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How can a vacuum cleaner say it's 3 hp, yet only be rated at 1200 W since 1 hp is ~750 W?

The product description says it has a "3 horsepower motor" and that 3 hp is the peak.

ocrdu
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g491
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3 Answers3

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They're lying to you, vacuum cleaner motors spend most of their time running at near peak power. (when you block the hose and hear motor go faster it's using less power)

1300W universal motor, about 80% efficient, about 1.5 horsepower.

Maybe it's a 3HP motor in some other application (like driving a mechanical load), but driving a centrifugal blower its max load will be with a clear air path.

Jasen Слава Україні
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In the United States wet/dry vacuums cleaners (typically called Shop Vacs) are rated using horsepower. This horsepower rating is not the actual power output of the motor. It has no physical meaning and can ONLY be used to compare with other vacuums.

It is NOT the 1 second or 6 second or 15 second or 30 second peak power. There is absolutely no way you can connect a 3 horsepower vacuum cleaner motor to a dynamometer and measure 3 mechanical horsepower at the shaft or output. It is not even based on stall torque * no-load speed. It is basically a meaningless number, except that a 5 HP vacuum from Brand A will probably be more powerful than a 3 HP vacuum from Brand A.

user57037
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    I have to wonder why that's allowed under advertising laws. – Hearth Oct 01 '22 at 01:01
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    Why do your think they state "3 horsepower motor" and that 3 HP is the peak? https://a.co/d/ewU93nb - thanks – g491 Oct 01 '22 at 01:38
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    I think all the vacuum cleaner makers are stuck. If they advertise actual power, then they will appear weaker than competitors advertising according to vacuum cleaner fantasy horsepower. Some vacuums do list static pressure and flow at zero back-pressure, both of which are useful. – user57037 Oct 01 '22 at 02:00
  • https://www.youtube.com/watch?v=oM4SMQGMFz8 – user57037 Oct 01 '22 at 02:12
  • I guess this answer is US-centered? In the EU vacuum cleaners are rated with their proper maximum electric input power, which (for household devices) is limited to below 900 W since several years. – asdfex Oct 01 '22 at 10:02
  • @asdfex yes. In the US, wet/dry vacuum cleaners (often called shop vacs) are usually rated by "horsepower." Home vacuum cleaners are not usually rated by horsepower. I will update my answer slightly to make the scope more clear. – user57037 Oct 01 '22 at 17:02
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This is probably peak power, which for universal motors can easily be two to three times nominal power rating. Motors and transformers generally can be overloaded for short time duty cycles based on I2t heating of the winding resistance, so for example:

1x continuous

1.4x 50% duty cycle (30 seconds ON, 30 seconds OFF)

2x 25% duty cycle (15 seconds ON, 45 seconds OFF)

3x 10% duty cycle (6 seconds ON, 54 seconds OFF)

https://electricalmag.com/universal-motor-characteristics-speed/

https://www.routerforums.com/threads/peak-horsepower-vs-real-horsepower.26428/

Transistor
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PStechPaul
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  • So the rating has nothing to do with operating performance; it indicates the safety cushion for motor damage (the motor would burn out at 2250W, but operates at only 1200W, so you don't need to worry about burning out the motor with normal use)? – fixer1234 Oct 01 '22 at 19:14
  • The rating is probably bogus marketing hype, and for a vacuum cleaner the motor will never run at any more than actual input power (1200W), which occurs when moving the maximum amount of air. It is unknown if the motor is actually rated higher, and I doubt that manufacturers would use a motor with higher rating than needed. I think most vacuum cleaners fail due to clogged rotors, dry bearings, and insufficient cooling. – PStechPaul Oct 01 '22 at 22:26