advertisement. The term "region" is important, because a design with 3 slots per pole and phase, for instance, can only be pitched 6/9 or 7/9 or 8/9. 025 Wb entering the armature from each north pole, and this flux is sinusoidally distributed along the air gap. 12 Wb and a. 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. Each phase in this case consists of four coils (two per slot). At this situation, two opposite sides of the coil lie under two opposite poles. In such coils, the two coil sides are not under the poles. Petruzella. 31. Better emf waveform in case of generators 6. 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. Pitch Factor or Coil Span Factor is defined as the ratio of EMF generated in the short-pitch coil to the EMF generated in the Whefull-pitch coil. may or may not be exactly equal to pole pitch B. • To view the coil sides / coils, we must look below from above the slots as depicted in figure. In a 4-pole, 35 slot dc armature, 180 electrical degree coil span will be obtained when coils occupy _____ slots. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. The coil span is 160°. Show transcribed image text There are 3 steps to solve this one. Zoom In Zoom Out Reset image size. Identify number of rotor slots, number conductors / slot, coil span, number of slots per pole. 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 case of short-pitch coil, the voltages generated in each coil side are not in phase. 24 B where coil pitch is 3/4th of the pole pitch), then the D. It is equal to the number difference of the conductor connected to a given segment of the commutator. Since this machine has 8 poles and a pole-pitch of 48/8 = 6 slots, the coil pitch here is 5/6 = 0·833 p. 1. 0. The reduction fraction is the pitch factor. 0 C. The width of the coils is 5/6 of the pole pitch. Calculate the emf generated in each phase when the machine runs at 375 rpm Hey Aspirants. 05 Wb, sinusoidally distributed. 2. A 3-phase, 50 Hz, 2-pole, star connected turbo alternator has 54 slots with 4 conductor per slot. The coil span equal to 180 electrical degrees: The coil span is less than 180 electrical degrees. Solution for For alternator having fractional pitch winding of 10/14 the coil span is 4. it is defined as the peripheral distance between the center of two adjacent poles in a DC machine. When 40V DC voltage is applied to a single-phase AC motor, it draws 1A current. $$\mathrm{Slot\:per\:pole =\frac{90}{6}= 15}$$ For a full-pitch coil, the coil span is 15 slots. #Alternator #Protectionofalternator#elect. ( b) 42 stator slots, four-poles, coil spans 1 to 10. If the coil span is less then one pole pitch than it is called short pitch coil. When measured in electrical degrees one pole itch is equal to 1800. Each phase in this case consists of four coils (two per slot). e. The winding distribution factor of the alternator is. Determine the phase and line voltages if the coil is full pitched. Winding table. If the coil span is equal to the Pole pitch then it is called a full pitch coil. armature winding equal to a pole pitch is to (a) obtain a coil span of 180° (electrical) (b) ensure the addition of e. In a 4-pole, 35 slot dc armature, 180 electrical degree coil span will be obtained when coils occupy _____ slots. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. The pole pitch is defined as the distance between two consecutive poles. In the considered motor, the fundamental winding factor is equal to the skew factor due to unity fundamental coil-span and distribution factors. For n th harmonic. winding is fractional-pitched. 2 Winding design with star of slots The star of slots is a collection of phasors which illustrates allIf 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. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. IV. Author: Frank D. Pole pitch is defined as the angular distance between the central line of one pole to the central line of the next pole. Transcribed Image Text: (d) obtain a full-pitch winding. Publisher: McGraw-Hill Education. This chapter covers the calculation of winding factors and armature MMFs, harmonic analysis of armature MMFs. Pole pitch is the electrical angle between the north pole and. 2 sin 70 wb/m? where O is angle measured from neutral axis. Problem 1 : Develop the layout of a lap winding for a 3 phase ac machine having 4 pole and 24 slots. 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. When the coil is having a span of less than 180° electrical, it is known as a short-pitch coil. The current is in same direction in both the sides of the coil. Q: For alternator having fractional pitch winding of 8/14 the coil span is 102. m. machines with. The coils are place in 60 uniformly distributed slots around the inner perimeter of the stator. (c)Find the number of coils in a coil group, m. Pole pitch is the peripheral distance between two adjacent poles. If the coil span is equal to the Pole pitch then it is called a full pitch coil. This lecture will discuss;1. 086 Wb, what will be the values of the emfs? phase. Both Y B and Y F should be nearly equal to a pole pitch. Pole pitch = 180 electrical degrees = S/P = 2C/P. g. • Key design factors include number of poles, number of slots, and number of slots spanned by coils. 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). L = πD/p = πD/ = 43 x 24 = 1048 ( satisfactory) Ex. Resultant flux in the air gap is 55 mWb per pole. , a pitch, or an pitch, etc. , Y = 2/3 τ p. The coil is also short-pitched (eg spam of two sides of. 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. D 2 L = Q / C 0 ns = 500/( 153 x 8) = 0 m 3 Using round poles for the salient pole alternator and assuming ratio of pole arc to pole pitch as 0 and pole arc equal to core length. 10 A three-phase, wye-connected alternator has 15 slots/pole. per Phase: Part 1In this video, I'll give you an idea how to derive the fundamental pitch factor (coil span f. The value of α will usually be given in the question, if not, then assume kc = 1. the flux per. 125 Wb and a 25% third component. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. 5. (8) A SIMPLE explanation of Full Pitch and Short Pitch Winding. Machine, Nagpur Univ. The skew factor reflects the flux reduction if the winding is angularly twisted along the axis. Transcribed Image Text: 9. (ii) Pole pitch: The over hang portion of the coils depend upon the coil. Assume a coil span of unity. 7. pdf from CSE 302 at World University of Bangladesh. number of slots and a coil span of two slots require at least 18 slots. g. If the coil span is less then one pole pitch than it is called short pitch coil. Author: Frank D. For example, the 24‐slot/10‐pole PM machine in Figure 1a can be derived from two 12‐slot/10‐pole PM machines with the stator shift of 75 mechanical degrees (i. Generally. 7 slots c. 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. it is defined as the peripheral distance between the center of two adjacent poles in a DC machine. Study now. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. Calculate the sinusoidally distributed flux per pole required to give a line voltage of 11 kV on open circuit, and the full. Here we have a 4-pole alternator with a 48 slot stator. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. 135 degrees d. 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. Coil–span or coil. It is usually measured in terms of teeth, slots or electrical degrees. Calculate the emf generated in each phase when the machine runs at 375 rpmHey Aspirants. When two capacitors of reactances 10ohms and 20 ohms are connected in parallel across a 100 V supply, total VAR drawn will be _. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. Then, the pitch factor will be equal. It is one pole pitch. , coil span is 180º electrical) is called a full-pitch coil. SEE MORE TEXTBOOKS. 80The coil pitch of such distributed windings is normally at least three slots which brings about a high winding resistance and occupies much space for the end windings. This answer is:Full-pitch windings have a coil pitch of 1, which means the coil span is equal to the pole pitch. The flux per pole has a fundamental component of 0. The fundamental pitch. 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. Emf induced per coil side is E. 2 sin 50 +0. 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. F. 1993) Example 37. Expert Solution. α = Angle of short pitch = 20o. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. When a coil is having a span of 180° electrical, it is called a full-pitch coil. The coil span is 150°. 24 where pole- pitch of 4 has been assumed), then winding is called full-pitched. arrow_forward. Most windings have < . What is the flux per pole if the voltage on open circuit is 1. 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 ). It. Key. (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. ’s of consecutive turns c. g. fs. 33 percent of pole pitch to obtain the maximum reduction of harmonics. 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. 85 lagging. To improve the wave form only 80% of the pole pitch is wound. Answer: c Explanation: Pole pitch is called as center to center distance between two adjacent poles. ( b) 42 stator slots, four-poles, coil. In this case, we have a 10 pole alternator with coils wound in a fractional pitch of 18/21. Figure 4 shows the flux distribution linked to a short-pitch coil. Now labeling the starting end of each coil is easy,. Short-pitched coils are deliberately used because of the following advantages: 1. It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. Coil–span or coil-pitch. Understand what Full Pitch and Short Pitch Windings are, and what Coil Span is. ); and k y is the short pitch factor. e. In a 4 pole, 3 phase alternator, armature has 36 slots. m. The winding is 5/6 pitch. Required: a. Expert Solution. The coil used in double layer winding are diamond shaped as in the dc windings. First. It. 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. Front connections 8+7=15; 30+7-30=7 8. Pole Pitch, Coil Span, Back Pitch, Front Pitch, Commutator Pitch in Armature Winding of DC Machines are explained in this video. See moreIf the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. The armature windings conduct AC even on DC machines, due to the commutator action (which. This type of winding is mainly used for. m. Y-connected alternator has 9 slots per pole and a full-pitch. It is always less than unity. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched coil. 7. Coil spanA: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. 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. Distribute the winding uniformly under different poles d. You can read more. However, the phase winding factor for short-pitched coils is different from that of full-pitch coils. 160 degrees b. Back pitch (Y b): It is the span of the coil from the back end. If the maximum flux per pole, with a sinusoidal distribution, 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. Coil span or Coil Pitch. a. The coil-span chosen is of course less than the full-pitch. 1 and No. The slots per pole per phase are 8 and the coil span is 20 slots. m. A 10 MVA, I KV, 50 Hz, 3-phase, star-connected synchronous seberatur is driven ur 300 r. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. e. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. 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/. ; Coil Span: It is the angular distance between the two sides of the coil. Where n is the nth harmonic. Compared to the overlapping winding above we need only 3 slots for the two poles. 1: How to get flux, based on the rotor, through a coilspan coil (the coil span is closest to pole pitch, 3. 12Wb and a third harmonic component. . 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. g. I need answer within 20 minutes please please with my best wishes. kp: 0. D. Calculate its coil span factor. 1822 V C. K pn = cos nα/2. Full Pitch and. 6. 4 Winding Factor Both distribution factor (Kd) and pitch factor Kp together is known as winding factor Kw. Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. 6 turns. Coil Span: It is the angular distance between the two sides of the coil. 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. 2 Selecting the coil span for a given pole pitch. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. the core length 32 cm, and the stator coil span four fifth of the pole pitch. When the parallel path is twice the number of poles then it is known as Duplex Lap Winding. The separation between the top and bottom sides of a coil is called Coil span. EXAMPLE: Calculate the pitch factor for a alternator winding with 36 slots, 4. 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. Here, the 1This means, if E 1 and E 10 are the emf induced in respective coil sides then the total emf induced will be E 1 +E 10. Boylestad. In a 4-pole, 35 slot d. The pole pitch is 35 cm. The distance between the two sides of a coil is called the coil. The. 1. 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~. Here ξ is the chorded angle or short pitch angle. 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. 🔥engineers platform App Link. 163Wb. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. Determine the coil and commutator pitches for a 72-slot 288-segment six-pole frog-leg armature winding. Theta (electrical)=p/2 (theta (mechanical)) What is the formula for electrical angle. 5. A 4-pole, 50 Hz alternator has double layer winding with 10 turns per coil and number of slots are 60. Calculation:The angular distance between the two coil sides is less than one pole pitch, it is termed short pitch or fractional pitch coil. A 4 pole, 12 slot lap wound dc armature has two coil side/slot. Obtain a coil span of 180 degrees (electrical) b. . It is defined as the angular distance between the central line of one pole to the central line of the next pole. 25 O 5. A: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. 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. The total flux per pole is 10⁶ lines. m. Chording: with coil-span less than pole pitch 5. The coil pitch is short by 2 slots. 911 V B. If the coil span is. 150 degrees c. Fractional slot winding 6. 24, and assume first a short-pitched coil spanning half a pole pitch, then a long-pitched coil spanning one and a half. Determine the useful flux per pole. Note. 79. If the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. Assuming double turn coil, Calculate the back pitch for progressive and retrogressive winding. Here, e = E 1 = E 2 = E. If the coil span is equal to the Pole pitch then it is called a full pitch coil. If the span of the coil is reduced by an angle 'α' of electrical, then the. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. 36 stator slots, 4-pole, coil span 1to 8 ii. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch. Commutator pitch. 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. For example, in a 4-pole generator with a 48-slot stator (12 slots per pole), if each coil in the stator winding spans 12 slots then the ratio is 1/1 and the winding is full pitch. 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. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. C. However, the phase winding factor for short-pitched coils is different from that of full-pitch coils. Calculation:When the coil sides forming a coil are spaced exactly one pole pitch a part they are said to be of full-pitch. spanning over 180° (electrical). The phase spread is 60° and the flux per pole is 25-8 x 10 weber. 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. Since the winding is full pitched coil, so the pitch of each. (Elect. Full pitched coils have the advantage of giving maximum emf induced in the coil. 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. It is expressed in terms of electrical space degree. 85 lagging. 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. situation, two opposite sides of the coil lie under two opposite poles. In a full pitch coil, the coil span will be 180° electrical (equal to pole pitch). 11. For 20 slots, 4 polesThe winding of a 4-pole alternator having 36 slots and coils and a coil span of 1 to 8. of a 10-pole three-phase 50Hz alternator with 2 slots per pole per phase and 4 conductors. If the machine gives 3300 V between lines on open circuit sinusoidal flux distribution, determine. The primary reason for making the coil span of a d. Pole pitch. This is naturally equal to the total number of armature slots divided by the number of poles in the machine. 9 and the efficiency is 0. f. You can investigate three-phase integer-slot, fractional-slot and concentrated windings, both with single and double winding layers where appropriate. If fractional pitch is used, the emfs in the two coil sides are out of phase, which reduces the emf. (BTL-1) 4. Not ( I want a solution within 20 minutes because it is very urgent ) Q3//The armature of a 6600 volt, three-phase, 20-pole, 300 rpm star-connected alternator has 180 slots. 25 = 6 and 1/4 slots. 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. It is usually measured in terms of teeth, slots or electrical degrees. Here we can define one more term related to a coil called coil span. Pole pitch = S/P. e. 0. 15. Find the EMF produced by a DC generator connected to a 6 poles coil rotating at 1200 RPM. Calculate the armature winding distribution factor. The harmonic reduction in the voltage waveform of concentrated winding axial field PM machines is the subject of interest for many researchers. The pitch factor, in rotating electrical machinery, is. [Answer: 0. In this case, there is a phase difference between the e. If the coil pitch is shortened by 1/n of the pole pitch then the nth harmonic will be suppressed or the harmonics near to n will be with low voltage, because of the. Coilspan or coil-pitch. The primary reason for making the coil span of a d. Here, e = E 1 = E 2 = E. 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. of slots / slots per pole. (a)Find the total number of coil groups in the machine. 0. Calculate the pitch factor for: (i) Fundamental (ii) 3 rd harmonic (iii. 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. Coil pitch or coil span is defined as the angular distance between the two coil sides of one coil. In an alternator, for a coil having a span of 2/3 of pole pitch,. View the full answer. 1 the coil span should be approximately equal to a pole pitch. When the coil span is less than pole pitch (180 deg electrical), the winding is called short pitched or chorded. 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. Generators 897 winding is fractional-pitched. The meaning of FULL-PITCH WINDING is the winding of an armature in which the two sides of the armature coil span a distance equal to the pole pitch. 14. The skew factor reflects the flux reduction if the winding is angularly twisted along the axis. If the coil-span (or coil-pitch) is equal to the pole-pitch, then the coil is termed a full-pitch coil. It is usually measured in terms of teeth, slots or electrical degrees. For n th harmonic. of consecutive turns (c) distribute the winding uniformly under different poles (d) obtain a full-pitch winding. 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. Share on Whatsapp India’s #1 Learning Platform Start Complete Exam Preparation Daily Live MasterClasses. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. 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. 26. 6A. m. 4. 2 sin 30+0. (A) Determine the pitch and distribution factors. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. If the coil-span (or coil-pitch) is equal to the pole-pitch, then the coil is termed a full-pitch coil. Result- ant flux in the air-gap is 5 ´ 10– 2 webers per pole sinusoidally distributed. Por a full-pitch coil, Kr = I (unity) r:or a fractional-pitch coil, Kr < 1 6. Back Pitch. b) 96 stator slots, 6 pole, coil span 1 to…. . Pole Pitch: It is the angular distance between the two adjacent poles. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. 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. No matter. 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. #10 A 4-pole,3-phase, y-connected induction motor has 48 stator slots 8 series conductors per slot and coil pitch of 83. The armature coils are all connected in series. The spacing is expressed in terms of number of slots between the sides. 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. pole pitch5. frame. A 6-pole, 3-phase, 60 cycle alternator has 12 slots per pole and four conductors per slot. If the coil span is less than the pole pitch (as in coil Fig. It is always less than unity. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. The coil span or coil pitch for short or fractional pitch coil is less than 180 electrical degree. As against this if coils are used in such a way that coil span is slightly less than a pole pitch i. A chording angle ε is defined as the angle by which coil span departs from _____ a) 90° electrical space degrees b) 180° electrical space degrees c) 360° electrical space degreesSolution: No. β = 180o/ = 20o. A 3 phase 1800 kVA, 3 kV, 50 Hz, 250 rpm, salient pole. 1. There are 0. It is always 180° electrical.