The two sides of a coil are places in two slots on stator surface. c. Assuming single turn coil, calculate the back pitch for progressive and retrogressive winding. The coil span is five-sixth of a pole pitch. It is always equal to 180° electrical. For the n th harmonic, the chording angle becomes nα° electrical. Here we have a 4-pole alternator with a 48 slot stator. 1 the coil span should be approximately equal to a pole pitch. what is coil pitch or coil span. 8 slots b. The conductor being situated at the place of maximum flux density will have maximum emf induced in it. The flux per pole has a fundamental component of 0. It is expressed in terms of electrical space degree. If the span of the coil is reduced by an angle 'α' of electrical, then the. Pole Pitch: It is the angular distance between the two adjacent poles. If the maximum flux per pole, with a sinusoidal distribution, is 0. the flux per pole has a fundamental component of 0. So if coil side in slot No. What are the different types of stator windings in induction motor? Ø. 966 and 0. Short pitch coil: If the angular distances between the two coil sides are less than one pole pitch, it is termed a short pitch or fractional pitch coil. It may be the full pitched or short pitch. Result Number of. Figure 4 shows the flux distribution linked to a short-pitch coil. When two capacitors of reactances 10ohms and 20 ohms are connected in parallel across a 100 V supply, total VAR drawn will be _. 1. *. 1. Let us consider, the coil has a pitch short by an angle α electrical degrees from the full pitch. pitch factor and distribution factor in alternator | coil span factor in hindi | short pitch coilOTHER TOPICS 1) distribution factor in alternator the pole span or coil pitch is equal to the pole pitch (as in the case of coil A in Fig. Condition for designing a Mush winding:- 21. If the coil span is. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. In a synchronous generator, what do fractional pitch and fractional slot windings mean?• (e) The coil span must be odd integer. If the coil span is equal to the Pole pitch then it is called a full pitch coil. In SWAT-EM we can set the coil span explicite. 1 and No. Coil–span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-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. 1, or nonsalient (flush with the surface of the rotor), as shown in Fig. the coil span is (180-ε), therefore the emf induced in these coil sides will also be separated by this angle. ∴ e = E 1 + E 2 = 2E. coil pitch in terms of electrical angle3. A pole pitch is always 180° electrical regardless of the number of poles on the machine. The width of the coils is 5/6 of the pole pitch. Assuming double turn coil, Calculate the back pitch for progressive and retrogressive winding. 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. Transcribed image text: 1. As the two coil sides are separated in space by an angle of (180-ε) i. If the angular distances between the two coil sides are less than one pole pitch, it is termed short pitch or fractional pitch coil. 9 slots . Answer: a. Electricity for Refrigeration, Heating, and Air Conditioning (MindTap Course List). It. Both Y B and Y F should be nearly equal to a pole pitch. 12. Concept: Coil pitch or coil span: It is defined as the angular distance between the two coil sides of one coil. Let us assume that, a coil is short pitched by an angle α (electrical degree). The spacing is expressed in terms of number of slots between the sides. 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. α = Angle of short pitch = 20o. 15, 13; 19, 17; 21, 19; 23, 21;150° is (frac{5}{6}) parts of 180° i. in the two sides of the coil. The harmonic reduction in the voltage waveform of concentrated winding axial field PM machines is the subject of interest for many researchers. A three phase, 50 Hz, 8 pole alternator has a star connected winding with 120 slots and 6 conductor per slot. A six pole, three phase alternator has 72 slots and a coil span of 1 to 10, is the pitch factor? A. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. , Y R = Y B − Y F . When the coil is having a span of less than 180° electrical, it is known as a short-pitch coil. e. 707. It indicates how the coils are spaced out on the armature core. What is a coil span? The coil span is the distance between one conductor of a certain phase and the corresponding return conductor. The pole pitch is defined as the distance between two consecutive poles. M. Armature Currents and MMF of 5-Phase Machine The armature currents of 5-phase machine can be expressed with formula (1). Here, e = E 1 = E 2 = E. 0. However in practise this often isn’t the best choise because of the high harmonic content. • Pitch of a Winding (Y) In general, it may be defined as the distance round the armature between. A pole pitch in an electrical machine is equal to 180° electrical. 57. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. This advancement is measured in terms of armature conductors and is called back pitch. The alternator has 18 slots per pole and the first coil lies in slots 1 and 16. m. There are 0. 951, 0. Each phase in this case consists of four coils (two per slot). Lap and Wave winding are explained. Coil span is 16 – 1 = 15 slots. The two sides of a coil are placed in two slots on the stator surface. Identify number of rotor slots, number conductors / slot, coil span, number of slots per pole. Download Solution PDF. AC compound generator usually has lower resistance. . Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. For a simplex lap winding, the commutator pitch YC = 1 and coil span YS ~ pole pitch. Calculate the emf generated in each phase when the machine runs at 375 rpmHence, pitch factor or coil span factor K p = Cos(/2). The term “winding pitch” refers to the ratio of the number of winding slots enclosed by each coil in the alternator stator to the number of winding slots per generator pole. In such coils, the two coil sides are not under the poles. 15 Consider the armature conductor marked X in Fig 1. 5. When measured in electrical degrees one pole itch is equal to 1800. In general, electrical degrees equals mechanical degrees times 1/2 the number of poles. At this situation, two opposite sides of the coil lie under two opposite poles. Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. ( c) 96 stator slots, six-poles, coil spans 1 to 13. Emf induced per coil side is E. For making coil span equal to a pole pitch in the armature winding of a dc generator, the back pitch of the winding must equal the number of. No matter how many poles, each pole always spans exactly 180 electrical degrees, and it is called pole pitch. Zoom In Zoom Out Reset image size. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. L = πD/p = πD/ = 43 x 24 = 1048 ( satisfactory) Ex. The Separation between the top and bottom sides of a coil is known as back pitch and is represented by (Y b). Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding. The value of α will usually be given in the question, if not, then assume kc = 1. A 144-slot stator has a whole coiled 12-pole three-phase winding. . Now labeling the starting end of each coil is easy,. This number is known as coil span. 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 coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below. It is usually measured in terms of teeth, slots or electrical degrees. Obtain a full-pitch winding. Here, e = E 1 = E 2 = E. See solution. 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. 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. 60o groups, 2-layer winding is used. View full document. The coil span or coil pitch for short or fractional pitch coil is less than 180 electrical degrees. Share on Whatsapp Latest UPSC IES Updates. 0. To understand, it simply means that one parallel path is in N-Pole and another parallel path in S-pole. Supposing that each coil under the pole pitch has. m. 160 degrees b. 1: How to get flux, based on the rotor, through a coilspan coil (the coil span is closest to pole pitch, 3. by 20o to full pitch distance. Calculation: Given that,For making coil span equal to a pole pitch in the armature winding of a d. In general, if the coil span falls short of full-pitch by an angle α (electrical)*, then kc = cos α/2. You can investigate three-phase integer-slot, fractional-slot and concentrated windings, both with single and double winding layers where appropriate. 24 where polepitch of 4 has been assumed), then winding is called full-pitched. Pole pitch = 180 electrical degrees = S/P = 2C/P. Back pitch (Y b): It is the span of the coil from the back end. 1 times the pole arc. 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. in the two coil sides. poles, 18 slots alternator, the pole pitch is n = 18/2 = 9 slots. Coil Span (ii) Resultant 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. The coil-span is 144° (electrical). In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch, back pitch, pole pitch, coil pitch, etc. ; Here, e = E 1 = E 2 = E. The coil span is 150°. 7 slots c. The distance between the two sides of a coil is called the coil. fs. The usefulness of winding distribution and chording in reducing or eliminating harmonics will be touched on in. situation, two opposite sides of the coil lie under two opposite poles. To get a coil around every tooth, we need two winding layers (double layer winding). Looking at the diagram in the question. Show transcribed image text There are 3 steps to solve this one. 10. Corresponds to 180/12 i. 14. 7. To calculate the pitch factor, we need to consider the pole number and the fractional pitch. (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. pole pitch = 180 electrical degrees or π electrical radians. f. The pole arc should be about 70% of pole pitch and length of core about 1. The. the coil will be in 180o. The flux per pole is 0. 86. slots. 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 ). If the coil span of a single coil is less than the pole pitch of 180° electrical, i. , coil span is 180º electrical) is called a full-pitch coil. The coil-span chosen is less than the full-pitch because of the inherent advantages of chording. Then the coil span value is _____. ; Coil Span: It is the angular distance between the two sides of the coil. 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. (16) k p1 = sin β 2 <1 where β is the coil span in °electrical, β=sα; s is the coil span in slots. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. 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. m. Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding. Hence, during rotation when one side of the coil comes under north pole, the other side of the coil comes under south pole. 96 stator slots, 6poles, coil span 1to 12. per slots, in a double layer. They are two basic physical types for the windings. e. Distribute the winding uniformly under different poles d. of slots per pole = 2 = 6 saree tensed gOSeaee Slot pitch, a = oF slow/pole > No. – Comparator. In such coils, the two coil sides are not under the poles. So if coil span is ‘n’ slots or 180° electrical the coil is called 180° full pitch coil. Problem. Author: Frank D. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. 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. 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). Hence emf induced in one side of. Transcribed Image Text: (d) obtain a full-pitch winding. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 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. In a 4 pole, 35 slot dc armature, calculate the coil span a. See answer (1) Best Answer. Pole pitch is always equal to 180o. . arrow_forward. coil pitch in terms of slots4. Coil–span or coil-pitch. situation, two opposite sides of the coil lie under two opposite poles. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. It means that coil span is 180 electrical degrees. ( ) () ⎪ ⎪ ⎪ ⎩ ⎪⎪ ⎪ ⎨ ⎧ = − = − = − = − = sin 8 /5 sin 6 /5 sin. Sanfoundry Certification Contest of the Month is Live. A: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. e. a. , 5 slot‐pitches in Figure 2a) [8, 9]. . Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . it is said to the a fractional-pitch coil. 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. Download Solution PDF. In a fractional pitch winding, the coil span is made less than 180 degrees electrical space. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. 956, 0,647 02A pole pitch covers 25/4 = 6. The pole pitch is 10 slots, and the coil pitch is 9 slots. We will start Red at slot 1. 86 O 119. p. 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. It is also called a chorded coil. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. 24 B where coil pitch is 3/4th of the pole pitch), then the D. Full pitch winding. 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. 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. Short-pitched coils are deliberately used because of the following advantages: 1. The distance between the two sides of an individual coil of and AC armature winding id termed the coil pitch. 8. 31. Pole and slot numbers. 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. Coil span or Coil Pitch. Transcribed Image Text: (d) obtain a full-pitch winding. Calculate the sinusoidally distributed flux per pole required to give a line voltage of 11 kV on open circuit, and the full. 2 sin 70 wb/m? where O is angle measured from neutral axis. 14. ( 2) The harmonic voltages decrease in a short pitch coil, thereby improving the waveform of the induced voltage in the winding. 2 sin 30+0. Calculate the distribu factor for a 36-slot. 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. 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. 339 IC function as. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. Por a full-pitch coil, Kr = I (unity) r:or a fractional-pitch coil, Kr < 1 6. Author: Frank D. 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. 14. g. Assume a coil span of unity. fs. M. Expert Solution. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. Coil Span: The number of core slots spanned by the sides of the coil. The formula for pitch factor is given by The pitch factor in the above equation is for fundamental component of emf. In SWAT-EM we can set the coil span explicite. Where n is the nth harmonic. 12 Wb and a 20% 3 rd harmonics. Table 1 lists suitable combinations of stator slots and rotor poles for six-phase windings and gives the corresponding number of slots per pole per phase q6~. 4 pole = 90o. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. of slots / slots per pole. (a) multiplex (b) fractional-pitch (c) full-pitch (d) pole-pitch 3. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. 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. Calculate the pitch factor for an alternator winding with 36 slots, 4 poles, and coil span of 1 to 8. It. . Coil span and commutato pitch b. fs. 0 D. Here ξ is the chorded angle or short pitch angle. Its magnetic poles can be salient (protruding or sticking out from the surface of the rotor), as shown in Fig. e. Place the arrows according to the slot pitch. ’s of consecutive turns c. e. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. f. 6. ; Here, e = E 1 = E 2 = E. This lecture will discuss;1. winding is fractional-pitched. It is one pole pitch. 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. ISBN: 9780073373843. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. 0 B. 5 ≤ q ≤ 3, are presented in Section 3. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. Its value is always less than unity. c. Short-pitched coils are deliberately used because of the following advantages: 1. (a)Find the total number of coil groups in the machine. . Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. 60 hz, 10-pole alternator has 120 slots and 4 turns in every coil. full, s. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. e. 958] (B) Determine the maximum flux per'pole when connected to a' 220-volt,60-cycle line, neglecting local resistance and reactance drops. arrow_forward A. The coil span of a full pitch coil is always 180° electrical. Calculate its coil span factor. The dc armature winding in which coil sides are a pole pitch apart is called ____ winding – Full- pitch. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. Coil span or coil pitch Ys: It is the distance between the two sides of a coil measured in terms of armature slots. Coil – span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. In this case, there is a phase difference between the e. 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. The back pitch and front pitch adopted could be respectively. Both, 7/9 and 8/9, are equally close to 5/6 but I would select 8/9 for better flux utilization. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. TERMS Coil Throw: The location in an armature core of the sides of a coil starting in slot number one (1). Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. If each coil is short pitched by an angle of 36 ∘ electrical. Calculation:A coil rotated in a magnetic field induces current. 6. arrow_forward. e. 6A. TYPES OF AC MACHINES WINDINGS. m. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. In other words, the distance between the two coil sides of a coil will be equal to the distance. Full Pitch and. A 3-phase, 4 pole, Y- connected alternator has 72 slots with two conductors per slot. Expert Solution. Generators 897 winding is fractional-pitched. Register to editPitch factor problem. e. 10 are one pole pitch or n slots or 180° electrical apart, the coil is called full pitch coil. Coil spanA: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. less than 180° electrical, the coils are called, short pitched coils or fractional pitched coils. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. 7. The pole pitch, S/P, is also fractional, so that the coil-span cannot be of full-pitch. Calculate the pitch and distribution factors for the fundamental, the third, and the fifth harmonics in the phase voltage. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. o5Wb. 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. View the full answer. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. , or 5/6 × 180° = 150 electrical degrees. This winding has 12 slots per pole per phase. Coil pitch: The distance measured in terms of armature slots or armature conductors between two sides of a coilQuiz # Solve the following problems. Prelude to Synchronous Generator Induced E. For n th harmonic. the core length 32 cm, and the stator coil span four fifth of the pole pitch. e. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 16 wb/pole and is distributed sinusoidally over the pole. The induced emf in each coil side. advertisement. • In double layer windings used in. 2 sin 50 +0.