What does the Alternator do in a Diesel generator?

diesel generator alternator

Many people are not clued up when it comes to mechanical elements, alternators, generators and such. We just expect things to work as they should do, and that is understandable. You might believe that the battery powers the electrics when it comes to a diesel generator. The battery side of things only provides the electricity to start the generator, and not what actually creates the power. In fact, the alternator is what created the power in order for the diesel generator to run. Enabling all components to operate and also to put the electrical charge back into the battery itself. 

The alternator within your diesel generator is an important element of it. The alternator is responsible for converting the mechanical energy that is then used to power the generator, or whatever the generator is actually being used for. Commonly found in businesses operating large premises. But not everyone is totally sure on how the alternator works, and what it does when it comes to the diesel generator you have grown to rely on. This article will hopefully give you more clarity on this.


How are alternators produced?

For the most part, alternators are relatively small and lightweight. They are roughly the size of a coconut, the alternators found in most diesel generators will be constructed using an aluminium outer housing, as the lightweight metal does not magnetize. This is important since aluminium dissipates the tremendous heat generated by producing the electrical power and since the rotor assembly produces a magnetic field.

If you closely inspect an alternator, you'll find it has vents on both the front and backside. Again, this aids in heat dissipation. A drive pulley is attached to the rotor shaft on the front of the alternator. This can help to operate the diesel generator. 


The role of the alternator in more detail 

Some would say that the battery power is the strongest component of a diesel generator but this is where people can get confused. The alternator is the main component that keeps the diesel generator running smoothly. The alternator is responsible for converting the mechanical energy provided by the battery into the generator itself. 

The alternator works together with the battery to supply the power to the diesel generator. The output of an alternator is the direct current. When the alternator pulley is rotated, the alternating current passes through a magnetic field, and that is where the electrical current is generated. This is then converted into direct current via the rectifier. 

Alternator components include:

  • Regulator - The voltage regulator controls the amount of power distributed from the alternator to the battery in order to control the charging process. Regulators are designed with different functions and work depending on their specification.
  • Rectifier - The rectifier is used to convert current from alternating current (AC) to direct current (DC) during the charging process.
  • Rotor - The rotor is the spinning mass inside the alternator that rotates via the pulley and drive belt system. The rotor acts as a spinning electromagnet.
  • Slip Rings -The Slip rings are used as a means of providing direct current and power to the rotor.
  • Slip Ring End Bearing - The bearings are designed to support the rotation of the rotor shaft.
  • Stator - The stator consists of several coils of wire wound through an iron ring. The stator sits outside the rotor when a magnetic field is created the electrical current is made.
  • Drive End Bearing - The bearings are designed to support the rotation of the rotor shaft. 
  • Pulley - The pulley is connected to the rotor shaft and the drive belt system. Rotation created by the engine the drive belt system turns the pulley beginning the charging process.


Brands of alternator

There are some common brands of alternator that you will find on the market today that can help operate a diesel generator. They include DB Electrical and Bosch. There are many articles online that work on specific reviews of alternators that could help you find the right one for the job. 


What to notice if things aren’t right with your alternator?

There are things that you should be looking out for when it comes to your diesel generator and within the alternator itself. There are some signs that you can distinguish that will help you to understand when your alternator within the diesel generator may need fixing. These include:

  • Overheating 
  • Condensation
  • Short circuits
  • A burning smell


What you should be checking for when it comes to the alternator in your diesel generator?

There are things that you can keep an eye on to help you ensure that your diesel generator and the alternator within it are working smoothly. It is always going to be worthwhile to ensure that you have your diesel generator and the alternator within it checked. A good tip is to consider every six months as a good starting point unless you notice any of the above signs. However, upon checking your diesel generator here are the things that should be checked. These include the following things:

  • Ambient temperature
  • Winding, rotor, exciter and PMG insulation resistance
  • Temperature sensors
  • AVR and PFC settings
  • Auxiliaries function
  • Controls synchronization
  • Air inlet temperature
  • Air filter

After 5 years there are other factors that may need to be checked to ensure that your diesel generator and alternator are working as they should be. The following things should be looked at:

  • Sealed bearings
  • Anti-condensation heater
  • Diodes and varistors
  • Air filters

How has the alternator changed over the years?

There has been a lot of advancement in technology that has meant that alternators have changed a lot in the last 50 years. Originally, alternators were used to generate a current which was controlled by an external regulator. There was an introduction in the 1990s that meant a regulator internally could enhance the way the alternator operates. 

Let’s hope that sharing this article will help you understand what an alternator does in your diesel generator and to ensure that you take good care of it, now and in the future.