There seem to be many misconceptions (and reasons) regarding the direction of rotation of ceiling and best table fans in opposite directions. here we know about What are the main difference between a ceiling fan and table fan?
In fact, in many related works, the term “engine” itself has been misused and can be understood by any technician in the art.
What are the Main difference between a ceiling fan and table fan?
Technically, both types of motors operate on the principle of a single-phase induction motor. A single-phase motor has a pair of stationary windings (called a stator) in quadrature with each other and designed to transfer currents with a phase difference of 90 degrees, ideally from a power source. Single-phase alternating current.
The other part of an induction motor is the rotor, a rotating part that can be thought of as a group of conductors in which currents are induced. The currents flowing through the stator windings create a magnetic field, for example rotating clockwise.
A sequence of electrical events causes the rotor to follow the magnetic field as if it were being caught. that is, the rotor also rotates clockwise. If a switch is provided to change the direction of the current in one of the stator windings, the magnetic field, and therefore the rotor, rotates counterclockwise.
In a ceiling fan, the stator with its winding is surrounded by a rotor to which the fan blades are attached. The ceiling fan is installed close to the ceiling so that depending on the direction of rotation, it can push air downstream (usually used as a fan) or it can be used to draw hot air upward. (as in winter, especially in cold countries) in reverse
direction of rotation with control switch.
Clockwise or counterclockwise relative. When viewed from below, if the ceiling fan rotates counterclockwise, when viewed from the ceiling, it is clockwise.
In fact, this convention has an interesting history (Sujit K. Biswas, Jadavpur University, April 4, 2014, ResearchGate | Share and Discover Research)
When DC motors were previously used for AC motors, the DC motor switch and brushes were placed in the ceiling for easy access.
and maintenance. More importantly, with this setting, the DC motor will rotate clockwise from the end of the manifold (end of the ceiling) according to the right screw convention, the direction of rotation of the tap to stop the flow of water, etc. Simply put, a person on the ground will look in a counterclockwise direction. This agreement continued even after the replacement of DC motors with AC motors.
Pretty much everything about a ceiling fan is technically true for a desktop fan. However, it is said that instead of the side of the collector facing a vertical wall at the back (ala a ceiling for a ceiling fan), for the sake of elegance, it was turned upside down, as if facing the viewer from the side. face.
This changed the direction of rotation from the point of view of the observer to clockwise. Even after replacing DC motors with AC motors, the same agreement is still followed.
An AC motor, as opposed to a DC motor, is a mechanically symmetrical motor considering its main working parts, and each end can be designed to be end-user (like fan blades) using a suitable mechanical design. Therefore, in theory, a desktop fan can only be designed with a suitable mechanical design for counterclockwise operation.
Electrically ceiling and table fans are similar (both have stationary windings receiving AC power, and both have a rotor to induce currents and operate an induction motor, and do not affect the direction difference.