Introduction to electrical motorAn electric motor is a machine that can convertelectrical energy and transform it into mechanical energy. An electric motor hasa coil of wire which creates a magnetic field when the electricity flowsthrough it. The magnetic field is the region of influence of a magnet. The magneticfield is shown in figure 1.
This is known as electromagnet. In figure 2, asimple electromagnet is shown. The current is sent through the loop of the wirethat is positioned inside the magnetic field. “When current flows through a magneticfield, the charges feel a magnetic force on them at 90 degrees to the directionthey’re moving.
Because of this, the wire as a whole feels a big force. Andthis force causes the loop of wire to move; electrical energy has been changedinto movement.” (Wood, David 2017). Figure 1,Drawing magnetic field diagram (Unknown Author (2014) Drawingmagnetic field diagram. Figure 2, Electromagnet (Wood, David 2017). 2. Ceiling fans A ceiling fan is a mechanical fan that usuallyworks through electrical power. It is used on the ceiling of any room.
Ingeneral, the ceiling fan rotation power is typically slower than other types offans such as electric desk fans. In the figure 3, an illustration of a ceilingfan is provided. They tend to work on induction motors that convert electricalenergy into mechanical energy. The mechanism of the ceiling fan is that thecapacitor of the fan torques up the electric motor which allows it to run justafter a start.
The current reaches the motor and makes its path towards thecoil. The current then conducts through the wire, while the magnetic field iscreated, and exerts force in a clockwise movement, which then converts electricalenergy into mechanical energy. From this, the motor coil begins to rotate; thecoils then spin and the fan captures the motion while transferring it to the fanblades. Figure 3, Ceilingfan drawing (Jeremy2017) 2.1 Ceiling fan features There are various features that a ceiling fanhas: (1) Blade size: It is important to know what blade size would be moresuitable, depending on the room size. In figure 4, it is demonstrated that bladescome in several sizes, and measured by the full blade sweep they produce 30,42, 44, 46, 50, 52 and 60 inches. Figure 4, Ideal blade length per room size. (Sawyers,Harry 2011).
In figure 5 and 6 you can see the suggestedlengths of drop rod for ceiling fans that have a range from 9 to 13 or more. Itshows in figure 5 the right distance to install a ceiling fan for safetymeasurements. Figure 5,Sizing and locating a fan (Vandervort, Don 2016). Figure 6,Suggested lengths of drop rod for ceiling (Vandervort, Don 2016).
In figure7, we can see the rotation rule of blades; a counter clockwise rotation pushesair downward to a room and will make you feel colder whereas reverse rotationwill draw air upward to circulate hot air. Figure 7, Which way should a ceiling fan spin. (Alucard 2017). (2) Material of fan: ceiling fans can be madefrom different materials such as wood, plastic or wicker. Figure 8 shows theability of a fan through its control of it speed. In figure 9-11, the 3 type ofspeed regulators are provided. Figure 8,Fan speed regulator (Erlmarli, Khiri and others 2017). Figure 9, Conventionalfan regulator (Erlmarli,Khiri and others 2017).
Figure 10, Electronicfan regulator (Erlmarli,Khiri and others 2017). Figure 11,Capacitive type regulator (Erlmarli, Khiri and others 2017). Figure 12,Fan speed regulator.
(Erlmarli, Khiri and others 2017). For the induction motor, the variable speedinduction motor equation is presented in figure 13-14. Figure 13,Variable speed induction motor torque equation (Rayner, Robert 2017).
Figure 14,Variable speed induction motors (Rayner, Robert 2017). Figure 15 shows what is inside a ceiling fan. Figure 15, inside aceiling fan (Sawyers, Harry 2011).
2.2 Ceiling fan motor type Typically, in a ceiling fan, an AC Motor is used.It runs in a single-phase with an induction motor assembled in it. The AC motorhas two basic parts: a stator and a rotor, which are shown in figure 16. “The statoris in the stationary electrical component.
It consists of a group of individualelectro-magnets arranged in such a way that they form a hollow cylinder, withone pole of each magnet facing toward the centre of the group. The rotor is therotating electrical component. It also consists of a group of electro-magnetsarranged around a cylinder, with the poles facing toward the stator poles. Therotor is located inside the stator and is mounted on the AC motor’s shaft.” (ACMotor Diagrams-Basic Stator and Rotor Operation 2017). Figure 16,Basic electrical components of an AC motor. (Unknown Author (2017) Basic electrical components of an AC Motor).
Foran induction motor to be able to work, there is a need to have different speedsbetween the rotor and stator fields, as demonstrated in figure 17. Figure 17,speed differences between rotor and stator fields (Rayner, Robert 2017). Inductor motors involve rotating magneticfields, which move the machinery. Figure 18 shows the different components ofthe inductor motor: 1. Wires- they are conductors that carryelectrical current to sets of cooper coils which are called windings. 2. Windings- they are wrapped around steel barsand are energised windings from an electromagnet, which is called a stator.
3. Stator- the fluctuation polarity creates arotating magnetic field in the stator. This field crosses a 0.3 mm gap toinduce current in the lamination of the rotor, which spins around thestationary stator. 4. Rotor- The rotor faces a certain angle; thestator faces the rotor. The distance between the two, and the geometry of slotscarved into each set of laminations create two out of phase magnetic fields.The rotor spins as it repels the rotating magnetic field induced by the stator.
5. Housing- the illustration in figure 10 showsthe inside of a motor. It is shown that the fan blades attach to the bottom ofthe housing.
The vents on top cool the motor, as it needs breeze in order to doso. Figure 18,Single phase inductor motor of a ceiling fan (Sawyers, Harry 2011). Electrical characteristics are provided infigure 19 and 20.
Figure 19,Electrical characteristics part 1 (Rayner,Robert 2017). Figure 20,Electrical characterises part 2 (Rayner,Robert 2017). 2.
3 Ceiling fan energy and characteristics Single-phase inductors are simple and reliablemotors that can produce energy up to the unit of 1 KW. The torque characteristicsof a single-phase inductor are similar to the 3 phases. The difference is inthe starting torque because there isn’t any starting torque and capacitivesplit phase starting method is applied in this case. At the starting point, asingle-phase supply is divided into two phases at almost 90 degrees out ofphase with each other to be able to get a rotating flux. In the following 21-23, the characteristics ofan induction motor are shown. Figure 21,Induction motor characteristic (Rayner, Robert 2017). Figure 22,Induction motor characteristic example, part 1 (Rayner, Robert 2017). Figure 23,Induction motor characteristic example, part 2 (Rayner, Robert 2017).
Different ceiling fans have different poweroutputs. Fans from the size range of 36 inches to 56 inches use 55 to 100watts. Figures 24 and 25 show the global electricityprice ranges.
Figure 24,Global electricity prices part 1. (Unknown Author (2017) Global ElectricityPrices). Figure 25,Global electricity prices part 2 (Unknown Author (2017) Global ElectricityPrices). In figure 26, the energy used for a 48-inchceiling fan has been calculated, considering that it is being uses for 5 hoursa day at 75 Watts, at the United Kingdom rate of 25 kWh. Figure 26,Electricity usage of a ceiling fan. (Unknown Author (2017) Electricity usage of aceiling fan. The FanRPM low-speed fans have speeds of around 40 to 70 rpm per minute; themedium speed range is from 100 to 115, whereas high speeds hit 180 to 200. For the single phase start capacitive runinduction motor, it is developed from a low torque operation which has a rangeof 0.
22 to 0.72N-m, depending on the size of the blade. In Figure 27, thecomparison between different single-phase motors is shown.
Figure 27, Type of motor load. (Erlmarli,Khiri and others 2017). In the following figures 28 and 29, the motortorque output is provided. Figure 28,Motor torque output part 1 (Rayner, Robert 2017). Figure 29,Motor torque output part 2 (Rayner, Robert 2017). 2.
4 Ceiling fan efficiency The stator of a single-phase induction motor haslaminated stamping, to be able to reduce current losses on its periphery. Whenthe stator is given a single-phase AC supply, the magnetic field is produced. Themotor will then be rotated at a speed slightly less than the synchronous speedof Ns which is given by: In this equation f = supply voltage frequency,P= number of poles of the motor.
The single-phase induction motor is very widelyused in home applications as well as industrial, despite the fact that it has alower power rating because of the larger quantity and the fact that part of thetotal motor electricity consumption goes to this type of motors. Therefore, efficiencyin this motor is usually low. One method for the improvement of efficiency isthe well-known stator voltage control. Although it has very limited savingcapabilities in a limited speed range, it doesn’t have the potential of avariable frequency supply.
According to the research carried out by BijanZahedi the Maximum Efficiency conditions are shown in figures 30 to 33. Figure 30, Maximumefficiency condition part 1 (Zahedi, Bijan 2009). Figure 31,Maximum efficiency condition part 2 (Zahedi, Bijan 2009). Figure 32,Maximum efficiency condition part 3 (Zahedi, Bijan 2009). Figure 33,Maximum efficiency condition part 4 (Zahedi, Bijan 2009). From these equations given in the figures 31-33,it is clear that there’s a possibility to achieve the maximum efficiency, followingthe conditions.
However, the consequence of this is that this procedure iscostly. Figure 34 shows that single-phase motors areless efficient than three-phase induction motors. A three-phase motor has anefficiency of about 74 %. On the other hand, the single-phase motor has theefficiency of about 64 %.
The figure below shows that the full load of theefficiency of the single-phase motor is 64.66 %. Figure 34, Single phase data (Perez,Marc 2012). The best way to achieve maximum efficiency is byusing the windings current phase as an appropriate electrical control variable.Through this implementation, there is no need for any mechanical sensor. Themotor slip is controlled by controlling the windings current phase difference.A VSD with the ability of speed control and efficiency maximising in differentoperating points can be designed. According to experimental designs, it showsthat it is superior over the constant V/f control method and shows that it hashad an efficiency improvement of over 18 %.
3. ConclusionAll in all, ceiling fans are significantlycheaper than air conditioners, and they help save money and energy. In additionto that, they also generate warmth as well as cool air. Fan manufacturersestimate that consumers can save as much as 40% on bills during the season of summer.Although there’s a variety of ceiling fan models, the cheaper models tend to bethe noisiest, and tend to overheat quicker. However, they are still a popularchoice, as they are used by numerous people.
It is a one-time instalment, whichcan also be used as a decoration in the room. Although single phase inductionmotors are not the most efficient, they are economically friendly and don’ttake up too much power in houses, offices and industries and can function bysingle power system. They are reliable, easy to repair and maintain.