Assume that the coil span is 150° electrical. There is a formula for calculating electromagnetic torque based on magnetic flux, distribution factor, and pitch factor [18] as equation 8. The arc diagram contains all the necessary information for connecting the pole-groups correctly. A 4 pole, 12 slot lap wound dc armature has two coil side per slot. When the coil span is less than 180 electrical degrees, the winding is called short pitched or fractional pitch or chorded winding as shown in Fig. Step by step Solved in 4. 12. Let us assume that, a coil is short pitched by an angle α (electrical degree). In an alternator, for a coil having a span of 2/3 of pole pitch,. Pitch factor or coil-span factor In general, if the coil span falls short of full-pitch by an angle (electrical)*, then kc = cosα/2. β = 180o/ = 20o. 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. 7. In a 4-pole, 35 slot d. Prob. 086 Wb, what will be the values of the emfs? phase. 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. 🔥engineers platform App Link. In this alternator one pole spans twelve slots. Calculate the emf generated in each phase when the machine runs at 375 rpm Hey Aspirants. 10 slots d. The Separation between the top and bottom sides of a coil is known as back pitch and is represented by (Y b). c. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. Copy. If each coil is short pitched by an angle of 36 ∘ electrical. The separation between the top and bottom sides of a coil is called Coil span. In this. The pitch factor of an alternator is a measure of the winding distribution along the armature. Pole arc/ pole pitch = core length/ pole pitch = 0. 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). When the parallel path is twice the number of poles then it is known as Duplex Lap Winding. It is usually measured in terms of teeth, slots or electrical degrees. For n th harmonic. 4. Chorded-coil. 6. 15. On the other hand, if its span is less than a pole-pitch. c. Pole and slot numbers. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. round the coil which is the vector sum of e. F induced in the other side of the coil. A DC armature of a miniature motor (or generator) A partially-constructed DC armature, showing the (incomplete) windings In electrical engineering, the armature is the winding (or set of windings) of an electric machine which carries alternating current. Determine the phase and line voltages if the coil is full pitched. 2. It. (a) Describe armature reaction and explain its effect on terminal voltage (b) Calculate the speed and open circuit line and phase voltages of a 4-pole, 3-3 pitch factor or coil span factor in alternator tutorialspoint web oct 1 2021 1 2 if the coil span of a single coil is less than the pole pitch of 180A two pole three-phase 50 hz wye-connected AC generator has 9 slots per pole and 6 conductors per slot . Share on Whatsapp Latest UPSC IES Updates. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. The primary reason for making the coil span of a d. A. Coil span is 16 – 1 = 15 slots. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. 966 Distribution factor = 0. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2 coil sides per slot. 1. With a full-pitch coil, the emfs induced in the two coil sides are in phase with each other and the resultant emf is the arithmetic sum of individual emfs. ; Coil Span: It is the angular distance between the two sides of the coil. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. If we used short pitched winding for armature winding than pitched factor is included in EMF equation in Alternator. It may be the full pitched or short pitch. The coil span is 150°. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. . Obtain a coil span of 180 degrees (electrical) b. 2. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. The pitch of the coil has 4 slots less than the pole pitch. e. (BTL-1) 4. Pole pitch is always equal to 180o 7. . If the coil span is reduced by one slot, then the phase angle α between the induced EMFs in the two sides of the coil is given as. Commutator pitch. A three phase, 50 Hz, 8 pole alternator has a star connected winding with 120 slots and 6 conductor per slot. • In double layer windings used in. Pitch Factor or Coil Pitch. P. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. In general, electrical degrees equals mechanical degrees times 1/2 the number of poles. IV. Power System Analysis and Design (MindTap Course List) 6th Edition. In such coils, the two coil sides are not under the poles. 8. BUY. 12Wb. The formula for pitch factor is given by The pitch factor in the above equation is for fundamental component of emf. e. If the generator is running at 1200 rpm, find the average voltage generated between brushes for wave winding. 2 Selecting the coil span for a given pole pitch. 15, 13; 19, 17; 21, 19; 23, 21;150° is (frac{5}{6}) parts of 180° i. it is said to the a fractional-pitch coil. Example: the throw could be to 9 meaning that one side of the coil is inserted in slot #1, and the other side in slot #9. 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. 0. A 6-pole, 3-phase, 60 cycle alternator has 12 slots per pole and four conductors per slot. The slots per pole per phase are 8 and the coil span is 20 slots. 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. a. 60 hz, 10-pole alternator has 120 slots and 4 turns in every coil. Number of slots: 3 Number of poles: 2 Number of phases: 3 Number of layers: 1 Coil span : 1 Number of slots per pole per phase: 1/2. M. SEE MORE TEXTBOOKS. The ratio of phasor (vector) sum of induced emfs per coil to the arithmetic sum of induced emfs per coil is known as pitch factor (Kp)or coil span factor (Kc) which is always less than unity. p Number of pole-pairs q Ratio of pole-width to pole-pitch Q Least number of slots in a doubly slotted machine Qs Number of coils per phase of distributed winding Ru Resistance of phase-belt, u = a,b,c R Matrix of branch resistances Sn Cross-sectional area of nth coil T Time-period vu Supply voltage of uth phase-belt, u = a,b,c α Mechanical. As shown in Fig. 4. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. It equals pole pitch = Z P . 5 c) 18 d) 6 View Answer. On the other hand, if its span is less than a pole-pitch. 4 pole = 90º. . A coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below. Front connections 8+7=15; 30+7-30=7 8. Calculate the emf generated in each phase when the machine runs at 375 rpmHence, pitch factor or coil span factor K p = Cos(/2). Emf induced per coil side is E. 40 O 2. Download these Free Coil Span or Coil Pitch MCQ Quiz Pdf and prepare for your upcoming exams Like Banking, SSC, Railway, UPSC, State PSC. If the maximum flux per pole, with a sinusoidal distribution, is 0. the distance between the two sides of coil is called the coil-pitch. If the coil-span (or coil-pitch) is equal to the pole-pitch, then the coil is termed a full-pitch coil. ); and k y is the short pitch factor. The current is in same direction in both the sides of the coil. per slots, in a double layer. Coil Span: It is the angular distance between the two sides of the coil. Please see Electrical 4 U site for article on Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. ∴ e = E 1 + E 2 = 2E. It is given by K p = cos (α/2) Where α is the short pitch or chording angle. 866. the core length 32 cm, and the stator coil span four fifth of the pole pitch. This chapter covers the calculation of winding factors and armature MMFs, harmonic analysis of armature MMFs. In a 10 pole, lap wound de armature, the number of active armature conductor per pole is 50. It is using an armature winding which is short pitched by one slot. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. It may be the full pitched or short pitch. c. The coil-span is 144° (electrical). The coil span should be minimum of about 8. fs. 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. To get a coil around every tooth, we need two winding layers (double layer winding). 4 pole = 90o. What is the pitch factor? Solution: Example 2: A 400 kVA, 6 kV, 60-cycle Y-connected alternator has the following data: poles = 6; conductors per slot = 12; total slots = 54; winding = two-layer lap; pitch = 8/9; flux per pole = 4 x 107 maxwells. Short-pitched coils are deliberately used because of the following advantages: 1. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched coil. Answer: c Explanation: K p =cosε/2 (i) Slots per pole = 36/4=9, for a coil span of 8 slots, the coil is short pitched by 1 slot and the chording angle is ε=γ = 20° ⇒ K p =cos10°=0. 4 Winding Factor Both distribution factor (Kd) and pitch factor Kp together is known as winding factor Kw. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. ∴ e = E 1 + E 2 = 2E. Find the pitch factor for an alternator having 48 stator slots, 6 poles, coil span 1-6 Option 1: cos 45 ° Option 2: cos 24 ° Option 3: cos 34 °. This answer is:Full-pitch windings have a coil pitch of 1, which means the coil span is equal to the pole pitch. A. An 8-pole lap wound DC generator has 120 slots having 4 conductors per slot. 3K views. 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. a. A six pole, three phase AC generator has 72 slots, the coil span is 12. Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature. In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch, back pitch, pole pitch, coil pitch, etc. #10 A 4-pole,3-phase, y-connected induction motor has 48 stator slots 8 series conductors per slot and coil pitch of 83. 363Wb and a 15% third harmonic. air. Determine the pitch (or coil span) factors for the winding ,24 Stator slots ,4 poles, coil span 1 to 5 12. . . K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. There are 2,500,000 Maxwells entering the armature from each North Pole, and this flux is sinusoidally distributed along the air gap. winding is fractional-pitched. Lap and Wave winding. Back pitch (Y b): It is the span of the coil from the back end. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. Lap winding • Suppose we want to make a lap winding for a P = 4 pole D. 9: Rated speed (rpm) 170: Rated current (Arms) 3. . 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. A pole pitch is always 180° electrical regardless of the number of poles on the machine. 2 sin 30+0. If fractional pitch is used, the emfs in the two coil sides are out of phase, which reduces the emf. Thus the total emf at the coil terminal A & B is the phasor sum of (E 1 +E 10), (E. 23. A pole pitch is always 180° electrical regardless of the number of poles on the machine. BUY. 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. 4. (ii) Pole pitch: The over hang portion of the coils depend upon the coil. Winding table. Pitch Factor·· the ratio of the voltage generated in ti1e fractional-pitch coil to the voltage generated in the full-pitch. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° =. b) 96 stator slots, 6 pole, coil span 1 to…. You can compare the maximum fundamental winding factor for different. Determine the phase andline values of emf if the machine runs at 600 rpm and the flux per poleis 0. Fractional pitched windings are purposely used to effect a substantial saving in copper of the end connection and for improving commutation . ’s of consecutive turns c. The flux per pole is 80 m Wb and the coil span is 160° electrical. 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. F. 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. 60o / 90o = 2/3. Coil Span: It is the angular distance between the two sides of the coil. 8. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. Coil – span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 85 lagging. I need answer within 20 minutes please please with my best wishes. Problem. The primary reason for making the coil span of a d. 966the coil span of the two slot‐pitch technique has been pro-posed, based on the ‘stator shifting’ concept [8, 9]. 9 slots . When the coil span is equal to pole pitch (180 deg electrical), the winding is called full pitched winding. All coils in a phase are connected in series. Pole – pitch. Prelude to Synchronous Generator Induced E. A. Determine the coil and commutator pitches for a 72-slot 288-segment six-pole frog-leg armature winding. The coil span is 160°. When measured in electrical degrees one pole itch is equal to 1800. Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. coil span, slip-ring voltage on open circuit, approximate full load current per phase in rotor. Three kinds of coil spans are used, they are 4-solt pitch, 3-solt pitch, and 2-solt pitch. 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. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch, back pitch, pole pitch, coil pitch, etc. Use a diagram like that shown in fig. . It is usually measured in terms of teeth, slots or electrical degrees. 6. 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. When the. Let us assume that, a coil is short pitched by an angle α (electrical degree). The winding is wye-connected. – Comparator. 31. In a 4-pole, 35 slot dc armature, 180 electrical degree coil span will be obtained when coils occupy _____ slots. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. The reduction fraction is the pitch factor. 2. a. 1kv. At this situation, two opposite sides of the coil lie under two opposite poles. armature, 180 electrical. M. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. This lecture will discuss;1. . There are 2 coil sides per slot. For a coil span of 13/15 of a pole pitch, the phase winding factor is: K_p = cos(π * 13 / (2 * 15)) = 0. 4. If the coil span is equal to the Pole pitch then it is called a full pitch coil. 911 V B. 160 degrees b. 967. Both, 7/9 and 8/9, are equally close to 5/6 but I would select 8/9 for better flux utilization. 24, and assume first a short-pitched coil spanning half a pole pitch, then a long-pitched coil spanning one and a half. 1. 150 degree (electrical). In this case, the coil sides lie under opposite poles, hence the induced e. . c. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. Design a suitable double-layer lap winding for a 6-pole armature with 18 slots and two coil-sides per slot. See answer (1) Best Answer. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. 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. Since this machine has 8 poles and a pole-pitch of 48/8 = 6 slots, the coil pitch here is 5/6 = 0·833 p. D. situation, two opposite sides of the coil lie under two opposite poles. To improve the wave form only 80% of the pole pitch is wound. Coil span or coil pitch Ys: It is the distance between the two sides of a coil measured in terms of armature slots. C machine having a total number slots S = 16. The displacement between the sides of the coil is called the coil span. 0. If the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. Pole pitch = 180 electrical degrees = S/P = 2C/P. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. ( b) 42 stator slots, four-poles, coil. 98: 61. fs. The coil span or coil pitch for short or fractional pitch coil is less than 180 electrical degrees. With a full-pitch coil, the emfs induced in the two coil sides are. The pitch factor, in rotating electrical machinery, is. 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. pitch factorThe flux distribution Curve of a smooth-core 50 c/s generator is. This video lecture provides full understanding of pole pitch and coil pitch with examples. Coil Span: It is the angular distance between the two sides of the coil. The coil used in double layer winding are diamond shaped as in the dc windings. 0 B. 26. In this case, there is a phase difference between the e. IMs designed by utilising the winding configurations given in Section 3 are analysed and both SS and FW performance characteristics are presented. Hence emf induced in one side of. 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 ____________. pole pitch. are e. armature, 180 electrical-degree coil span will be obtained when coils occupy. is known as coil span. of slots / slots per pole. 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. Q: 3- Determine the coil span for 3-phase, two pole alternator, the pole pitch is equal to 18 slots and… A: For a two-pole alternator,Pole pitch = 18 slotsCoil span factor =32 Q: A 4 pole, three-phase, star-connected alternator has an armature with 120 slots and 4 conductors per…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. Calculate its coil span factor. Determine the equation for the emf induced in one turn, and its RMS value. Transcribed Image Text: (d) obtain a full-pitch winding. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. Better emf waveform in case of generators 6. If the coil span is equal to the Pole pitch then it is called a full pitch coil. If the coil span is equal to the Pole pitch then it is called a full pitch coil. If the coil span is equal to the Pole pitch then it is called a full pitch coil. the coil span is (180-ε), therefore the emf induced in these coil sides will also be separated by this angle. Transcribed Image Text: (d) obtain a full-pitch winding. For alternator having fractional pitch winding of 8/14 the coil span is 102. Calculate the distribu factor for a 36-slot. 0. If the coil pitch is less than one pole pitch, the coil is called the short-pitch coil or fractional-pitch coil. , Y = 2/3 τ p. Despite its disadvantages, it is common in mass production. For a 3-phase winding with 5 slots per pole per phase and with a coil span of 12 slot pitch, the value of pitch factor is. where: coil. The coil span is 150 electrical degrees. K p = cos (nα/2) Where n is the nth harmonic. We will start Red at slot 1. The separation between the top and bottom sides of a coil is called Coil span. (Assume lap. 0. Determine the number of conductors in series per phase. Where n is the nth harmonic. 10. 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. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. e. Calculate the emf generated in each phase when the machine runs at 375 rpmHey Aspirants. coils having span which is equal to one pole-pitch i. arrow_forward. 966 D. ( ) () ⎪ ⎪ ⎪ ⎩ ⎪⎪ ⎪ ⎨ ⎧ = − = − = − = − = sin 8 /5 sin 6 /5 sin. The coil span factor is represented as For full pitch coil, the value of α will be 0⁰, cos α/2 = 1 and KC = 1. Calculate the rms value of the induced emf/phase of a 10 pole, 3 , 50 Hz alternator with and in 2 layers. The resultant coil voltage $𝐸_{𝐶}$ is equal to the phasor sum of $𝐸_{𝐶1}$ and $𝐸_{𝐶2}$. Share on Whatsapp India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses. 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. , Y R = Y B − Y F . F = 0. Short-pitched coils are deliberately used because of the following advantages: 1. If the coil span is exactly equal to the pole-pitch, then such a coil is called a full-pitch coil. coil pitch in terms of electrical angle3. The pitch of the coil is 2 slot less than the pole pitch. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. EE - 422 DC & AC MACHINERY 2nd Semester AY 2020-2021 ENGR. Calculate its coil span factor. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. P i t c h f a c t o r = W i n d i n g f a c t o r P o l e p i t c h. p. 26. e. Then, the pitch factor will be equal. per Phase: Part 1In this video, I'll give you an idea how to derive the fundamental pitch factor (coil span f. No matter how many poles, each pole always spans exactly 180 electrical degrees, and it is called pole pitch. This distance is measured in terms of armature slots or armature conductors that come between two. Coil is 12 slots. e. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. Pole pitch is always equal to 180o. 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. Comparator. Study with Quizlet and memorize flashcards containing terms like A lap winding, Twice, Full-pitch and more. Front pitch (Y f):.