Single Bearing vs Double Bearing Alternators

A Simple Guide for Generator Buyers

When choosing a diesel or gas generator set, you may see terms like single bearing alternator or double bearing alternator.
They sound technical, but the idea behind them is actually quite simple.

It all comes down to how the industrial generator alternator rotor is supported.

What’s the Real Difference?

Single Bearing Alternator

A single bearing alternator has one main bearing inside the alternator.
The other end of the rotor is supported by the engine flywheel.

In simple terms, the engine and alternator work as one compact unit.

Why it’s popular:

• Simple and robust structure
• Compact design
• Lower cost
• Widely used in industrial generator sets above 15 kW

This is the most common solution in the generator industry today.

Double Bearing Alternator

A double bearing alternator supports its rotor entirely by itself, using two bearings.
The engine only provides power through a flexible coupling, without carrying the rotor load.

Think of it as a more independent setup.

Why it’s used:

• Better tolerance for alignment errors
• Less mechanical stress between engine and alternator
• Useful in special installation conditions

The structure is slightly more complex and usually comes at a higher cost.

Does Bearing Type Affect Generator Performance?

For most industrial applications, the answer is no.

When properly designed and installed, both single and double bearing alternators can deliver:

• Stable voltage
• Reliable frequency
• Long service life

What really matters more is:

• Alternator brand and build quality
• Cooling and insulation design
• Rotor balancing
• Proper assembly and installation

Which One Should You Choose?

• Standard industrial projects
  → Single bearing alternators are proven, reliable, and cost-effective
• Projects with difficult alignment or special mounting conditions
  → Double bearing alternators offer more flexibility

In practice, bearing type is a structural choice, not a performance shortcut.

The OWELL Generators Approach

At OWELL Generators, diesel generator alternator selection is never one-size-fits-all.
We match engine, alternator, coupling, and application conditions as a complete system.

Whether using single bearing or double bearing alternators, every generator set is engineered for:

• Stable operation
• Long-term reliability
• Real-world industrial performance

Reliable power starts with the right structure — and the right manufacturer.