What is Horsepower and Brake horsepower ?

Brake horsepower

Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump etc. Brake refers to a device which was used to load an engine and hold it at a desired rotational speed.During testing, the output torque and rotational speed were measured to determine the brake horsepower.

Differing definitions “horsepower":

●       The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to 745.7 watts.

●       The boiler horsepower is used for rating steam boilers and is equivalent to 34.5 pounds of water evaporated per hour at 212 degrees Fahrenheit, or 9,809.5 watts.

●       One horsepower for rating electric motors is equal to 746 watts.

The mechanical power is measured by the rate at which work is done. On the other hand, electrical power is measured by the rate at which electrical energy is transformed.

-In terms of the power generation, mechanical power is generated by the mechanical equipment like piston-cylinders, turbines, etc and the electrical power is generated by alternators.

The concept of power is same in the context of mechanical as well as electrical engineering applications. The unit Kw is an electrical as well as mechanical power unit. Though the basic concepts remain the same, the form of the governing equations in case of the mechanical power is different than that of electrical power. Moreover, in mechanical engineering application itself, different equations are used for calculating power for hydraulic, thermal, and rotational systems.                                                

Power output / Power input * 100 = %Efficiency

For instance, 746 watts is equivalent to one horsepower. If an electric motor were 100% efficient, a 1HP motor would only draw 746 watts of electricity. Look in any motor catalog, and you will see that typical 1HP motors draw around 1100 watts. So:

(746 / 1100) * 100 = 67.8%

The example motor has a 68% electrical efficiency. You can apply the same formula to any electrical device - heaters, amplifiers, transformers, etc.