Explaining Vacuum Motors - and how to measure suction




The power and efficiency of a vacuum motor is one of the most important aspects regarding the overall performance of a vacuum cleaner. The motor converts electrical power into mechanical power in the form of sealed vacuum and airflow. Measuring and rating a vacuum motor's capability to produce this mechanical power is one of the most misunderstood aspects of vacuum cleaner technology.

Below is a few terminologies used to measure the power of the motor:

Air flow

Air flow is usually stated in Litres per Second (L/s) when measured for a vacuum cleaner motor. While the air flow rating is not a direct rating of the power of the suction motor, it is affected by its suction. The air flow rating is typically obtained by measuring the air flow through the power unit with the limit of a 2" opening simulating resistance to air flow. The air flow is relative to the amount of sealed vacuum produced by the motor and proportional to the total resistance to air flow within the system. There are many things that affect the air flow in a vacuum cleaner which are not reflected in the air flow rating. In addition to the resistance in the vacuum, there is resistance caused by air turbulence in the hose and tubing, restriction where the cleaning nozzle contacts the floor, as well as increased resistance within the filtering system as the unit fills with dirt. Therefore it is important to compare the sealed vacuum along with the air flow when comparing vacuum cleaners.


Horse Power

Historically Horse power is most common ratings for the power of a ducted vacuum motor (one horsepower equals 550 ft lbs. per second , which is the power needed to lift 550 pounds one foot off the ground in one second and now often defined as approximately 746 watts). The accuracy of these ratings is often uncertain, however, the significance of these ratings is meaningless because one 2000 watt motor may be very efficiently designed whilst another 2000 watt motor may be poorly designed and not actually produce the same mechanical power.
a typical customer simply wants a good ducted vacuum system and air flow (measured in litres per second) is the true measurements of the performance of a vacuum motor.
Some manufacturers have replaced horse power, wattage, sealed vacuum and air flow ratings with a different rating called Air Watts in an attempt to rate the output power of the vacuum cleaner instead of the input power, a measurement most people don’t understand.



The best way to obtain Wattage ratings is by multiplying the amperage drawn from the power point by the voltage (240 volts in Australia) of the power source. It is only a measurement of the input power of the motor. Wattage ratings are often used by some manufacturers to make it harder and more confusing when trying to compare their products with competing ones which use Air Watts or other ratings. For example, a manufacturer can create a vacuum cleaner with 2400 watts printed on it and name this vacuum “super suction force”. The reality is that this vacuum although it has 2400w can have less suction than a 1200w motor. The difference is in the design of the motor and that creates airflow.

In summery it is often assumed that the greater the input power the greater the cleaning effectiveness but this normally isn’t the case. The number of fans and blades in a motor can dramatically affect the vacuum cleaner performance. Some vacuum motors have three fans pulling in series to provide plenty of air flow for long pipe runs. Some newer motor designs produce high sealed vacuum and air flow with only one fan, utilising tapered fan technology.