e. 4 pole = 90º. Design a suitable double-layer lap winding for a 6-pole armature with 18 slots and two coil-sides per slot. In a fractional pitch winding, the coil span is made less than 180 degrees electrical space. The dc armature winding in which coil sides are a pole pitch apart is called ____ winding – Full- pitch. 12 3-0. In other words, the distance between the two coil sides of a coil will be equal to the distance. Author: Robert L. 2 sin 50 +0. Each of these coil spans is five slots, so this choice of winding. The current is in same direction in both the sides of the coil. In a 4 pole, 3 phase alternator, armature has 36 slots. 0. The coil pitch is 5/6th of the full pitch and the flux per pole is o. Generally. For A. Degree of Reentrancy c. 163Wb. Coil–span or coil. . It may be the full pitched or short pitch. Normally the nearest whole number is selected which is 6 in present case. The armature windings conduct AC even on DC machines, due to the commutator action (which. Zoom In Zoom Out Reset image size. Front pitch (Y f):. Despite its disadvantages, it is common in mass production. 4. It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. The flux per pole is 80 m Wb and the coil span is 160° electrical. The stator of a synchronous machine is such that:3-phase; 4 poles; 36 slots; winding double-layered; 2 slots short pitched and 2-turn for each single coil. It is usually measured in terms of teeth, slots or electrical degrees. it is said to the a fractional-pitch. If the coil span is less than the pole pitch (as in coil Fig. There are 2 coil sides per slot. 57. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. Ratio of the pole arc to pole pitch: 0. 1993) Example 37. . As shown in Fig. in them are additive. 15 Consider the armature conductor marked X in Fig 1. coils having span which is equal to one pole-pitch i. 26. Its flux per pole is 0. What is the coil span for a 2 pole 18 slot machine? a) 9 b) 4. If the coil span is equal to the Pole pitch then it is called a full pitch coil. 2. in the two sides of the coil. Let us assume that, a coil is short pitched by an angle α (electrical degree). A 4-pole, 50 Hz alternator has double layer winding with 10 turns per coil and number of slots are 60. First. Here, e = E 1 = E 2 = E. The coil-span chosen is less than the full-pitch because of the inherent advantages of chording. (8) A SIMPLE explanation of Full Pitch and Short Pitch Winding. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. N st 2p r; 12 14 16 18 20 22; 12:. fs. e. TYPES OF AC MACHINES WINDINGS. 955, whilst the second option gives (k_{sk1}) equal to 0. 0 C. It mainly focuses on two PM machines with different slot/pole number combinations (N s /2p), that is, the 24-slot/10-pole and 24-slot/14-pole machines (2p = N s /2 ± 2). 1. 4. Use a diagram like that shown in fig. the coil will be in 180o. A 3-phase, 8-pole, 60-Hz, star-connected alternator has 96 slots with 10 turns per coil. 36K subscribers Subscribe 9. 24 B where coil pitch is 3/4th of the pole pitch), then the D. D. A pole pitch is always 180 electrical degrees, regardless of the number of poles on the machine. Calculation: Given that, Number of coils = 16Q2: For a 3-phase winding with 3 slots per pole per phase and coil span of 8 slots, compute the distribution and pitch factor for fundamental and 3rd harmonics. The pitch of the coil has 4 slots less than the pole pitch. This winding has 12 slots per pole per phase. placed in the top layer of the slot & the other side of the coil is placed in the bottom layer of another slot nearly a pole pitch apart. 75), the lowest 2-solt coil span. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. 1 is connected to coil side in slot No. m. In this case, the coil sides lie under opposite poles, hence the induced e. If the coil span is equal to the Pole pitch then it is called a full pitch coil. To get a coil around every tooth, we need two winding layers (double layer winding). Solution for For alternator having fractional pitch of 11/12 the coil span is a. If the coil. number of slots and a coil span of two slots require at least 18 slots. Note. The coil span should be minimum of about 8. 951: C) 0. The windings are arranged as 5 conductors per layer. it is defined as the peripheral distance between the center of two adjacent poles in a DC machine. The separation between the top and bottom sides of a coil is called Coil span. In this. 7. There is a formula for calculating electromagnetic torque based on magnetic flux, distribution factor, and pitch factor [18] as equation 8. Comparator. 1NP2. Better emf waveform in case of generators 6. Short-pitch windings have a coil pitch of less than 1, which means the coil span is shorter than. BUY. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. A coil whose sides are separated by one pole pitch (i. The pole pitch is defined as the distance between two consecutive poles. a coil. Hence emf induced in one side of the coil will be in 180° phase shift with emf induced in the other side of the coil. The pitch of the coils is 2 slots less than the pole pitch. It is expressed in terms of number of slots per pole. For a short pitch coil KC. The pitch factor for third harmonic in an alternator having 18 slots per pole and coil span 5/6 of pole pitch is _. m. Download Solution PDF. Determine the pitch (or coil span) factors for the winding ,24 Stator slots ,4 poles, coil span 1 to 5 12. Here, e = E 1 = E 2 = E. In this paper, the influence of changing the span of the concentrated coil for a certain pole pitch on the harmonic content in the output voltage. ∴ e = E 1 + E 2 = 2E. Wheres is the number of slots, and 2p is the number of poles [19]. F induced in one side of the coil will be in 180˚ phase shift with E. . because of that the pole pitch is 9/4 of the slot pitch, thus the three-phase symmetric distributed windings consist of 18 double-layer coils that can be used, in which each coil span. View 26 DC Generator. In a 10 pole, lap wound de armature, the number of active armature conductor per pole is 50. what is coil pitch or coil span. Figure 8 compares computed waveforms of phase back emf. Q: Explain the following Armature Winding Terminologies (i) Coil Span (ii) Resultant Pitch A: In the following section, coil span and resultant pitch related to armature winding technology has… Q: Assume that a four-pole de machine has an armature with a radius of 15 cm and an effective length of…In the second example, with a pole pitch of 15. The reduction fraction is the pitch factor. What is meant by a full pitch winding a fractional pitch winding? If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. It may be the full pitched or short pitch. (BTL-1) 4. Discuss the effect of making the coil span very different from the pole pitch on (a) the coil emf and (b) the coil torque. A full-pitch coil is one whose pitch is equal to the pole-pitch at the working harmonic. 339 IC function as. For n th harmonic. the coil will be in 180o. For example, in a 4-pole generator with a 48-slot stator (12 slots per pole), if each coil in the stator winding spans 12 slots then the ratio is 1/1 and the winding is full pitch. Calculate the emf generated in each phase when the machine runs at 375 rpm Hence, pitch factor or coil span factor K p = Cos(/2). If the coil span is exactly equal to the pole-pitch, then such a coil is called a full-pitch coil. It is also called a chorded coil. The pole pitch is always 180 degrees electrical regardless of the number of poles in a machine. Figure 4 shows the flux distribution linked to a short-pitch coil. kp: 0. Based on the prototype of the long stator LSM we designed, the effect of different short-pitch factors on the propulsive force was studied: (8) {y p θ = τ π k y = sin θ 2 where y p is the short pitch, denoted by length; θ is the short pitch angle (rad. To get a coil around every tooth, we need two winding layers (double layer winding). 1 times the pole arc. Calculate the sinusoidally distributed flux per pole required to give a line voltage of 11 kV on open circuit, and the full load current per conductor. Therefore one coil, such as coil 1 which traverses slot 1 and 7 falls under the north and south pole exactly because they are 180º apart as seen in the image above. 15, 13; 19, 17; 21, 19; 23, 21;150° is (frac{5}{6}) parts of 180° i. C. For a coil span of 13/15 of a pole pitch, the phase winding factor is: K_p = cos(π * 13 / (2 * 15)) = 0. fs. All coils in a phase are connected in series. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° =. (b) Determine the pitch (or coil span) factors for the following windings: i. e. The pole arc should be about 70% of pole pitch and length of core about 1. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. The armature coils are all connected in series. Problem 1 : Develop the layout of a lap winding for a 3 phase ac machine having 4 pole and 24 slots. This advancement is measured in terms of armature conductors and is called back pitch. 6. The armature has double layers winding. EE - 422 DC & AC MACHINERY 2nd Semester AY 2020-2021 ENGR. The pitch factor, in rotating electrical machinery, is defined as the ratio of resultant EMF of a _____ a) full-pitched coil to that of a chorded coil b) full-pitched coil to the phase EMF c) chorded coil to the phase EMF d) chorded coil to that of a full-pitched coil View AnswerCalculate the pitch factor for an alternator winding with 36 slots, 4 poles, and coil span of 1 to 8. 1. Pole pitch is the peripheral distance between two adjacent poles. slots. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. What are the different types of stator windings in induction motor? Ø. Note. fs. . Hence, during rotation when one side of the coil comes under north pole, the other side of the coil comes under south pole. Participate Now!Since 1 pole pitch is the angular distance between the two consecutive poles which is equal to 180 electrical degree, therefore the coil span for full pitch coil is also equal to 180 electrical degree. 135 degrees d. With a full-pitch coil, the emfs induced in the two coil sides are. The theoretical coil pitch yp (or span) is the number of slot pitches between the two coil-sides of the same coil. Download Solution PDF. A 4-pole, 50-Hz, star-connected alternator has 15 slots per pole and each slot has 10 conductors. Concept: Coil pitch or coil span: It is defined as the angular distance between the two coil sides of one coil. It is lesser than the value in the first case. Calculared the flux per pole required to give Il kV line voltage on open circuit voltage. The arithmetic sum of induced emfs is 2E. phase shift with emf induced in the other side of the coil. advertisement. 24, and assume first a short-pitched coil spanning half a pole pitch, then a long-pitched coil spanning one and a half. 60o / 90o = 2/3. ’s of consecutive turns c. If the coil. Armature Currents and MMF of 5-Phase Machine The armature currents of 5-phase machine can be expressed with formula (1). ∴ e = E 1 + E 2 = 2E. Both Y B and Y F should be nearly equal to a pole pitch. B. Then, the pitch factor will be equal. Pole Pitch: It is the angular distance between the two adjacent poles. The commutation is. Compared to the overlapping winding above we need only 3 slots for the two poles. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. See solution. 772 x 10-3 Wb. The harmonic reduction in the voltage waveform of concentrated winding axial field PM machines is the subject of interest for many researchers. The value of α will usually be given in the question, if not, then assume kc = 1. per slots, in a double layer. In SWAT-EM we can set the coil span explicite. The slots per pole per phase are 8 and the coil span is 20 slots. 951, 0. , angle between the two sides of. 6. Commutator pitch Y C = ±1. e. 05 Wb, sinusoidally distributed. o5Wb. The coil span is 150°. 1, or nonsalient (flush with the surface of the rotor), as shown in Fig. Fig. 125 Wb and a. a. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. . 866. 12. Its value may be calculated by the equation kp=sin p°/ Where kp =pitch factor (always decimal for fractional-pitch winding) p° = span of coil in electrical degrees ( coil span/slot/pole x180°) Example: Calculate the. The induced emf in each coil side. A. Transcribed Image Text: (d) obtain a full-pitch winding. Question. Example: the throw could be to 9 meaning that one side of the coil is. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. Alternatively, this type of coil is also called a short-pitch or chorded coil. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. The distance between the two sides of a coil is called the coil. ( ) () ⎪ ⎪ ⎪ ⎩ ⎪⎪ ⎪ ⎨ ⎧ = − = − = − = − = sin 8 /5 sin 6 /5 sin. The coil span is 150°. Both, 7/9 and 8/9, are equally close to 5/6 but I would select 8/9 for better flux utilization. Find equation of 5 EMF induced in one turn and its RMS valueIn this study, the electromagnetic performances of dual 3-phase permanent magnet (PM) machines with coil span of two slot-pitches are comparatively investigated. 0. Three kinds of coil spans are used, they are 4-solt pitch, 3-solt pitch, and 2-solt pitch. g. 125 Wb and a. It is lesser than the value in the first case. Not ( I want a solution within 20 minutes because it is very urgent ) Q3//The armature of a 6600 volt, three-phase, 20-pole, 300 rpm star-connected alternator has 180 slots. 33 percent of pole pitch to obtain the maximum reduction of harmonics. Back. P˚ Kp = sin [(90°)(pitch)] Kp = sin 𝟐 PROBLEM 1: A 6 pole, 3Φ AC generated has 72 slots, the coil span is 12. At this situation, two opposite sides of the coil lie under two opposite poles. For a three-phase winding with 6 slots per pole per phase and with a coil span of 15 slots, the value of pitch factor is This problem has been solved! You'll get a detailed solution from a subject matter expert that helps you learn core concepts. 31. y=Coil span τ=Z/2P is the Pole pitch or full span II. The width of the coils is 5/6 of the pole pitch. 165 degrees. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. In all cases, the coil span should not differ too much from the pole pitch to ensure that when one coil side is under a north pole, the other coil side is under a south pole . (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. Pole Pitch, Coil Span, Back Pitch, Front Pitch, Commutator Pitch in Armature Winding of DC Machines are explained in this video. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. The highest winding factor can be obtained with 4-solt span coil (the coil span is closest to pole pitch 3. Find the terminal voltageon open circuit. 3. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. . Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. e. For making coil span equal to a pole pitch in the armature winding of a dc generator, the back pitch of the winding must equal the number of – Commutator bars per pole. Petruzella. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. The winding is wye-connected. 15. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. 0. This is shown in the figure to left. A Three-phase four-pole AC machine has 60 coils in the stator and each coil has 100 turns. Coil span factor (Kc): The ratio of emf induced in a short-pitched coil to emf induced in a full-pitched coil is called coil span factor or pitch factor or chorded factor. Let us assume that, a coil is short pitched by an angle α (electrical degree). by 20o to full pitch distance. o. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a full-pitch winding. ( b) 42 stator slots, four-poles, coil. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. ∴ Coil span factor, Where β is the angle through which the coil is short pitched. See moreIf the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. It is always less than unity. of poles, P= 4 No, of slots = 24; No. Coil Span Factor: In a full pitch winding the coil span or coil pitch is always equal to the pole pitch which is equal to 180 electrical degrees. We will start Red at slot 1. A 3 phase 1800 kVA, 3 kV, 50 Hz, 250 rpm, salient pole. 60o groups, 2-layer winding is used. A coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below. electrical-engineering Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the ____________. There. If the span of the coil is reduced by an angle 'α' of electrical, then the. If the coil-span (or coil-pitch) is equal to the pole-pitch, then the coil is termed a full-pitch coil. The meaning of FULL-PITCH WINDING is the winding of an armature in which the two sides of the armature coil span a distance equal to the pole pitch. 2 Selecting the coil span for a given pole pitch. This. We make the coil span less than 180 degrees electrical space degrees in a fractional pitch winding. 0. . . 85 lagging. Short pitch coil: If the angular distances between the two coil sides are less than one pole pitch, it is termed a short pitch or fractional pitch coil. Coil pitch: The distance measured in terms of armature slots or armature conductors between two sides of a coilQuiz # Solve the following problems. 2:. 1 times the pole arc. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. Every coil is connected to the commutator. MARASIGAN, REE, RME Figure 11 If the coil span is less than the pole pitch (as in coil B where the coil pitch is ¾ of the pole pitch) then the winding is fractional pitched. The coil span is 150 electrical degrees. Calculate the RMS value of the induced emf per phase. Pole pitch is always equal to 180o electrical. Q1/ Calculate the voltage per phase for a 3-phase 1500 rpm, 4-pole alternator having a 16 conductors per slot connected in two layers. If each coil is short pitched by an angle of 36 ∘ electrical. A coil when placed in a slot, the distance between two coil sides of a coil is equal to the distance between the center of one pole to the center of an adjacent pole ( i. It is using an armature winding which is short pitched by one slot. The formula for pitch factor is given by The pitch factor in the above equation is for fundamental component of emf. Transcribed image text: 1. Pitch: Pole and Winding • Pole pitch is the mechanical angle between adjacent poles, e. The fundamental flux per pole is 0. fs. Pole and slot numbers. winding is fractional-pitched. Here, e = E 1 = E 2 = E. Condition for designing a Mush winding:- 21. 10. The number of segments lying between the ends of the coil is known as the commutator pitch. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. the coils cannot be full - pitched; they may be short - pitched with 15 slots, or long - pitched with 16 slots. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. Last updated on Nov 23, 2023 UPSC IES Final Result 2023 Out on 22nd November 2023!If α be the angle in electrical degrees, by which the span of the coil is less than a pole pitch in the alternator, then mathematically pitch factor is defined as. A) 1. air. Calculate the RMS value of the induced emf per phase of a 10-pole, 3-phase, 60_Hz alternator with 3 slots per pole per phase and 4 conductors per slot in two layers. . If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. Expert Solution. none of the aboveThe coil span generally varies from 2/3 pole pitch to full pole pitch. arrow_forward. 2. . 80The coil pitch of such distributed windings is normally at least three slots which brings about a high winding resistance and occupies much space for the end windings. Not ( I want a solution within 20 minutes. Full pitched coils have the advantage of giving maximum emf induced in the coil. Winding table. Hence pole pitch is equal to total numbers of armature slots divided by total numbers of poles, we alternatively refer to it as armature slots per pole. Here, e = E 1 = E 2 = E. 3 mWb and the total number of armature conductors is 1000. Expert Solution. In this case, there is a phase difference between the e. In a short pitch coil, the coil span will be (180 – α)° electrical ( α = angle by which coils are short-pitched and always less than pole pitch ). 0 B. ∙ 10y ago. The slots per pole per phase are 8 and the coil span is 20 slots. If the coil span is equal to the Pole pitch then it is called a full pitch coil. Thus coil span of either 6 or 7 may be selected. 14. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2 coil sides per slot. is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. Hence E. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. . The analyses of different six-pole winding configurations, obtained by changing the coil pitch number, winding layer, and stator slot number for the families of , are presented in Section 3. 0:00 / 15:33 What is Coil Pitch and Pole Pitch /what is electrical and mechanical angle in Urdu/Hindi IK LECTURES 2. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. Identify the approximate diameter and length of stator core,.