiring high up-time.

Now, let’s take a look at comparing a brushless and brushed alternator.

Brushless alternator

Brushless alternator design is more efficient than brushed alternators. These are some Pros and Cons of the brushless alternator.


  • More durable and efficient with fewer parts 
  • Increased power output
  • Requires less maintenance expense
  • Uses less amperage for increased efficiency


  • More complex requiring microprocessor
  • More expensive than a brushed alternator
  • Increased complexity may affect power output reliability

 5. Radio Alternator Type

The Alexanderson Radio Transmitter was a breakthrough alternator technology in 1904 developed by Ernst F.W. Alexanderson, an engineer at General Electric.

The Alexanderson radio alternators provided the necessary power to transmit international radiotelegraph communications from 1904 to 1918.

The Alexanderson 200kw Radio Transmitter created many technological milestones, including:

  • It led to the creation in 1919 of the first American-controlled wireless communications company, Radio Corporation of America (RCA).
  • Created reliable communications with allies in WWI by utilizing the Marconi station in New Brunswick, NJ.
  • Became the sole communication device to communicate with Germany towards the end of WW1.
  • Dr. Ernst Alexanderson was awarded over 300 patents in his 75-year career.

The Alexanderson alternator technology was on the cutting edge in the 1900s and contributed significantly to the outcome of WW1. However, the last Alexanderson alternator discontinued operations in 1959 in Marion, MA.

However, reportedly functioning, there is still a working Alexanderson alternator in Grimetown, Sweden!


What are the differences between an alternator and a generator?

An alternator and a generator are both mechanical devices designed to generate electricity. You might consider an alternator a generator type, since they are both made to create electrical power.

Their primary differences are the methods used to generate electricity. Both devices take mechanical energy and convert it into electrical power.

Typically, alternators are internal devices found most often on vehicles and designed to run the engine, recharge the battery, and provide adequate power to run the vehicle’s electrical components.

A generator is usually an external device and is used as a primary electrical power source when it is engaged. For example, a generator can be life-saving when a storm knocks out a home’s power on an extremely cold or hot day.

Or, when a hospital’s power is lost, the generator can be large enough to provide adequate power to continue operations. 

Significant differences in electrical power generation

The significant differences between an alternator and a generator are:

  1.  Both devices can create alternating current (AC) but are different in converting it to direct current (DC).
  2. An alternator produces AC and converts it internally to DC, while a generator can create either AC or DC controlled by external regulators.
  3. The alternator’s magnetic field spins inside the stator (copper windings) while a generator’s stator is stationary, and the magnetic field revolves around it. 
  4.  Although an alternator is considered more efficient at generating electrical power, a generator has a higher capacity for larger applications.
  5. A generator can charge a dead car battery, but an alternator can not. 

What is the difference between AC and DC electrical power?

Sometimes it can be confusing what the differences are between AC and DC power supplies and electrical power output and how they may be applied differently.

For example, although an alternator creates AC power, within the alternator are complex circuits that convert AC to DC power output.

The primary difference in this discussion is that DC power is typically stored in batteries used in vehicles. In contrast, AC power is transmitted commonly by power distribution lines to homes and businesses.

How a battery stores DC electrical power?

A typical vehicle battery has both negative and positive terminals. Charged electrons flow through a conductor traveling from one terminal to the other.

The sealed lead-acid battery typically found in most vehicles stores DC from an alternator in a set of six cells creating 12 volts. The battery’s power and capacity vary depending upon the vehicle’s power requirements.

Newer vehicles, especially EV (Electric Vehicles) or Hybrid (combination of gas combustion and electrical motors), have lithium-ion batteries. The significant advantage of using lithium-ion batteries is the higher storage capacity and up to ten times the life of a lead-acid battery.

The advantage of DC batteries for vehicles is delivering a quick burst of high amperage energy to crank and start an engine. This burst of power is most welcome on those cold mornings when the engine and outside temperatures are frigid. 

Typically, lead-acid batteries are rated at amp-hours of cranking for a vehicle’s engine, each battery designed for specific requirements. For example, mid-size batteries may be adequate for large cars and SUVs with 50 amps-hours, but large trucks may require 75 amp-hour batteries.

Lithium-ion batteries are rated for maximum deliverable starting amps and not in cranking amp-hours. Therefore, lithium-ion batteries can be much lighter than lead-acid batteries since they are not restricted to adhering to amp-hours cranking. 

They do have one huge advantage: lithium-ion batteries have continuous power. A lithium-ion battery will deliver continuous amps for starting a motor, whether it is 90% charged or 5% charged.

A lead-acid battery will slowly discharge, and cranking amps drop until you hear the dreaded sound of an engine not getting enough power to start.