Key. 11. 0. 4 pole = 90o. A. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched coil. The highest winding factor can be obtained with 4-solt span coil (the coil span is closest to pole pitch 3. . The pole pitch is defined as the distance between two consecutive poles. Full Pitch and. It equals pole pitch = Z P . fs. 3K views. The coil span should be minimum of about 8. 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. When a coil. • Coil span is nothing but the spacing between the two coil sides of a coil. 966 and 0. F. If the coil span is less then one pole pitch than it is called short pitch coil. Prelude to Synchronous Generator Induced 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. Pole pitch is always equal to 180o. Hence, the total e. Pole pitch is always equal to 180o. Pole – pitch. The coil span of a full pitch coil is always 180° electrical. Share on Whatsapp Latest UPSC IES Updates. Assume the coil span as 150° electrical. (d)Find the number of turns per phase, Tph. 👉 (2008-2018) With solution, BRANCH Wise Click the Link-ELECTRICAL. Coil span is defined as the peripheral distance between two sides of a coil. 150 degree (electrical). Hence, the total e. It is usually measured in terms of teeth, slots or electrical degrees. Learn what a pole pitch is, the pole pitch formula & definition, and how to. Calculate the emf generated in each phase when the machine runs at 375 rpm Hey Aspirants. 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. 966 D. The coil-span chosen is of course less than the full-pitch. If the coil pitch is less than one pole pitch, the coil is called the short-pitch coil or fractional-pitch coil. situation, two opposite sides of the coil lie under two opposite poles. The pole pitch is 35 cm. Determine both the winding factor and the effective turns per phase. 2. pdf from CSE 302 at World University of Bangladesh. How do you calculate winding pitch? Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span) , by the number of slots per pole. Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. In a 4-pole, 35 slot d. spanning over 180° (electrical). Coil span or Coil Pitch. 1 . This is shown in the figure to left. Pole pitch is always equal to 180o. m. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. Draw the double layer winding layout for a 24 slot stator and 4 pole alternator 3. Concept: Coil pitch or coil span: It is defined as the angular distance between the two coil sides of one coil. TABLE I Winding factors for different combinations of pole numbers p and slot numbers Qs Qs p 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42. The pole pitch is 35 cm. m. Relation between frequency, speed and number of poles: Fig: 1. 2-pole star-connected, armature winding of a generator has 6 slots per phase. However, the phase winding factor for short-pitched coils is different from that of full-pitch coils. The highest flux we get, if we define the coil span equal to the pole pitch . arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. Coil pitch or coil span is defined as the angular distance between the two coil sides of one coil. 3 percent. m. 26. In such coils, the two coil sides are not under the poles. Share on Whatsapp India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses. . in. It means that coil span is 180 electrical degrees. This type of winding is mainly used for. In practice, coil pitch (or Span) as low as eight-tenths of a Pole Pitch, is employed without much serious reduction in emf. Better emf waveform in case of generators 6. o. Pitch Factor·· the ratio of the voltage generated in ti1e fractional-pitch coil to the voltage generated in the full-pitch. 4 Winding Factor Both distribution factor (Kd) and pitch factor Kp together is known as winding factor Kw. There is a formula for calculating electromagnetic torque based on magnetic flux, distribution factor, and pitch factor [18] as equation 8. The dc armature winding in which coil sides are a pole pitch apart is called ____ winding – Full- pitch. The pitch factor. If the pole span or coil pitch is equal to the pole pitch (as in the case of coil A where pole-pitch of 4 has been. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. The coil span is 150°. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. 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. For a coil span of 13/15 of a pole pitch, the phase winding factor is: K_p = cos(π * 13 / (2 * 15)) = 0. ∴ e = E 1 + E 2 = 2E. 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. fs. 1. 86. Note. , pole-pitch ) is known as 'Full Pitch'. It is always 180° electrical. . 2. 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. Assume = 0. This chapter covers the calculation of winding factors and armature MMFs, harmonic analysis of armature MMFs. To improve the wave form only 80% of the pole pitch is wound. ISBN: 9780073373843. (ii) Pole pitch: The over hang portion of the coils depend upon the coil. 2 sin 50 +0. (A) Determine the pitch and distribution factors. 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. Generators 897. . ; Coil Span: It is the angular distance between the two sides of the coil. , Y R = Y B − Y F . 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. a. e. 85 lagging. 455 V D. The alternator has 18 slots per pole and the first coil lies in slots 1 and 16. See moreIf the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. Here, e = E 1 = E 2 = E. The usefulness of winding distribution and chording in reducing or eliminating harmonics will be touched on in. With a full-pitch coil, the emfs induced in the two coil sides are. Better emf waveform in case of generators 6. The arithmetic sum of induced emfs is 2E. 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. Author: Frank D. M. 15. Lap winding • Suppose we want to make a lap winding for a P = 4 pole D. Pole – pitch. • Key design factors include number of poles, number of slots, and number of slots spanned by coils. Allow 10 ampere for the field current and assume a voltage drop of 4 volts for the armature circuit. BUY. To get a coil around every tooth, we need two winding layers (double layer winding). Calculate the emf generated in each phase when the machine runs at 375 rpmHence, pitch factor or coil span factor K p = Cos(/2). Fractional pitched windings are purposely used to effect a substantial saving in copper of the end connection and for improving commutation . The slots per pole per phase are 8 and the coil span is 20 slots. 12 Wb and a. Determine the phase andline values of emf if the machine runs at 600 rpm and the flux per poleis 0. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. 15. There are 4conductors per slot and a sinusoidally distributed flux per pole of 36mWb. it is said to the a fractional-pitch coil. When the coil span of the winding is equal to pole pitch, the coils are called the full pitched coils. armature winding equal to a pole pitch is to (a) obtain a coil span of 180° (electrical) (b) ensure the addition of e. . Chording: with coil-span less than pole pitch 5. pole pitch. In other words, the distance between the two coil sides of a coil will be equal to the distance. For n th harmonic. m. The winding distribution factor of the alternator is. 1NP2. Commutator bars per pole. 707 B. winding is fractional-pitched. 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 ____________. 15. So if coil span is ‘n’ slots or 180° electrical the coil is called 180° full pitch coil. e. arrow_forward. by 20o to full pitch distance. #Alternator #Protectionofalternator#elect. The pitch factor [3], [6], [7], [8] is the ratio of coil voltages for a fractional-pitch winding to those for a full-pitch one. The pole arc should be about 70% of pole pitch and length of core about 1. 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. Calculate its coil span factor. 57. 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. 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. This number is known as coil span. slots. As shown in Fig. For making coil span equal to a pole pitch in the armature winding of a d. It may be the full pitched or short pitch. The primary reason for making the coil span of a d. When measured in electrical degrees one pole itch is equal to 1800. of a 10-pole three-phase 50Hz alternator with 2 slots per pole per phase and 4 conductors. This is naturally equal to the total number of armature slots divided by the number of poles in the machine. The coil span is 150 , the flux/pole has a fundamental components of 0. Equation () represents the operating magnetic load line of the PMSG, which is a function of machine dimensions; such as radius, stack length, air gap length and PM thickness. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. generator, the back pitch of the winding must equal the number of (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. Its value is always less than unity. In general, if the coil span falls short of full-pitch by an angle α (electrical)*, then kc = cos α/2. For a full pitch coil, the value of pitch factor is unity whereas for its value is also unity for concentrated coils. 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. Emf induced per coil side is E. It is usually measured in terms of teeth, slots or electrical degrees. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. D. A. the flux per pole has a fundamental component of 0. Download Solution PDF. 851: D) 0. 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. It is using an armature winding which is short pitched by one slot. Muthu RE: How. armature, 180 electrical-degree coil span will be obtained when coils occupy. However the waveform of the resultant emf can be improved by making the. Please see Electrical 4 U site for article on Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. 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. poles, 18 slots alternator, the pole pitch is n = 18/2 = 9 slots. For 20 slots, 4 polesThe winding of a 4-pole alternator having 36 slots and coils and a coil span of 1 to 8. K pn = cos nα/2. 6. Question: 2 Problem 2: The flux distribution curve of a smooth core 50HZ generator is B(0) = sin 8 +0. Coil span and commutato pitch b. There are 0. † ‡ ˆ ‰ Š ‹ Œ Ž ‘ ’ “ ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿPitch factor: Full-pitched coils i. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. 0. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. c. 125 Wb and a 25% third component. 160 degrees b. m. ( ) () ⎪ ⎪ ⎪ ⎩ ⎪⎪ ⎪ ⎨ ⎧ = − = − = − = − = sin 8 /5 sin 6 /5 sin. machines with. It has key variables such as Pole Pitch (back and front pitch, resultant pitch and communicator pitch, Coil Span, Commutator Pitch. When two capacitors of reactances 10ohms and 20 ohms are connected in parallel across a 100 V supply, total VAR drawn will be _. Pole – pitch. It is using an armature winding which is short pitched by one slot. B. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. The coils are place in 60 uniformly distributed slots around the inner perimeter of the stator. Download these Free Coil Span or Coil Pitch MCQ Quiz Pdf and prepare for your upcoming exams Like Banking, SSC, Railway, UPSC, State PSC. the core length 32 cm, and the stator coil span four fifth of the pole pitch. In SWAT-EM we can set the coil span explicite. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Condition for designing a Mush winding:- 21. It is one pole pitch. M. 9780133923605. Transcribed Image Text: (d) obtain a full-pitch winding. The coil span is 160°. m. The distance between the two sides of an individual coil of and AC armature winding id termed the coil pitch. m. 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. , 5 slot‐pitches in Figure 2a) [8, 9]. When measured in electrical degrees one pole itch is equal to 1800. Pole pitch = 180 electrical degrees = S/P = 2C/P. u. Calculate the pitch factor for an alternator winding with 36 slots, 4 poles, and coil span of 1 to 8. For a short pitch coil KC. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . It is lesser than the value in the first case. A three phase, 50 Hz, 8 pole alternator has a star connected winding with 120 slots and 6 conductor per slot. 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. 125 Wb and a 25% third component. 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. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. Explanation: Pole pitch is called as center to center distance between two adjacent poles. P˚ = Pitch = coil span in no. 0:00 / 15:33 What is Coil Pitch and Pole Pitch /what is electrical and mechanical angle in Urdu/Hindi IK LECTURES 2. 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. When a coil is having a span of 180° electrical, it is called a full-pitch coil. In a 4-pole, 35 slot d. 15 situated at the center of an N pole rotating in clockwise direction. When the coil is having a span of less than 180° electrical, it is known as a short-pitch coil. 7. b. 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. #Alternator #Protectionofalternator#elect. 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. g. e. g. The arc diagram contains all the necessary information for connecting the pole-groups correctly. e. At this situation, two opposite sides of the coil lie under two opposite poles. advertisement. The pole pitch is 35 cm, the core length 32 cm, and the stator coil span four fifth of the pole pitch. Coil Span:The angular distance between the centers of two adjacent poles on a machine is known as pole pitch or pole span. Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. The use of windings with a coil span of two slots promises a better balance between ohmic losses and end windings space on the one hand and harmonic content. See solution. 4. A 4-pole, 50 Hz alternator has double layer winding with 10 turns per coil and number of slots are 60. = pitch factor or coil span factor ? = ratio of coil span and pole pitch ? = angle of short pitch ? = slots per pole ? = slots? = poles? = short pitch 𝑐 = coil span Distribution Factor, Breadth Factor, Winding Factor, Spread Factor (Kd) Similar to full pitch coils, concentrated winding is also rare in practice. Introductory Circuit Analysis (13th Edition) 13th Edition. 33 percent of pole pitch to obtain the maximum reduction of harmonics. Por a full-pitch coil, Kr = I (unity) r:or a fractional-pitch coil, Kr < 1 6. ( 2) The harmonic voltages decrease in a short pitch coil, thereby improving the waveform of the induced voltage in the winding. e. Pole – pitch. The coil-span is 144° (electrical). The pole pitch is 35 cm, the core length 32 cm, and the stator coil span coil span four fifth of the pole pitch. Its magnetic poles can be salient (protruding or sticking out from the surface of the rotor), as shown in Fig. We must note that the coil-pitch and flux barriers of the NC2 are adjusted as shown in. Problem 1 : Develop the layout of a lap winding for a 3 phase ac machine having 4 pole and 24 slots. Coil span or Coil Pitch. The flux per pole has a fundamental component of 0. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Pole Pitch, Coil Span, Back Pitch, Front Pitch, Commutator Pitch in Armature Winding of DC Machines are explained in this video. View 26 DC Generator. This distance is measured in terms of armature slots or armature conductors that come between two adjacent pole centers. The harmonic reduction in the voltage waveform of concentrated winding axial field PM machines is the subject of interest for many researchers. Calculate the emf generated in each phase when the machine runs at 375 rpmHey Aspirants. It is always equal to 180° electrical. 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. Hence, the pole pitch of that DC machine would be 24. fs. For n th harmonic. The back pitch and front pitch adopted could be respectively. It is given by K p = cos (α/2) Where α is the short pitch or chording angle. A 4 pole, 12 slot lap wound dc armature has two coil side per slot. air. (a)Find the total number of coil groups in the machine. F induced in the other side of the coil. 339 IC function as. It is also called a chorded coil. Discuss the effect of making the coil span very different from the pole pitch on (a) the coil emf and (b) the coil torque. Pole pitch = 180 electrical degrees = S/P = 2C/P. 0 C. In this case, there is a phase difference between the e. In order to eliminate, for example, the third harmonic, as the most significant one, the coil span should be equal to 2/3 of the pole pitch, i. They are two basic physical types for the windings. 086 Wb, what will be the values of the emfs? phase and line? I need the procedure to get to that answer. It is usually measured in terms of teeth, slots or electrical degrees. g. 86 O 119. 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. Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. 5, then the coil-span can be either 11 or 10 slots. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. It is always less than unity. Thus, the total. Transcribed Image Text: 9. As against this if coils are used in such a way that coil span is slightly less than a pole pitch i. The flux per pole has a fundamental component of 0. 966 Distribution factor = 0. coil pitch in terms of slots4. Answer: a. 086 Wb, what will be the values of the emfs? phase. 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 ). Ensure the addition of e. 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). 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. A. It may be the full pitched or short pitch. 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). 363Wb and a 15% third harmonic. The average pitch Y A = 2 B F Y Y +. The individual coils may have a span greater or less than a pole pitch but the average coil-span equals one pole-pitch. The random wire placement leads to a wider distribution of resulting wire length on the coil body and consequently a wider range of electric coil resistances. Design a suitable double-layer lap winding for a 6-pole armature with 18 slots and two coil-sides per slot. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. . There are 2,500,000 Maxwells entering the armature from each North Pole, and this flux is sinusoidally distributed along the air gap. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. . 163Wb. A 3 phase 1800 kVA, 3 kV, 50 Hz, 250 rpm, salient pole. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. Zoom In Zoom Out Reset image size. Generators 897 winding is fractional-pitched. Determine the number of conductors in series per phase. 14. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. Based on number of layers (i) Single layer. (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. Short Pitch Coil. TYPES OF AC MACHINES WINDINGS. Coil spanA: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. It indicates how the coils are spaced out on the armature core. Coil Span: It is the angular distance between the two sides of the coil. 4. Y-connected alternator has 9 slots per pole and a full-pitch. Sanfoundry Certification Contest of the Month is Live. where B is the flux density, µ is permeability of material, A is the area of the magnetic field path, whereas the same subscript used in is used thought the paper. p. For a simplex lap winding, the commutator pitch YC = 1 and coil span YS ~ pole pitch. 25 O 5. Note.