Komatsu is a pioneer in bringing SR (Switched Reluctance) technology into earthmoving vehicles.

We introduced SR into our surface wheel loader products more than two decades ago and have taken the technology to the next level with our KESS (Kinetic Energy Storage System) deep energy storage. The SR Hybrid Drive system captures and utilizes regenerated energy, reducing a machine’s overall fuel consumption by up to 45 percent. The KESS unit provides a larger storage capacity for regenerated energy, supplementing engine power to enhance machine acceleration, which reduces the effects of engine turbo lag, dramatically improves cycle times and results in fewer diesel emissions.

Understanding how SR technology works

The process to capture the regenerated energy begins when diesel energy is converted to electric energy through a SR generator, which provides power to the motors to make the wheels move. When the operator eases off the accelerator, the demand for diesel stops but machine momentum keeps the motors rotating. At this point, the motors become generators, supplying energy to the KESS system. When the operator hits the pedal again, the KESS supplies the stored energy while the engine simultaneously supplies diesel energy. The result is the equivalent of a 400hp engine being bolstered by an additional 550hp.

To make this possible, our engineers investigated ultra-capacitor energy storage along with battery storage. Compared to other motor technologies, the SR hybrid drive’s high-speed capability made SR kinetic energy storage feasible and more favorable against other available energy storage devices. 

Rotor/stator design means increased torque

The SR hybrid drive system design ensures that there are always rotor lobes approaching or departing fixed stator coils, resulting in increased torque.

Rotor highlights:

  • Less impact stress on gearing and high torque-to-inertia ratio means faster response
  • Lower switching frequency as compared to AC systems, resulting in longer power electronics and motor insulation life
  • Simple rugged design made up of a stack of electrical steel laminations
  • No windings, rotor bars, magnets, or contact of any kind
  • Cool running, since losses are concentrated in the stator

Stator highlights:

  • Short end turns permit very high torque/volume ratio for an electric drive
  • Independently wound coils have no overlap areas
  • Good thermal management since losses are easily dissipated though the outer circumference

Incorporated into multiple product lines

Our SR technology is now incorporated into multiple products lines:

  • Hybrid shovels
  • Gen 2 surface wheel loaders
  • Hybrid loaders

Millions of hours of operational experience

With decades of experience, we now have more than 150 surface wheel loaders using SR around the world. That means millions of hours of cumulative operation and tens of thousands of individual component operational hours.

Building on our experience, we’ve developed advanced SR control algorithms to optimize efficiencies in applying toque to the ground, controlling wheel slip to minimize tire wear and significantly reducing fuel burn. We also have incorporated decades of mining duty traction motor design knowledge to ensure our motor and generator designs are rugged, reliable and up to the task of achieving long life in the tough mining environment.