• So coil span is 16/4 = 4. b) 96 stator slots, 6 pole, coil span 1 to…. IMs designed by utilising the winding configurations given in Section 3 are analysed and both SS and FW performance characteristics are presented. 24, and assume first a short-pitched coil spanning half a pole pitch, then a long-pitched coil spanning one and a half. e. 086 Wb, what will be the values of the emfs? phase. To get a coil around every tooth, we need two winding layers (double layer winding). (d)Find the number of turns per phase, Tph. Key. coils having span which is equal to one pole-pitch i. Determine both the winding factor and the effective turns per phase. Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature. Pole – pitch. Coil span is 16 – 1 = 15 slots. 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 °. The coil span is 150 , the flux/pole has a fundamental components of 0. The commutation is improved in short-pitched coil, but the emf induced will be less compared to full-pitch. e. Each of these coil spans is five slots, so this choice of winding. What is the coil span for a 2 pole 18 slot machine? a) 9 b) 4. Alternatively, this type of coil is also called a short-pitch or chorded coil. The formula for pitch factor is given by The pitch factor in the above equation is for fundamental component of emf. If the coil span is less then one pole pitch than it is called short pitch coil. 958] (B) Determine the maximum flux per'pole when connected to a' 220-volt,60-cycle line, neglecting local resistance and reactance drops. If the coil span is less than the pole pitch (as in coil B where coil pitch is 3/4th of the pole pitch), then the Fig. 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. , pole-pitch ) is known as 'Full Pitch'. Winding table. The width of the coils is 5/6 of the pole pitch. 5. it is defined as the peripheral distance between the center of two adjacent poles in a DC machine. Back pitch (Y b): It is the span of the coil from the back end. The coil pitch is 12/15. As the two coil sides are separated in space by an angle of (180-ε) i. 259 C. The pole pitch, S/P, is also fractional, so that the coil-span cannot be of full-pitch. 15. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. • To view the coil sides / coils, we must look below from above the slots as depicted in figure. Coil spanA: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. 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. . There are 2 coil sides per slot. For a full pitch coil, the value of pitch factor is unity whereas for its value is also unity for concentrated coils. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. The coil span is 150°. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. CONTENTS CONTENTS + 0 ) 2 6 - 4 Lear ningPole – pitch. 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. 75), the lowest 2-solt coil span. Coil–span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. , or 5/6 × 180° = 150 electrical degrees. Calculate the pitch and distribution factors for the fundamental, the third, and the fifth harmonics in the phase voltage. Learn what a pole pitch is, the pole pitch formula & definition, and how to. If we used short pitched winding for armature winding than pitched factor is included in EMF equation in Alternator. The pole pitch is 35 cm. m. It is one pole pitch. 5. 05 Wb, sinusoidally distributed. (16) k p1 = sin β 2 <1 where β is the coil span in °electrical, β=sα; s is the coil span in slots. The primary reason for making the coil span of a d. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. Solution : Coil groups per phase = 3 x 4 = 12 Slots per pole per phase, m =24/12 =2 Angle between adjacent slots, â =180/24 =30 For full pitch coils, the coil span, á = 0, ie. poles, 18 slots alternator, the pole pitch is n = 18/2 = 9 slots. In a synchronous generator, what do fractional pitch and fractional slot windings mean?• (e) The coil span must be odd integer. 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 ____________. 9780133923605. What is the short pitch in electrical degrees. Hence emf induced in one side of. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. C machine having a total number slots S = 16. Advantages of short pitched,( chorded, fractional slot) windings are:-The amount of copper used in the overhang (end winding) reduced and hence a saving on copper,Based on pitch of the coil (i) full pitched (ii) short pitched windings. The coil pitch is 5/6th of the full pitch and the flux per pole is o. In a fractional pitch winding, the coil span is made less than 180 degrees electrical space. Pitch Factor or Coil Pitch. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. I need answer within 20 minutes please please with my best wishes. The coil span A. – Comparator. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. In practice, coil pitch (or Span) as low as eight-tenths of a Pole Pitch, is employed without much serious reduction in emf. Distribute the winding uniformly under different poles d. See solution. ; Coil Span: It is the angular distance between the two sides of the coil. Create a winding table for the given armature: Winding 1: 4 pole, 11 slots, 11 commutator segments, double layer, progressive, simplex WAVE winding Show the solutions. 60o groups, 2-layer winding is used. . View full document. Coil – span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 6. of slots/pole/phase, m = 4 ma 2x30 ata Soest 0-9659 (Ans. There are 4conductors per slot and a sinusoidally distributed flux per pole of 36mWb. 9659. Let us assume that, a coil is short pitched by an angle α (electrical degree). in. 866. Author: Frank D. g. For the n th harmonic, the chording angle becomes nα° electrical. what is coil pitch or coil span. Pole arc/ pole pitch = core length/ pole pitch = 0. The length of the mean turn depends on the following factors (i) Gross length of the stator core: Each turn consists of two times the gross length of stator core. Its magnetic poles can be salient (protruding or sticking out from the surface of the rotor), as shown in Fig. the core length 32 cm, and. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. 966 D. If the coil span is less than the pole pitch then the coil is said to be a short-pitched 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. 0 D. 4. Pole – pitch. 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. (a) multiplex (b) fractional-pitch (c) full-pitch (d) pole-pitch 3. Find the breadth factor for 3-Iwinding with 2 slots per pole per phase. Pole and slot numbers. 1kv. 951, 0. Corresponds to 180/12 i. Similarly, if the emf induced in coil sides 2 and 11 are E 2 & E 11, then the total emf in coil 2-11 is given as arithmetic sum of E 2 and E 11. Pole pitch is the peripheral distance between two adjacent poles. fs. by 20o to full pitch distance. The part of the coil in which EMF is generated is known as _____. However the waveform of the resultant emf can be improved by making the. When two capacitors of reactances 10ohms and 20 ohms are connected in parallel across a 100 V supply, total VAR drawn will be _. B. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Pitch factor: Pitch factor is defined as the ratio of the induced emf per coil when the winding is short-pitched to the induced emf per coil when the winding is full pitched. Calculate the emf generated in each phase when the machine runs at 375 rpm Hey Aspirants. 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. What is the flux per pole if the voltage on open circuit is 1. 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. The slots per pole per phase are 8 and the coil span is 20 slots. 13. Get Coil Span or Coil Pitch Multiple Choice Questions (MCQ Quiz) with answers and detailed solutions. If the coil span factor is 0. The coil span of the alternator is 1 to 8. 4 pole three phase winding. 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. the coil will be in 180o. it is said to the a fractional-pitch coil. K p = cos (nα/2) Where n is the nth harmonic. Determine the pitch (or coil span) factors for the winding ,24 Stator slots ,4 poles, coil span 1 to 5 12. But, the given coil is short-pitched so that the coil span is $$\mathrm{coil\:span = (14 − 1)β = 13β}$$ $$\mathrm{∴\:α = (15 − 13)β = 2β = 2 × 12° = 24°}$$ Winding factor for fundamental component Pole pitchis defined as the peripheral distance between the center of two adjacent poles in a DC machine. Determine the equation for the emf induced in one turn, and its RMS value. The first coil lies in slots 1 and 16. Boylestad. Full Pitch and. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. 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. The coil span is five-sixth of a pole pitch. Kr ==sink 2 · Kp =pitch factor in dcci111al p" =span of the coil in electrical degrees. Show transcribed image text There are 3 steps to solve this one. 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 3rd harmonics. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. For n th harmonic. Pole pitch. 1. Hence, during rotation when one side of the coil comes under north pole, the other side of the coil comes under south pole. If coil span is equal to pole pitch then it is called full pitch coil. g. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. The. = 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. Transcribed Image Text: 9. (In general, Y C = ± m) 5. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. Pole pitch is always equal to 180o. Coil span σ, winding factor k w, pole ratio G r and N c for possible pole-slot combinations in the proposed FMPM machine. The alternator has 18 slots per pole and the first coil lies in slots 1 and 16. Pole Pitch: It is the angular distance between the two adjacent poles. Fig. 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/. 0 B. 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. ∙ 10y ago. . Calculation:When the coil sides forming a coil are spaced exactly one pole pitch a part they are said to be of full-pitch. In SWAT-EM we can set the coil span explicite. The value of α will usually be given in the question, if not, then assume kc = 1. the coils cannot be full - pitched; they may be short - pitched with 15 slots, or long - pitched with 16 slots. The coil span is 150 electrical degrees. For a full pitch coil, the value of pitch factor is unity whereas for its value is also unity for concentrated coils. To get a coil around every tooth, we need two winding layers (double layer winding). The winding is wye-connected. Coilspan or coil-pitch. 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. Sanfoundry Certification Contest of the Month is Live. m. 966the coil span of the two slot‐pitch technique has been pro-posed, based on the ‘stator shifting’ concept [8, 9]. 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. 7. For n th harmonic. m. 015 Wb. , pole-pitch ) is known as 'Full Pitch'. When the winding is full pitched, coil span is equal to the pole pitch. 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. In other words, the distance between the two coil sides of a coil will be equal to the distance. The induced emf in each coil side. 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. a coil. This answer is:Full-pitch windings have a coil pitch of 1, which means the coil span is equal to the pole pitch. 0 B. It may be the full pitched or short pitch. can never be equal to pole pitch D. number of slots and a coil span of two slots require at least 18 slots. in the two sides of the coil. (ii) Pole pitch: The over hang portion of the coils depend upon the coil. 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. A pole pitch is always 180° electrical regardless of the number of poles on the machine. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. 5. 14. armature, 180 electrical-degree coil span will be obtained when coils occupy. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. 2:. Solution for For alternator having fractional pitch winding of 10/14 the coil span is 4. Now labeling the starting end of each coil is easy,. The coil span is 150°. 26. The coil span is 150 electrical degrees. 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. 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). Compared to the overlapping winding above we need only 3 slots for the two poles. ISBN: 9780133923605. Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span), by the number of slots per pole. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. m. P˚ Kp = sin [(90°)(pitch)] Kp = sin 𝟐 PROBLEM 1: A 6 pole, 3Φ AC generated has 72 slots, the coil span is 12. It is usually measured in terms of teeth, slots or electrical degrees. There are 2,500,000 Maxwells entering the armature from each North Pole, and this flux is sinusoidally distributed along the air gap. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. We make the coil span less than 180 degrees electrical space degrees in a fractional pitch winding. per slots, in a double layer. Find the terminal voltageon open circuit. 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. arrow_forward. Better emf waveform in case of generators 6. 1. Condition for designing a Mush winding:- 21. Pitch: Pole and Winding • Pole pitch is the mechanical angle between adjacent poles, e. round the coil which is the vector sum of e. Draw the developed diagram andshow the positions of brushes. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. The correct answer is option 2): 5 slots Concept: Coil span (also known as coil pitch) is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them. A 4-pole, 3-phase synchronous machine has 48 slots. AC compound generator usually has lower resistance. Prob. If the coil span is equal to the Pole pitch then it is called a full pitch coil. 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. There are 0. A coil has a pitch of 10 slots instead of 12 slots in the figure above, so its spread is no longer equal to pole pitch. The coil used in double layer winding are diamond shaped as in the dc windings. The coil span is 160°. Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding. 985 (ii) Slots per pole = 72/6=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° ⇒ K p =cos15°=0. 10 slots d. fs. Study now. 5. . β = 180o/ = 20o. 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. 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. Note. *. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. The pitch factor for third harmonic in an alternator having 18 slots per pole and coil span 5/6 of pole pitch is _. First. Author: Robert L. A 3-phase, 50 Hz, 2-pole, star connected turbo alternator has 54 slots with 4 conductor per slot. Pole Pitch: It is the angular distance between the two adjacent poles. • Coil span is nothing but the spacing between the two coil sides of a coil. The pole pitch is 35cm, the core length is 32cm & sta- 4th tor coil span is of pole pitch. Calculate the armature winding distribution factor. 26. When the coil is having a span of less than 180° electrical, it is known as a short-pitch coil. In SWAT-EM the coil span is given in number of slots. Pole Pitch, Coil Span, Back Pitch, Front Pitch, Commutator Pitch in Armature Winding of DC Machines are explained in this video. The slots per pole per phase are 8 and the coil span is 20 slots. 15. Use a diagram like that shown in fig. K pn = cos nα/2. For A. 0. The pole pitch is always 180 degrees electrical regardless of the number of poles in a machine. Pole pitch is the electrical angle between the north pole and. Where n is the nth harmonic. phase shift with emf induced in the other side of the coil. The arc diagram contains all the necessary information for connecting the pole-groups correctly. When the coil span of the winding is equal to pole pitch, the coils are called the full pitched coils. m. Looking at the diagram in the question. Let n be the number of slots per pole. So if coil side in slot No. Question. 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. 3 percent. Download these Free Coil Span or Coil Pitch MCQ Quiz Pdf and prepare for your upcoming exams Like Banking, SSC, Railway, UPSC, State PSC. Pitch Factor·· the ratio of the voltage generated in ti1e fractional-pitch coil to the voltage generated in the full-pitch. 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. 2. Pole pitch is always equal to 180o. 2. Pole pitch is always equal to 180o electrical. Calculared the flux per pole required to give Il kV line voltage on open circuit voltage. See moreIf the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. A Three-phase four-pole AC machine has 60 coils in the stator and each coil has 100 turns. For alternator having fractional pitch winding of 8/14 the coil span is 102. If fractional pitch is used, the emfs in the two coil sides are out of phase, which reduces the emf. f. If the coil span factor is 0. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. m. 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. 851: D) 0. It is sometimes convenient to speak of an armature coil span as having a fractional pitch expressed as a fraction e. . 09 O4. The short equidistant winding of 48 grooves, 4 pole three phase asynchronous motor individual layers of the present invention is totally 12 groups of coils, and every group of coil is comprised of two coils; The pitch of all coils, shape and size are all identical, and coil span is 9; And adopt overlapping method rule and Salient pole. 0. of consecu- tive turns (c) distribute the winding. Draw the double layer winding layout for a 24 slot stator and 4 pole alternator 3. (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 . • Winding pitch is the coil span divided by the pole pitch, e. It is lesser than the value in the first case. 1 times the pole arc. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. 11. Generally. 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. round the coil which is the vector sum of e. C. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. 9 slots . coil pitch in terms of slots4. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 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. 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. 6. F. 455 V D. the flux per. The flux per pole has a fundamental component of 0. frame. If S be the total number of slots and P be the total number of poles then coil span is S/P. A. 966 and 0. First. If the coil span is less then one pole pitch than it is called short pitch coil. Coil–span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. , coil span is 180º electrical) is called a full-pitch coil. 6-phase fractional-slot-per-pole-per-phase Interior Permanent Magnet (IPM) machine having a novel topology of 18-slot, 8-pole, and, 6-phase, 48-slot, 8-pole IPM with distributed windings, both. Back. (5/6) of a pole pitch. Its value is always less than unity. It means that coil span is 180 electrical degrees.