How to choose the right alternator for a diesel generator of Green Power?- Part 1

In the modern world, diesel generators are essential for many industries, businesses and households. One of the most important components of a diesel generator is the alternator, which converts mechanical energy from the engine into electrical energy. Choosing the right alternator is essential for the correct and efficient operation of the generator.

What is an alternator and how does it work?

An alternator, also called a synchronous generator, is an electrical machine that generates alternating current (AC) by rotating a rotor in a static magnetic field. The main components of an alternator include:

Rotor – the rotating part that creates a magnetic field.

Stator – the stationary part in which electric current is induced.

Rectifier and voltage regulator – electronic components that regulate the output voltage and stabilize the operation of the generator.

When the diesel engine drives the alternator rotor, voltage is induced in the stator, which is supplied to the electrical network or directly to consumers.

Main types of alternators

When choosing an alternator for a diesel generator, it is important to know the main types of alternators:

1. Synchronous alternators

The most common type. They operate at a constant frequency and synchronize their rotation with the frequency of the electrical network. They offer high stability and the possibility of parallel operation. Their advantages are – high efficiency, suitable for backup and main power supply, can operate in synchronization with the electrical network.

2. Asynchronous (induction) alternators

Less commonly used, usually in simpler systems. They require an external excitation source and cannot operate independently. Their advantages are lower cost, simpler construction, low maintenance requirements. Their disadvantages are lower efficiency, not suitable for all applications.

Main factors when choosing an alternator

1. Power (kVA or kW)

The choice of an alternator begins with determining the required power. It must be considered:

The total load of the consumers.

The type of load (resistive, inductive, capacitive).

Starting currents of electric motors.

Golden rule: The alternator must be able to provide at least 20-25% more power than the total expected load to absorb the peak currents when starting machines.

2. Voltage and frequency

Depending on the application, we must choose the appropriate one:

Voltage: 230V (single-phase) or 400V (three-phase).

Frequency: 50 Hz (in Europe) or 60 Hz (in some other regions).

The alternator must be compatible with the electrical installation and the devices it will power.

3. Type of load

Loads can be:

Resistive (heating, lighting) – easier to power.

Inductive (motors, compressors) – require higher starting power.

Electronic (computers, UPS) – sensitive to voltage and frequency variations.

An alternator with appropriate regulation and stabilization must be selected to avoid damage or interruptions.

4. Excitation system

There are two main types:

With rings and brushes – cheaper, but require maintenance.

Brushless – more reliable and longer lasting, but with a higher initial price.

Brushless alternators are preferred for long-term use, especially in industrial conditions.

5. Insulation class

Denotes the resistance of the insulation to high temperatures. The usual classes are:

Class B – up to 130°C

Class F – up to 155°C

Class H – up to 180°C

The higher the class, the more resistant the alternator is to long-term operation.

6. IP protection

Indicates the degree of protection against dust and moisture. For generators used outdoors or in dusty environments, IP 23 or higher is recommended.

With a well-chosen alternator, the diesel generator will operate stably, provide quality power supply and last over time. An investment in a suitable alternator not only pays off, but often saves significant costs from breakdowns, loss of production or interruption of work.