We’ve Got the Right Step-by-Step Equation to Solve for That

Brake horsepower (BHP) is an important number to know because it tells you how much force you need to stop the motor and, ultimately, what size motor you need to drive your industrial fan application. The video above and copy below outline exactly how to calculate brake horsepower for a fan motor with a simple equation.

How to Calculate Brake Horsepower for a Fan Motor

As long as you know your fan specifications and the right constants, there’s nothing complicated about calculating BHP. It’s a simple process of multiplication and division. Here are the numbers you need to know:

  • Voltage (Volts or V) is typically a region-specific constant determined by the power source. In the United States. Industrial applications commonly use three-phase 480V power at the source, which translates to 460V at the motor. Learn more about that here.
  • Amperage (Amp) Draw is a measure of power the industrial fan or blower uses to do its job, calculated by dividing the watts by the voltage.
  • Motor Efficiency is a ratio calculated by dividing the motor shaft output power by the electrical input power, usually between 50-100% – find it on the motor nameplate and datasheets.
  • Motor Power Factor is a characteristic of the motor in your application stated as a percentage less than 100 and usually designated on the motor nameplate.
  • Numerator Constant when using voltage and amps is always 1.732.
  • Denominator Constant when using voltage and amps is always 760.

The equation is as simple as it gets. Multiply the first five figures and then divide by the Denominator Constant. Or, put another way, you could divide the Numerator Constant by the Denominator Constant and then multiply the resulting constant by all of the variables.

Once you’ve mastered how to calculate the brake horsepower of a fan motor, you can easily use it to determine what size motor you need for any industrial fan application. But if you forget the calculation, you should also be able to find BHP in the specs from your fan manufacturer.

Hear About Calculating BHP from an Application Engineer

Chet White, Senior Application Engineer / Sales & Marketing Manager, outlines how to calculate the brake horsepower of a fan motor using a simple whiteboard drawing in this 3¼-minute video.

To ask questions, get more details, or discuss your application, reach out and connect with one of our application engineers.

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