Horsepower vs Brake Horsepower
Horsepower is a unit of measurement of power, which is the time rate of work being done. The term was coined by Scottish engineer James Watt in the late 18th century as a reference to the output of steam engines, but later expanded to include the output power of engines, as well as turbines, electric motors and other machinery.
More about Horsepower
The unit of horsepower has many definitions and varies according to regions too; it is considered a vague unit.
The mechanical horsepower, also known as imperial horsepower is the 550 foot-pounds per second which is approximately the same as 745.7 Watts in SI units. The horsepower unit used for rating electric motors is equal to 746 watts. The horsepower unit used for rating steam boilers is known as the Boiler Horsepower and it is equivalent to equivalent to 34.5 pounds of water evaporated per hour at 212 degrees Fahrenheit, or 9,809.5 watts.
The metric horsepower defined as 75 kgf-m per second, which is approximately the same as 735.499 watts.
In the general sense, the horsepower is the amount of energy passed as the usable work output from an engine.
More about Break Horse Power
An engine loses its generated power due to friction and other factors in gearbox, differential, alternator, water pump, and other components such as muffled exhaust system, power steering pump. Brake horsepower (bhp) is the measure of an engine’s power prior to the loss in the components noted above. The device that is used to load the engine and maintain it at a desired RPM is known as the Brake.
Upon testing the engine, the output torque and rotational speed are measured to evaluate the brake horsepower. Using the De Prony brake connected to the engine’s output shaft the performance parameters of the engine are measured. More recently, an engine dynamometer is used instead of a De Prony brake. Even though the output power delivered to the driving wheels is always less than the power output at the engine’s crankshaft, chassis dynamometer measurements are an indication to the engine’s actual horsepower delivered, the horsepower after the losses in the auxiliary components.
What is the difference between Horsepower and Brake Horsepower?
• Horsepower is the usable energy / work output rating of an engine at the terminal components of the machine, such as the power at the driving wheels of a vehicle.
• Brake horsepower refers to the energy output at the crankshaft before the losses in the subsequent components and operations.