Truth About Horsepower
Subject: Peak Horsepower (PHP)
Many manufacturers of vacuums and shop vacuums are marketing them as 4 to 5 Peak Horsepower (PHP). But no matter what you call it, PHP, HP, or horsepower, it's all just horse hockey when it comes to the performance of a vacuum cleaner.
To put it into the simplest terms:
· When it comes to vacuum cleaners, horsepower is a bogus, fictitious number having no relationship to the performance or cleaning ability of the product.
· Horsepower is not based upon the normal operating current of the motor. It is calculated using the maximum in-rush current. In-rush current is the current a motor sees when first started up, before the effects of winding inductance come into play. A motor with a nominal operating current of 12Amp can easily have an in-rush current of 30Amp to greater than 50Amp, depending upon the windings. It typically lasts for only 8 to 12 milliseconds (0.008 to 0.012 seconds). Some manufacturers attempt to maximize the in-rush current by conditioning the motor at very low temperatures (as low as -20F). This lowers the motor resistance, thus increases the in-rush current.
· Power is equal to volts times amps. Even ignoring the efficiency and power factor of the motor, a motor with a nominal 12Amp current @ 120Volts will only produce 1, 440 Watts. There are 745.7 Watts per horsepower. Thus, under the best of conditions, the motor will only produce 1.9 hp. A motor touting 4 hp would have to produce 2983 Watts. With that power, the motor would be drawing 24.9 Amps. Horsepower is determined for the motor (without any fan blades), not the vacuum cleaner system, and does not take into account any normal system losses (air leaks, restrictions, piping and the like).
This became such an issue in the late 1980s and early 1990s that Underwriters Laboratories and the Canadian Standards Association put wording into the vacuum cleaner standard prohibiting horsepower from appearing on the products electrical rating label.
Horsepower has no bearing on the performance of the product. It's just horse hockey!