What is Windage Losses in Electrical Machines?

What is Windage Losses?

Windage losses are the amounts of energy lost in an electrical equipment as a result of friction between moving elements and the air around them.

These losses happen in spinning electrical equipment like

  • Motors,
  • Generators, and
  • Transformers.

As the components pass through the air, they encounter resistance, causing some of their energy to be lost in the form of heat.

Windage losses in electrical machinery can be caused to numerous sources, including:

  • Stator & Rotor
  • Cooling Fan
  • Bearings & Shaft

Stator & Rotor

As moving parts, including the rotor and stator in a motor (or) generator, they adhere to air resistance. Frictional losses occur as a result of this resistance, transforming portions of the mechanical energy into heat.

Cooling Fan

To regulate temperature, machines frequently use cooling fans (or) ventilation systems. These rotating fans in the air provide additional windage losses.

Bearings & Shaft

The rotating shaft & bearings are also subjected to air resistance during their travel, resulting in further energy loss.

How do you calculate windage loss?

The windage loss of a smooth cylindrical rotor will be calculated using the theoretical equation below (windage loss formula):



ρ – Density of Fluid

r – Radius of Rotor

Cd – Skin friction Co-efficient

What is windage loss in DC machine?

Windage losses are caused by air inside the machine’s revolving coil. Eddy current losses are related to the square of speed.

Windage losses cause noise and vibration, reducing motor performance and comfort. To reduce windage losses, parts should be designed with aerodynamic forms and fans with the low noise & high efficiency.

Note: Windage losses in induction devices are directly proportional to the cube of speed.

How to reduce windage losses in machine?

Windage losses must be reduced in order to increase the efficiency of the electrical machinery. To reduce these losses and increase overall efficiency, engineers frequently design equipment with the streamlined designs, employ materials with reduced friction coefficients, & optimize ventilation systems.