How to choose a suitable alternator for Grupel diesel generator? – Part 2

The alternator is the key component in a diesel generator, responsible for converting the mechanical energy generated by the engine into electrical energy. The correct choice of alternator is critical to ensuring reliable and efficient operation of the entire system.

1. Alternator selection criteria

1.1 Compatibility with the diesel engine

The alternator and engine must operate in sync.

Specify: revolutions per minute (usually 1500 rpm for 50 Hz).

Ratio between mechanical and electrical power – important for efficiency.

1.2 Type and nature of the load

Are motors, UPSs, computers, lighting or a mixed load being powered?

For non-linear loads, alternators with increased resistance to harmonic distortion are recommended.

1.3 Operating conditions

Temperature, humidity, altitude – affect cooling and performance.

For harsh conditions: choose an alternator with a higher protection class (IP-class).

1.4 Cooling method

Air or water cooling.

For high power: water cooling provides more stable operation.

1.5 Availability of AVR (Automatic Voltage Regulator)

Required to maintain stable voltage.

For critical applications: look for an AVR with precise regulation (±1% or less deviation).

2. How to make the right choice – step by step

Step 1: Determine the required generator power

Add up the power of all electrical consumers, add a reserve of 20–30% for future expansions.

Step 2: Select an appropriate diesel engine

The engine must provide sufficient mechanical power to power the alternator at full load.

Step 3: Select an alternator compatible with the engine

Pay attention to compatibility in terms of speed, engagement, torque.

Check manufacturers’ catalogs for compatible models.

Step 4: Determine the type of alternator you need

For critical applications – choose a brushless synchronous alternator with AVR.

For standard needs – a basic model can also be used.

Step 5: Consider the environment

Check if the alternator is designed for outdoor installation, high humidity, dusty environments, etc.

3. Leading alternator manufacturers

Some of the most reliable and common brands:

Stamford (Cummins Generator Technologies) – industry standard.

Mecc Alte – Italian manufacturer, popular in Europe.

Leroy Somer – French brand, known for its high efficiency.

Marathon Electric – preferred in the USA.

Linz Electric – modern solutions for small and medium generators.

4. Common mistakes when choosing an alternator

Underestimating peak loads – leads to overload and damage.

Choosing a cheap model without AVR – risk of damage to sensitive equipment.

Mismatch between engine and alternator speed – leads to unstable frequency.

Using a single-phase alternator when a three-phase load is needed – inefficient and risky.

Choosing an alternator for a diesel generator is not just a matter of power compatibility. Many technical factors must be taken into account – from type and efficiency to voltage stability and brand reliability. A well-chosen alternator will guarantee trouble-free and long-term operation of the generator, regardless of load conditions and environment.