Airflow is everything when speaking of a vacuum cleaning machine.  Without sufficient airflow a vacuum cleaning machine is of no value.  The loose particulate compounds found on floors and in carpets are only removed if there is airflow present.  How a manufacturer engineers and manages airflow will change depending upon which style of vacuum cleaning machine is being produced.   An upright machine like a Kirby or a Hoover has a short air path, whereas an upright machine with a detachable hose and accessories has a convoluted path.  A  pull-behind or towed machine has a long air path and a canister upright machine like dyson has a short clean path.

The path air takes through the machine is critical to the overall performance of the machine.  A path with lots of turns and hoses will impede airflow greatly, whereas a path that is short and has few turns will impede air flow to a lesser extent.

All vacuum cleaning machines must have a power plant.  The power plant is where energy enters the machine to create the air pressure vacuum, which in turn generates airflow.  The device that generates the vacuum is an electric motor.  An electric motor has many characteristics that define it’s capabilities.  The National Electrical Manufacturers Association (NEMA) has identified those characteristics and specified that all motors have motor specification data listed on an individual nameplate on the motor.

NEMA is an association and not a regulator or government entity.  Consequently, it cannot require that all manufacturers label their motors with the items they have suggested.  Many manufacturers only provide a few items on nameplates and then provide more extensive information on a web site where the model of the motor is listed.

The  ability of a motor to provide a mechanical force is presented as horsepower.  Mr. James Watt an inventor who worked primarily with steam engines, established a method of measuring mechanical force and related force to the abilities of a horse in performing similar mechanical tasks.

After considerable experimentation, Mr. Watt established an average horse could work at a rate of 550 foot-pounds per second (550 ft-lb/s).

Using a bit of math to ramp the equation up to a full minute, the average horse could work at a rate of 33,000 foot-pounds per minute.  And this became the standard by which we measure horsepower today.

1 HP = 33,000 ft-lb/min

Mr Watt, having moved on from steam engines to electric motors,  now needed to sell his electric motors and provide a measure to differentiate one motor from another.  So, he established a new measurement of “energy used”.  This measurement is called the watt after Mr. Watt.  It is the measure of one horsepower as it relates to energy used by an electric motor.  Mr. Watt established that 1 horsepower equaled 33,000 ft-lb/min and that was the same as 746 watts of energy used by an electric motor to perform the same task as an average horse.  Therefore, 1 HP = 746 watts.

All electric motors have a duty cycle.  This term identifies the duration of time a motor is designed to operate at baseline RPM.  The values ore: Continuous, Intermittent, periodic, short-time, and varying.  For the most part, vacuum cleaning machines are designed to have a duty cycle of varying duty.  This is where the motor operates at varying loads at varying intervals of time.  Some specialty machines (toner vacuums) that are compact and operate at high RPM are designed for intermittent duty, where the motor operates at full load and then needs a rest period before continuing.  These latter machine types become very hot if not given a rest period.

Service Factor is a measurement of how much an electric motor can be overloaded.  This is an interesting measurement in that it determines longevity of the life of a motor.  A motor with a service factor greater than one means the motor is designed to operate at RPM and torque values greater than the baseline speed at load.  This means the motor will operate at cooler temperatures and last a long time.  This value is rarely specified on the sides of the box, but is is a factor in the machine running at a cool temperature.

Voltage Rating for machines purchased in the U.S. or Canada will always be 120 Volts.  Some machines will state their voltage rating to be 120/230 Volts.  These machines can operate in both North America and Europe.  The frequency in North America will always be 60 Hertz.  Some machines will list the frequency as 50/60 HZ.  These machines can operate in Europe as well as North America.

Maximum Temperature and Motor Efficiency are two other components used to describe a motor.  Maximum Temperature is rarely provided a purchaser of a machine as is Motor Efficiency.  Temperature relates to the operating temperature of the machine during normal loads.  This value should not be excessive, as heat destroys motors.  To apply a field test in evaluating machines, turn on the machine and wait 5  minutes.  Feel the exhaust air.  Placing a hand in the exhaust airflow path should be comfortable and not overly hot.

All electric motor have inefficiencies when converting electric energy (watts) into kinetic energy (RPM).  Unless the manufacturer displays their Motor Efficiency, the consumer will have no idea what the value is.  This information is provided as informative, but not a decision-making value.

Understanding the electric motor in your machine is just another part of making an informed decision when acquiring a vacuum cleaning machine.

The fan assembly on most power plants is a flat disc with blades rising from a solid surface.  The blades can either be straight or can be slightly curved to increase the creation of a vacuum and lessen turbulence.  The variables in the fan assembly design include the surface area of the impeller blade and the number of blades.  By increasing the number of blades, manufacturers increase the amount of air that is in contact with a surface.  An increase in surface area allow more kinetic energy to be transferred to the air and as a result a greater vacuum is established causing greater airflow.

The fan assembly works in concert with the fan motor and together they represent the power plant.  The fan assembly design has a cowling surrounding the fan blades.  The cowling separates the low air pressure vacuum from the high pressure air or exhaust.  Without the cowling it would be difficult to generate any significant air pressure vacuum and resultant airflow volume.

The cowling is a shroud of material either plastic or metal that sits just beyond the edge of the rotating fan blades.  It surrounds the entire pathway of the blades as they rotate to generate an air pressure vacuum.  The cowling insures that limited amounts of air can make their way back to the underside of the fan blade, thus negating the ability to generate an air pressure vacuum.

The power plant must be of sufficient size to spin a circular set of angled blades to generate a pressure differential that is greater on one side of the blades than the ambient air pressure at the center of blades on the power plant motor.  This creates the airflow necessary to operate the machine.  One side of the fan blades has a vacuum and the other has an excess of air at higher pressure.

Depending on the intended size of the vacuum cleaning machine and it’s intended use, manufacturers will vary with the size of the blades and the rotation speed of the motor.

Manufacturers are continually working with the sound levels of their vacuum cleaning machines to reduce the operating noise.  The problem is that increasing the RPM of the power plant increases the noise level of operating the machine.  This is particularly noticeable in smaller more portable machines.  Apart from the noise of running an electric motor, The only other noise generator is the air itself.

To generate sufficient airflow, manufacturers need to increase the rotation speed of the small fan assembly to generate enough vacuum to have sufficient airflow.  In doing this, the machines become very loud.  The sound generated from a fan assembly comes from air collapsing back together after a blade has cut through the air from spinning.  The more a blade cuts through the air the louder the noise from air collapsing back together.

To address operating noise, manufacturers have engineered a number of solutions to include: added noise insulation, increased density of materials surrounding the power plant, placing the dust collection behind the power plant, sound absorption coatings, and added sound absorbing grommets to bolts.

You  might also be interested in:

ALNV discovery.  A site with diverse topics and opportunities for learning.