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. pdf from CSE 302 at World University of Bangladesh. is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. It is defined as the angular distance between the central line of one pole to the central line of the next pole. c. Expert Solution. An alternator having 10-poles, 3-phase, and 60 Hz has 8 conductors per slot in single layer arrangement with 4 slots/pole/phase. Because a chording more than 1/3 pole pitch would noticeably reduce the phase emf. 85 lagging. Note. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. three factors: the pitch factor (also called chording or coil-span factor), the distribution factor (also called breadth, spread or zone factor) and the skew factor. The total flux per pole is 10⁶ lines. m. b. The current is in same direction in both the sides of the coil. A 3-phase, 50 Hz, 2-pole, star connected turbo alternator has 54 slots with 4 conductor per slot. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. It is always 180° electrical. Hence, during rotation when one side of the coil comes under north pole, the other side of the coil comes under south pole. When a coil is having a span of 180° electrical, it is called a full-pitch coil. Coilspan or coil-pitch. Hence emf induced in one side of. 0 B. 6. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. In other words, the distance between the two coil sides of a coil will be equal to the distance. It is sometimes convenient to speak of an armature coil span as having a fractional pitch expressed as a fraction e. • To view the coil sides / coils, we must look below from above the slots as depicted in figure. Kr ==sink 2 · Kp =pitch factor in dcci111al p" =span of the coil in electrical degrees. This problem has been solved! You'll get a detailed solution from a subject matter expert that helps you learn core concepts. Calculate the armature winding distribution factor. Pole pitch is always equal to 180o. To get a coil around every tooth, we need two winding layers (double layer winding). Machine, Nagpur Univ. A winding constituting a basic unit under a pole-pair (N and S) is repeated for any number of pole pairs when q is integral. #Alternator #Protectionofalternator#elect. Commutator pitch of a progressive lap winding is yc = +1. The maximum pole flux is 8. With a full-pitch coil, the emfs induced in the two coil sides are. 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 ____________. . p. BUY. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. As shown in Fig. The coil pitch is short by 2 slots. Transcribed Image Text: (d) obtain a full-pitch winding. , the case of short-pitch coil, the voltages generated in each coil side are not in phase. 5. It may be the full pitched or short pitch. Calculate the rms value of the induced emf per phase of a 10-pole, 3-φ, 50-Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. Pole – pitch. 6. A coil is said to be fully pitched when the coil span is made equal to the pole pitch of the machine. The alternator has 18 slots per pole and the first coil lies in slots 1 and 16. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. A. 0 i D. 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. (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. 85. However in practise this often isn’t the best choise because of the high harmonic content. ); and k y is the short pitch factor. ed = electrical degree Example 2: Calculate the pole pitch for a three phase 4 pole ac machine having 36 stator slots. However, the phase winding factor for short-pitched coils is different from that of full-pitch coils. In this case, we have a 10 pole alternator with coils wound in a fractional pitch of 18/21. The pitch factor, in rotating electrical machinery, is. A 3 phase 1800 kVA, 3 kV, 50 Hz, 250 rpm, salient pole. Pole – pitch. The value of α will usually be given in the question, if not, then assume kc = 1. 0. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. 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. advertisement. 5. K pn = cos nα/2. Assume that the coil span is 150° electrical. For alternator having fractional pitch winding of 8/14 the coil span is 102. Coil Span: It is the angular distance between the two sides of the coil. 966the coil span of the two slot‐pitch technique has been pro-posed, based on the ‘stator shifting’ concept [8, 9]. e. 8 slots b. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . Now coil is shorted by 1 slot i. 🔥engineers platform App Link. This advancement is measured in terms of armature conductors and is called back pitch. The primary reason for making the coil span of a d. 2. 24, and assume first a short-pitched coil spanning half a pole pitch, then a long-pitched coil spanning one and a half. The pole pitch is 35cm, the core length is 32cm & sta- 4th tor coil span is of pole pitch. o5Wb. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. 26. The average pitch Y A = 2 B F Y Y +. Back Pitch. in the two sides of the coil. 00 O…influence of slot/pole number (S/P) combinations on the rotor bar copper loss, a winding harmonic index is described in Section 2. Pole pitch is the electrical angle between the north pole and. It means that coil span is 180 electrical degrees. Define Pitch Factor /Distribution Factor and present the formula to calculate. Coil–span or coil-pitch. pole pitch = 180 electrical degrees or π electrical radians. Solution : n = Slots/pole = 36/4 = 9. 0. kp: 0. , angle between the two sides of. armature winding equal to a pole pitch is to (a) obtain a coil span of 180° (electrical) (b) ensure the addition of e. Coil span is simply a peripheral distance between two sides of a coil. In this. ISBN: 9780073373843. 1, if the coil sides are placed in slots 1 and 7, then it is full-pitched. There are 2 coil sides per slot. Share on Whatsapp Latest UPSC IES Updates. , coil span is 180º electrical) is called a full-pitch coil. Number of empty slots = 18 – 15 = 3 slots ( herefore alpha = 180^circ imes frac{3}{{18}} = 30^circ). The armature winding is housed in 360 stors with 6 conductors per slot. (Elect. Assume the coil span as 150° electrical. Commutator pitch Y C = ±1. 4. 6. If the high speed coil span was 1/2 of pole pitch, then there would be roughly equal airgap circumference for induced poles as exists for the driven poles in slow speed, and no need for homopolar flux in the shaft. fs. 150° is (frac{5}{6}) parts of 180° i. Calculation:A coil rotated in a magnetic field induces current. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. Determine the equation for the. 14. Discuss the effect of making the coil span very different from the pole pitch on (a) the coil emf and (b) the coil torque. Generators 897 winding is fractional-pitched. The coil span is 150 electrical degrees. The flux distribution curve of a smooth - core 50 c/s generator is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. The theoretical coil pitch yp (or span) is the number of slot pitches between the two coil-sides of the same coil. arrow_forward. ∴ e = E 1 + E 2 = 2E. Coil Span: It is the angular distance between the two sides of the coil. 3 percent. The pole pitch is 35 cm. You can compare the maximum fundamental winding factor for different combinations of number of poles and number of slots, display the winding layout for different coil spans,. Fig. Transcribed Image Text: (d) obtain a full-pitch winding. In practice, coil pitch (or Span) as low as eight-tenths of a Pole Pitch, is employed without much serious reduction in emf. In an alternator, for a coil having a span of 2/3 of pole pitch,. 7. It is usually measured in terms of teeth, slots or electrical degrees. 1K 39K views 2 years ago AC Electrical Machines Jimit Tutorials In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch,. 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. Study with Quizlet and memorize flashcards containing terms like A lap winding, Twice, Full-pitch and more. When the parallel path is twice the number of poles then it is known as Duplex Lap Winding. . To improve the wave form only 80% of the pole pitch is wound. Full pitched coils have the advantage of giving maximum emf induced in the coil. AC compound generator usually has lower resistance. In a 4-pole, 35 slot dc armature, 180 electrical degree coil span will be obtained when coils occupy _____ slots. The harmonic reduction in the voltage waveform of concentrated winding axial field PM machines is the subject of interest for many researchers. As against this if coils are used in such a way that coil span is slightly less than a pole pitch i. The resultant coil voltage $𝐸_{𝐶}$ is equal to the phasor sum of $𝐸_{𝐶1}$ and $𝐸_{𝐶2}$. , pole-pitch ) is known as 'Full Pitch'. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. Publisher: McGraw-Hill Education. Coil span or Coil Pitch. There are 4conductors per slot and a sinusoidally distributed flux per pole of 36mWb. For example, the below image shows the 2p6s machine with double layer winding with the coil span being 2 slots (120 degree electrical) instead of 3 slots (180. Display and compare winding harmonicsElectrical Engineering. Distribution factor (K d): The ratio of induced emf in the coil group when the winding is distributed in number of. Calculate the coil span factor or the pitch factor for the following windings: ( a) 54 stator slots, six-poles, when coil spans 1 to 8. the flux per. Required: a. On the other hand, if its span is less than a pole-pitch. Also note that the diagram gives no information about the coil-span or pitch; thus for example in the 36-slot case a full-pitch winding would have a coil-span of 9, but 8, 7 or 6 could also be used (all with 2 coil-sides per slot). In a 4 pole, 54 slot dc armature, calculate the coil span. 4, Fig. 10 A three-phase, wye-connected alternator has 15 slots/pole. Electrical Engineering. α = Angle of short pitch = 20o. Here, e = E 1 = E 2 = E. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. 2 Selecting the coil span for a given pole pitch. How many comparators does a 339 IC contains? 4. arrow_forward. A pole pitch in an electrical machine is equal to 180° electrical. Coil span Coil span (also known as coil pitch) is the angular distance between two sides of a coil, measured in terms of armature slots. I need answer within 20 minutes please please with my best wishes. The pole pitch is defined as the distance between two consecutive poles. The winding is wye-connected. However, the coil span may be less than a pole pitch, in which case the coil is described as short pitched or chorded. 707 B. 31. The pitch factor corresponds to the mean span of the coils of the winding with respect to the pole pitch while the distribution factor quantifies the flux reduction due do the winding distribution inside a finite number of slots. Ensure the addition of e. Theta (electrical)=p/2 (theta (mechanical)) What is the formula for electrical angle. If the angular distances between the two coil sides are less than one pole pitch, it is termed short pitch or fractional pitch coil. 1. Assume = 0. If the coil sides are placed in slots 1 and 6, then it is short-pitched or fractional-pitched because coil span is equal to 5/6 of a pole-pitch. ) Given: 120 slots, ,10 poles, double layer winding, coil pitch is shorted by 2 slots, f=60 Hz, Y connected. Place the arrows according to the slot pitch. What is the coil span for a 4 pole 48 slot machine? Explanation: Slots per pole = 48/4=12, for a coil span of 10 slots, the coil is short pitched by 2 slots and the chording angle is ε=2γ and γ=180/12 ⇒ ε = 30° ⇒ Kp=cosε/2=0. Understand what Full Pitch and Short Pitch Windings are, and what Coil Span is. Determine the equation for the emf induced in one turn, and its RMS value. The coils are made up of 8 turns, and the windings are double layer. 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 phase spread is 60° and the flux per pole is 25-8 x 10 weber. Thus the total emf at the coil terminal A & B is the phasor sum of (E 1 +E 10), (E. F. The. Draw the double layer winding layout for a 24 slot stator and 4 pole alternator 3. The pole pitch is 35 cm. Thus coil span of either 6 or 7 may be selected. A=2, B=1 and C=2 and D=5. It is always less than unity. 2. Answer: a. 05: B) 0. m. c. ’s of consecutive turns c. Concept: Coil pitch or coil span: It is defined as the angular distance between the two coil sides of one coil. Pole pitch is always equal to 180o electrical. The two sides of a coil are places in two slots on stator surface. Calculate the pitch and distribution factors for the fundamental, the third, and the fifth harmonics in the phase voltage. Electrical Engineering questions and answers. Pole pitch is the mechanical angle between adjacent poles, e. The separation between the top and bottom sides of a coil is called Coil span. The winding pitch of a generator is the number of slots spanned by each coil in the stator winding divided by the number of slots per pole. Boylestad. Note. A 3-phase, 4 pole, Y- connected alternator has 72 slots with two conductors per slot. A coil whose sides are separated by one pole pitch (i. 15 Consider the armature conductor marked X in Fig 1. g. SEE MORE TEXTBOOKS. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. Problem. e. electrical degrees indicate the amount the currents in conductors has changed. Pole pitch = 180 electrical degrees = S/P = 2C/P. Answer: c Explanation: Pole pitch is called as center to center distance between two adjacent poles. If the coil span is. e. An 8-pole lap wound DC generator has 120 slots having 4 conductors per slot. (2) 𝑘 𝑐 𝑛 = c o s 𝑛 α 2. The coil span is 150 electrical degrees. ; It means one side of the coil in a particular slot, after how many conjugative slots, the other side of the same coil is placed. * This angle is known as chording angle and the winding employing short-pitched coils is called chorded winding. Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. 0. 11. M. It is one pole pitch. 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 . Q2: 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 3 rd harmonics. The flux per pole has a fundamental component of 0. See solution. Also note that the diagram gives no information about the coil-span or pitch; thus for example in the 36-slot case a full-pitch winding would have a coil-span of 9, but 8, 7 or 6 could also be used (all with 2 coil-sides per slot). Solution for For alternator having fractional pitch winding of 10/14 the coil span is 4. Hence, the pitch factor or the coil span factor for the n th harmonic is given by, kcn = cos nα 2. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. In a short pitch coil, the coil span will be (180 -. m. The coil-span chosen is less than the full-pitch because of the inherent advantages of chording. Pole pitch. B. Download these Free Coil Span or Coil Pitch MCQ Quiz Pdf and prepare for your upcoming exams Like Banking, SSC, Railway, UPSC, State PSC. 150 degree (electrical). the coil will be in 180o. Resultant flux in the air gap is 55 mWb per pole. A 4-pole, 3-phase synchronous machine has 48 slots. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. For example, in a 6-pole armature having 96 slots, a coil spanning 15 teeth would obviously be a fractional-pitch or chorded coil (since pole-pitch is 16). Answer: 0. Pole Pitch, Coil Span, Back Pitch, Front Pitch, Commutator Pitch in Armature Winding of DC Machines are explained in this video. For A. 9659When the coil span is lower than pole pitch, the phasor sum of conductor voltages is less than the arithmetic sum, because of vector addition. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2. it is defined as the peripheral distance between the center of two adjacent poles in a DC machine. If t he coil pitch is y =3, the diame tral w inding w ill have the f. 16 wb/pole and is distributed sinusoidally over the pole. , 5 slot‐pitches in Figure 2a) [8, 9]. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. 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. For a 3-phase winding with 6 slots per pole per phase and with coil span of 15 slot, the value of pitch factor is A. 71 O 120. P˚ = Pitch = coil span in no. Emf induced per coil side is E. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. The term "region" is important, because a design with 3 slots per pole and phase, for instance, can only be pitched 6/9 or 7/9 or 8/9. On the other hand, if its span is less than a pole-pitch. 1: How to get flux, based on the rotor, through a coilspan coil (the coil span is closest to pole pitch, 3. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. . The four coils of Phase A would span between slots 1 and 6, slots 2 and 7, slots 7 and 12 and slots 8 and 1. 951, 0. Question. 79. You can compare the maximum fundamental winding factor for different. to the induced emf in the same coil when it is full pitched is called a coil span factor or pitch factor or chorded factor and it is generally denoted be K p. by 20o to full pitch distance. Find the EMF produced by a DC generator connected to a 6 poles coil rotating at 1200 RPM. Pitch factor. 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 0. So if coil side in slot No. The separation between the top and bottom sides of a coil is called Coil span. 5 are the stator low-order voltage harmonics for the different motors with 120°, 140°, 160° and 180° coil pitch at half load, full load and overload, respectively. Distribute the winding uniformly under different poles d. Learn what a pole pitch is, the pole pitch formula & definition, and how to. Obtain a coil span of 180 degrees (electrical) b. none of the aboveThe coil span generally varies from 2/3 pole pitch to full pole pitch. Electricity for Refrigeration, Heating, and Air Conditioning (MindTap Course List). 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). A chording angle ε is defined as the angle by which coil span departs from _____ a) 90° electrical space degrees b) 180° electrical space degrees c) 360° electrical space degreesSolution: No. Here, the 1This means, if E 1 and E 10 are the emf induced in respective coil sides then the total emf induced will be E 1 +E 10. 455 V D. We will start Red at slot 1. In general, if the coil span falls short of full-pitch by an angle α (electrical)*, then kc = cos α/2. e. In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch, back pitch, pole pitch, coil pitch, etc. P. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. of slots/pole/phase, m = 4 ma 2x30 ata Soest 0-9659 (Ans. Pitch Factor·· the ratio of the voltage generated in ti1e fractional-pitch coil to the voltage generated in the full-pitch. arrow_forward A. per slots, in a double layer. 33 percent of pole pitch to obtain the maximum reduction of harmonics. It is equal to the number difference of the conductor connected to a given segment of the commutator. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. The coil used in double layer winding are diamond shaped as in the dc windings. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. Calculate the RMS value of the induced emf per phase. Understand what Full Pitch and Short Pitch Windings are, and what Coil Span is. Explain the following armature winding terminologies (i)commutator Pitch (ii)Coil Side (iii)Pole Pitch. 363Wb and a 15% third harmonic. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. The fundamental pitch. If each coil spans 8 slot pitches, what is the value…Front pitch: The distance between the last side of the first coil and first side of the second coil is called the front pitch. 26. A 10 MVA, I KV, 50 Hz, 3-phase, star-connected synchronous seberatur is driven ur 300 r. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. If the coil span is exactly equal to the pole-pitch, then such a coil is called a full-pitch coil. If the coil sides are placed in slots 1 and 6, then it is short-pitched or fractional-pitched because coil span is equal to 5/. 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. On the other hand, if its span is less than a pole-pitch. In this video lecture you will learn about electrical angle,mechani. The two sides of a coil are placed in two slots on the stator surface. The armature has double layers winding. Where n is the nth harmonic. 8. Share on Whatsapp India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses. • So coil span is 16/4 = 4. 125 Wb and a. situation, two opposite sides of the coil lie under two opposite poles. When measured in electrical degrees one pole itch is equal to 1800. Key. The arc diagram contains all the necessary information for connecting the pole-groups correctly. For n th harmonic. (2006), “Distribution, coil-span and winding factors for PM. When 40V DC voltage is applied to a single-phase AC motor, it draws 1A current. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. 7. is known as coil span. 9 and the efficiency is 0. Its value is always less than unity. , coil span is 180º electrical) is called a full-pitch coil. The electrical space angle between the active coil length or coil side is equal to one pole pitch. Note that although the span of a full-pitch coil is not an integer in a fractional-slot winding, the full-pitch coil is nevertheless an im- The correct answer is option 3. Figure 4 shows the flux distribution linked to a short-pitch coil. Calculation:The angular distance between the two coil sides is less than one pole pitch, it is termed short pitch or fractional pitch coil. The pitch of the coil has 4 slots less than the pole pitch. Coil-span or Coil pitch (Y s) It is the distance, measured in terms of armature slots (or armature conductors) between two sides of a coil. Coil Span Factor - Coil Span Factor is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them. where: 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. The coil pitch is equivalent to the span, except that this term is used more often in a theoretical context and expressed in electrical degrees, or per-unit of a pole-pitch. There are B coil groups of (A+1) coils, that is, 1 coilIf the pole span or coil pitch is equal to the pole pitch (as in the case of coil A in Fig. ’s of consecutive turns c. Determine the equation for the emf induced in one turn, and its RMS value. 866. c. BUY. PITCH FACTOR OR COIL SPAN FACTOR Pitch Factor – the ratio of the voltage generated in the fractional pitch coil to the voltage generated in the full pitch coil. The pole pitch is 35 cm, the core length 32 cm, and the stator coil span coil span four fifth of the pole pitch. Calculate the pitch factor of the coil for 3 rd harmonic.