It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. ) A 6-pole, 3-phase, 60-Hz alternator has 12 slots per pole and four conductors per slot. Coil Span: It is the angular distance between the two sides of the coil. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. B. 6. Calculate the armature winding distribution factor. If the generator is running at 1200 rpm, find the average voltage generated between brushes for wave winding. Pole pitch is always equal to 180o. 24 where pole- pitch of 4 has been assumed), then winding is called full-pitched. . (2) 𝑘 𝑐 𝑛 = c o s 𝑛 α 2. The pitch factor of an alternator is a measure of the winding distribution along the armature. three factors: the pitch factor (also called chording or coil-span factor), the distribution factor (also called breadth, spread or zone factor) and the skew factor. it is said to the a fractional-pitch coil. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. 086 Wb, what will be the values of the emfs? phase. EXAMPLE: Calculate the pitch factor for a alternator winding with 36 slots, 4. As the two coil sides are separated in space by an angle of (180-ε) i. The coil span is 150 electrical degrees. 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. In SWAT-EM we can set the coil span explicite. Duplex Lap Winding. The first coil lies in slots 1 and 16. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. You can compare the maximum fundamental winding factor for different. It is in fact the periphery of the armature spanned by the two sides of the coil. Explain the following armature winding terminologies (i)commutator Pitch (ii)Coil Side (iii)Pole Pitch. SEE MORE TEXTBOOKS. In a 10 pole, lap wound de armature, the number of active armature conductor per pole is 50. The armature winding is housed in 360 stors with 6 conductors per slot. 12. Pitch factor. Answer Coil span factor = 0. 36 stator slots, 4-pole, coil span 1to 8 ii. 0. Question: 2 Problem 2: The flux distribution curve of a smooth core 50HZ generator is B(0) = sin 8 +0. 165 degrees. Expert Solution. . ) A 6-pole, 3-phase, 60-Hz alternator has 12 slots per pole. Here, e = E 1 = E 2 = E. 05: B) 0. Then, the pitch factor will be equal. 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. Also note that the diagram gives no information about the coil-span or pitch; thus for example in the 36-slot case a full-pitch winding would have a coil-span of 9, but 8, 7 or 6 could also be used (all with 2 coil-sides per slot). 10 A three-phase, wye-connected alternator has 15 slots/pole. It may be the full pitched or short pitch. Pole pitch is always equal to 180o. 16. Coil Span: It is the angular distance between the two sides of the coil. in them are additive. It is generally denoted by K c and its value is always less than unity. The number of segments lying between the ends of the coil is known as the commutator pitch. , pole-pitch ) is known as 'Full Pitch'. It means that coil span is 180 electrical degrees. For a simplex lap winding, the commutator pitch YC = 1 and coil span YS ~ pole pitch. Calculation:The angular distance between the two coil sides is less than one pole pitch, it is termed short pitch or fractional pitch coil. View the full answer. SEE MORE TEXTBOOKS. The separation between the top and bottom sides of a coil is called Coil span. Coil–span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. Its flux per pole is 0. It is defined as the angular distance between the central line of one pole to the central line of the next pole. The flux per pole has a fundamental component of 0. 0. Winding table. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. c. (b) Determine the pitch (or coil span) factors for the following windings: i. Thus coil span of either 6 or 7 may be selected. = 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. e. Resultant flux in the air gap is 55 mWb per pole. ∴ e = E 1 + E 2 = 2E. Coil pitch: The distance measured in terms of armature slots or armature conductors between two sides of a coilQuiz # Solve the following problems. The current is in same direction in both the sides of the coil. of poles, P= 4 No, of slots = 24; No. e. , coil span is 180º electrical) is called a full-pitch coil. A 3-phase, 12-pole, star-connected alternator has 180 slots with 10conductors per slot and the conductors of each phase are connectedin series. 0 C. Solution for For alternator having fractional pitch of 11/12 the coil span is a. 6. You can read more. 0. The pole pitch is 35cm, the core length is 32cm & sta- 4th tor coil span is of pole pitch. The coil span of a full pitch coil is always 180° electrical. placed in the top layer of the slot & the other side of the coil is placed in the bottom layer of another slot nearly a pole pitch apart. This distance is measured in terms of armature slots or armature conductors that come between two adjacent pole centers. fs. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. 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. Result- ant flux in the air-gap is 5 ´ 10– 2 webers per pole sinusoidally distributed. . Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. 135 degrees d. Register to editPitch factor problem. The primary reason for making the coil span of a d. m. 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). where: coil. Back pitch (Y b): It is the span of the coil from the back end. 12Wb. Hence emf induced in one side of. 31. Pole pitch is the mechanical angle between adjacent poles, e. 10 are one pole pitch or n slots or 180° electrical apart, the coil is called full pitch coil. 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. Define Pitch Factor /Distribution Factor and present the formula to calculate. A 3-phase, 50 Hz, 2-pole, star connected turbo alternator has 54 slots with 4 conductor per slot. BUY. On the other hand, if its span is less than a pole-pitch. Looking at the diagram in the question. 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. Petruzella. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. If the coil pitch is less than one pole pitch, the coil is called the short-pitch coil or fractional-pitch coil. Short Pitch Coil. Share on Whatsapp Latest UPSC IES Updates. This lecture will discuss;1. 3. The distance between the two sides of an individual coil of and AC armature winding id termed the coil pitch. In all cases, the coil span should not differ too much from the pole pitch to ensure that when one coil side is under a north pole, the other coil side is under a south pole . • Key design factors include number of poles, number of slots, and number of slots spanned by coils. m. 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. e. fs. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . In a full pitch coil, the coil span will be 180° electrical (equal to pole pitch). slots. 125 Wb and a. If each coil is short pitched by an angle of 36 ∘ electrical. 4 pole = 90o. Prelude to Synchronous Generator Induced E. Discuss the effect of making the coil span very different from the pole pitch on (a) the coil emf and (b) the coil torque. in the two sides of the coil. 9 slots . There are 2,500,000 Maxwells entering the armature from each North Pole, and this flux is sinusoidally distributed along the air gap. A winding constituting a basic unit under a pole-pair (N and S) is repeated for any number of pole pairs when q is integral. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. c. The average pitch Y A = 2 B F Y Y +. 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. For 20 slots, 4 polesThe winding of a 4-pole alternator having 36 slots and coils and a coil span of 1 to 8. It may be the full pitched or short pitch. P˚ = Pitch = coil span in no. It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. If the coil span is less than the pole pitch (as in coil Fig. This winding has 12 slots per pole per phase. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2. 00 O…influence of slot/pole number (S/P) combinations on the rotor bar copper loss, a winding harmonic index is described in Section 2. 9780133923605. Hence, the pole pitch of that DC machine would be 24. 10. Here, e = E 1 = E 2 = E. It is lesser than the value in the first case. The part of the coil in which EMF is generated is known as _____. M. 1kv. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. F induced in the other side of the coil. MMF OF ARMATURE A. the flux per. Where n is the nth harmonic. 0 C. In this case, the coil sides lie under opposite poles, hence the induced e. The primary reason for making the coil span of a d. Pole pitch is always equal to 180o. 06 weber distributed sinusoidally over the pole. Coil Span: The number of core slots spanned by the sides of the coil. what is coil pitch or coil span. 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 4 pole, 12 slot lap wound dc armature has two coil side per slot. Determine the pitch (or coil span) factors for the winding , 96 Stator slots ,4 poles, coil span 1 to 18 13. A) 1. m. it is defined as the peripheral distance between the center of two adjacent poles in a DC machine. 10 slots d. 16 wb/pole and is distributed sinusoidally over the pole. 24 where polepitch of 4 has been assumed), then winding is called full-pitched. Here’s the best way to solve it. 0. The coils are made up of 8 turns, and the windings are double layer. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. Winding pitch is the coil span divided by the pole pitch, e. If the angular distances between the two coil sides are less than one pole pitch, it is termed short pitch or fractional pitch coil. When the coil is having a span of less than 180° electrical, it is known as a short-pitch coil. F = 0. 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. 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. Transcribed Image Text: (d) obtain a full-pitch winding. 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. Commutator pitch Y C = ±1. 0 i D. 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. 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. The arithmetic sum of induced emfs is 2E. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2 coil sides per slot. If the machine gives 3300 V between lines on open circuit with sinusoidal flux distribution. 2. pole pitch = 180 electrical degrees or π electrical radians. fs. 1993) Example 37. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. A 10 MVA, I KV, 50 Hz, 3-phase, star-connected synchronous seberatur is driven ur 300 r. Step by step Solved in 2. 1. 60o / 90o = 2/3. No matter. 5 c) 18 d) 6 View Answer. c. (a) multiplex (b) fractional-pitch (c) full-pitch (d) pole-pitch 3. by 20o to full pitch distance. A pole pitch is always 180° electrical regardless of the number of poles on the machine. Full pitch winding. A 4 pole AC machine has its winding housed in 48 slots with coils of span 11/12 th of a pole. 1, if the coil sides are placed in slots 1 and 7, then it is full-pitched. In general, electrical degrees equals mechanical degrees times 1/2 the number of poles. Short-pitched coils are deliberately used because of the following advantages: 1. Zoom In Zoom Out Reset image size. 951, 0. A 3 phase 1800 kVA, 3 kV, 50 Hz, 250 rpm, salient pole. Generators 897. TERMS Coil Throw: The location in an armature core of the sides of a coil starting in slot number one (1). (2006), “Distribution, coil-span and winding factors for PM. Hence, the total e. Pole pitch. If we used short pitched winding for armature winding than pitched factor is included in EMF equation in Alternator. Full pitched coils have the advantage of giving maximum emf induced in the coil. Since one pole presents 180 electrical space degrees so the slots pitch. of slots / slots per pole. 15. 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 commutation is improved in short-pitched coil, but the emf induced will be less compared to full-pitch. Here we have a 4-pole alternator with a 48 slot stator. slots. 9 and the efficiency is 0. of slots per pole = 15 but coil span is… Q: A synchronous generator has 9 slots per pole. You can read more about Full Pitch and Short Pitch Winding at:. 911 V B. the coils cannot be full - pitched; they may be short - pitched with 15 slots, or long - pitched with 16 slots. 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. If the coil span is equal to the Pole pitch then it is called a full pitch coil. 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. Q: Explain the following Armature Winding Terminologies (i) Coil Span (ii) Resultant Pitch A: In the following section, coil span and resultant pitch related to armature winding technology has… Q: Assume that a four-pole de machine has an armature with a radius of 15 cm and an effective length of…In the second example, with a pole pitch of 15. A. o. In a short pitch coil, the coil span will be (180 -. Two-and four-pole rotors have normally nonsalient poles, while rotors with more than four poles have salient poles. m. 956 1. 8. α = Angle of short pitch = 20o. Pole – pitch. The maximum pole flux is 8. Supposing that each coil under the pole pitch has. 12 Wb and a 20% 3 rd harmonics. 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. What is a coil span? The coil span is the distance between one conductor of a certain phase and the corresponding return conductor. The resultant coil voltage $𝐸_{𝐶}$ is equal to the phasor sum of $𝐸_{𝐶1}$ and $𝐸_{𝐶2}$. 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. BUY. Coil Span (ii) Resultant Pitch. Assuming single turn coil, calculate the back pitch for progressive and retrogressive winding. ∙ 10y ago. 3 mWb and the total number of armature conductors is 1000. Problem. I need answer within 20 minutes please please with my best wishes. In the considered motor, the fundamental winding factor is equal to the skew factor due to unity fundamental coil-span and distribution factors. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. 966 and 0. 6. It is also called a chorded coil. 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. 57 O 127. The coil span of a full pitch coil is always 180° electrical. This lecture will discuss;1. Obtain a coil span of 180 degrees (electrical) b. 25 O 5. At this situation, two opposite sides of the coil lie under two opposite poles. Distribute the winding uniformly under different poles d. 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. Alternatively, this type of coil is also called a short-pitch or chorded coil. The pitch of the coils is 2 slots less than the pole pitch. Step by step Solved in 4. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched coil. Three kinds of coil spans are used, they are 4-solt pitch, 3-solt pitch, and 2-solt pitch. ed = electrical degree Example 2: Calculate the pole pitch for a three phase 4 pole ac machine having 36 stator slots. The pitch of the coil is 2 slot less than the pole pitch. In other words, the distance between the two coil sides of a coil will be equal to the distance. . It may be the full pitched or short pitch. N st 2p r; 12 14 16 18 20 22; 12:. m. This answer is:Full-pitch windings have a coil pitch of 1, which means the coil span is equal to the pole pitch. The. 163Wb. Pole arc/ pole pitch = core length/ pole pitch = 0. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Each of these coil spans is five slots, so this choice of winding. Problem 1 : Develop the layout of a lap winding for a 3 phase ac machine having 4 pole and 24 slots. 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. a. The distance between the two sides of a coil is called the coil. , Y = 2/3 τ p. The flux per pole has a fundamental component of 0. A coil whose sides are separated by one pole pitch (i. e. Because a chording more than 1/3 pole pitch would noticeably reduce the phase emf. Calculared the flux per pole required to give Il kV line voltage on open circuit voltage. Electricity for Refrigeration, Heating, and Air Conditioning (MindTap Course List). 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. e. arrow_forward A. 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). 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 ____________. Coil span or Coil Pitch. g. K p = cos (nα/2) Where n is the nth harmonic. A coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below: A coil having a span less than 180⁰ electrical is called a short pitch coil or fractional pitch coil. g. A: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. A pole pitch is always 180° electrical regardless of the number of poles on the machine. 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. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. EE - 422 DC & AC MACHINERY 2nd Semester AY 2020-2021 ENGR. armature winding equal to a pole pitch is to (a) obtain a coil span of 180° (electrical) (b) ensure the addition of e. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. Obtain a coil span of 180 degrees (electrical) b. e. Then, the pitch factor will be equal. Fractional slot winding 6. Result Number of. ( 2) The harmonic voltages decrease in a short pitch coil, thereby improving the waveform of the induced voltage in the winding. The winding is 5/6 pitch. 0 D. Corresponds to 180/12 i. Answer: 0. 339 IC function as. b) 96 stator slots, 6 pole, coil span 1 to…. 0. 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. 363Wb and a 15% third harmonic. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. Let E 1, E 2 and E R be the emf induced in coil side lying under North Pole, South Pole and resultant of emf generated in both the active lengths of coil. m. 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. 1 is connected to coil side in slot No. 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. Give the values of front pitch, back-pitch and commutator pitch. Hence, the pitch factor or the coil span factor for the n th harmonic is given by, kcn = cos nα 2. In this case, the coil sides lie under opposite poles, hence the induced e. Calculate the rms value of the induced emf per phase of a 10-pole, 3-φ, 50-Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. g. It means that coil span is 180 electrical degrees. Find the terminal voltageon open circuit. First, a double-layer winding is investigated with the number of slots Q, pole pairs p and a constant coil pitch . Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. The usefulness of winding distribution and chording in reducing or eliminating harmonics will be touched on in. For a coil span of 13/15 of a pole pitch, the phase winding factor is: K_p = cos(π * 13 / (2 * 15)) = 0. A=2, B=1 and C=2 and D=5. M. Author: Robert L. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. When a coil is having a span of 180° electrical, it is called a full-pitch coil. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a. 12. It may be the full pitched or short pitch. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. 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. The induced emf in each coil side. Determine the phase andline values of emf if the machine runs at 600 rpm and the flux per poleis 0. of consecutive turns (c) distribute the winding uniformly under different poles (d) obtain a full-pitch winding. arrow_forward. F induced in one side of the coil will be in 180˚ phase shift with E. Lap and Wave winding. In this case, we have a 10 pole alternator with coils wound in a fractional pitch of 18/21. However, the phase winding factor for short-pitched coils is different from that of full-pitch coils. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. Coil Span Factor - Coil Span Factor is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them.