What is the Core Function of a Self Exciting Alternator?

Self exciting alternators are becoming popular in the automotive industry. Their safety and efficiency make them a fantastic choice for extreme conditions. Using a self exciting alternator is a great way to maximize your battery’s capacity.

Unlike conventional alternators, this type of alternator is less likely to fail. Their minimal moving parts make them more reliable. They are also immune to damages caused by voltage surges. This is an excellent alternator if you desire efficiency and cost-effectiveness.

Let’s go into more detail about what a self exciting alternator is. We’ll also examine why an exciter is used in an alternator, and how to excite an alternator.

alternator self exciting

What is a Self-exciting Alternator?

A self exciting alternator is an alternator that builds a magnetic field by itself. It does this without an external electrical field. This alternator uses self-generated electricity. It delivers higher currents than conventional brush-type alternators.

The term “self-exciting” refers to the alternator’s ability to wake up and start charging. This occurs without a switched 12-volt wire. This type of alternator is also known as a single wire alternator, as it sparks up itself. This application reduces the need for external wiring and connections.

Two significant factors distinguish a self exciting alternator from other conventional alternators. Firstly, the alternator creates a field with a permanent magnet. This triggers the rotor’s rotation.

Secondly, the stator is designed with several coils connected in series. As a result, the coils experience a constant current flow, which powers the motor.

Furthermore, the self-exciting alternator uses an internal regulator. This helps to sense the battery’s voltage. Then, it sends an exciter current to the alternator’s rotor to start the generator in the alternator. The alternator’s voltage is then regulated to the car’s needs.

The self-exciting alternator ensures that your car operates safely and efficiently. It allows electrical power to be available, even when the engine isn’t running. Using this type of alternator is a great way to save a lot of energy.

Besides the capacity for high efficiency, 1-wire alternators are also resistant to blown fuse. This is a major advantage it has over regular alternators. Most conventional alternators are subject to voltage surge issues.

Why Exciter is used in Alternator

An alternator uses an exciter to check the generator’s output and regulate the magnetic field. This operation helps to maintain the needed voltage.

An increase in the generator’s load triggers an increase in current flow. This results in a voltage decline.

The exciter creates the electrical power required for the alternator to generate electricity. This component is a small rotating magnet spun by the main drive belt. As a result, it produces a field in the main winding of the stator of the alternator.

This field induces a current in the rotor winding, causing the rotor to rotate inside the stator. This in turn produces a voltage output.

Without an exciter, the alternator cannot produce the required voltage. Therefore, the battery may not be able to charge. Other electrical components will not also be adequately powered.

Additionally, the exciter helps to ensure proper control of the field current. This allows for a more consistent output voltage when the alternator is running.

Furthermore, the exciter enables a smooth start-up by limiting the initial field current. It also ensures that the alternator is not overloaded at start-up. Typically, the exciter plays a vital role in an alternator’s performance.

How to Excite an Alternator

Understanding how to excite an alternator is pretty straightforward. You’re good to go once you have the required tools for the job. Some of the tools needed to excite a 1 wire alternator include the following:

  • A DC motor
  • An alternator
  • Multi-meter
  • Drive belt
  • Mobile charger
  • Vice
  • Crocodile clips 12V bike headlamp bulb
  • Two laptop chargers
  • Wooden board 30X30 cm

You are good to go once you have the equipment listed above. Now follow the procedure below to excite your car’s alternator.

Step 1: Begin with the mechanical connections

Firstly, connect a pulley to a 500W DC motor shaft. Then, take a wooden board and carefully mount the motor on one side.

Get a big vice and strategically position it on the flip side of the board. After that, use screws to mount the vice on the board. Then, mount the alternator on it. Thereafter, use a pulley to connect the DC motor and the alternator.

Step 2: Perform the electrical connections.

Now, carefully connect the positive red wire brushes. Connect them to the alternator’s main positive terminal.

Then, connect the negative black or blue terminal of the brush from the rotor field. Connect them to any part of the alternator since it’s at a ground negative.

Step 3: Connect the mobile charger to the alternator

Get a 5-volt mobile charger. Then, connect its positive cable to the alternator’s major positive terminal. After that, attach its negative wire to any part of the alternator.

Step 4: Rotate the alternator’s shaft

Finally, use any mechanical rotating source, the DC motor, to rotate the alternator’s shaft. When the system gets in motion, disconnect the mobile charger. Once that is done, the alternator will automatically be excited.

Alternatively, you could follow the below video

How to Excite an alternator YouTube

Meanwhile, perform this operation carefully to avoid unnecessary complications. If you’re not sure of doing an excellent job, kindly contact an expert auto technician to handle it.

Nevertheless, exciting an alternator may be easy. This is true if you’ve been handling other DIY operations. Ensure to follow the instructions above carefully. With that, everything will come out excellently well.

What happens if Alternator is Over Excited?

An overexcited alternator will supply too much current through the electrical system. This can cause components to fail.

In most modern cars, the alternator is responsible for charging the battery. It also supplies power to the other electrical components. These components include the headlights, air conditioner, radio, etc.

Therefore, the components can have severe impacts if the alternator is overexcited. The alternator will produce more current than the electrical systems can handle.

Furthermore, overexciting the alternator can cause heat buildup. This can lead to alternator failure. There can as well be fire outbreak. This occurs when the component experiences extreme temperatures due to the excess current.

An overexcited alternator can utterly damage the components it powers. Too much voltage can create high-amperage surges. This occurrence can cause excessive wear and tear on electrical components. The wiring may not also be spared.

Too much voltage can even cause the components to melt or be destroyed. When this happens, the vehicle’s electrical systems will lose power, and the car may not be able to start.

Furthermore, times of too much current can wear out the alternator’s pulley quickly. Meanwhile, the alternator belt can also burn out prematurely due to too much friction.

The fuse will likely blow if the electrical system is overtaxed. This of course is due to over-stimulation. This can create a short circuit and a dead battery.

In short, an overexcited alternator can cause a range of issues. It can damage the components it powers, and the alternator itself.

To avoid these issues, it’s better to install a quality alternator. Also, ensure to keep it appropriately charged. Doing so helps protect your car from expensive repairs down the line.


A self exciting alternator is far better than a regular alternator. The advantages of 1 wire alternators must be considered. Its high resistance to damage and efficiency are exceptional.

1 wire alternators are undoubtedly worth it. If you were wondering, “How does a one wire alternator work?” Virtually all the details you need about the component have been exposed above.

However, since as using a self exciting alternator is powerful, you must take note of the pros and cons. Also, beware of the outcome of overexciting an alternator to avoid unexpected problems.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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