6. This winding has 12 slots per pole per phase. 0. Now labeling the starting end of each coil is easy,. 31. Solution : n = Slots/pole = 36/4 = 9. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. c. 1NP2. . of consecutive turns (c) distribute the winding uniformly under different poles (d) obtain a full-pitch winding. Determine both the winding factor and the effective turns per phase. 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. In practice, coil pitch (or Span) as low as eight-tenths of a Pole Pitch, is employed without much serious reduction in emf. (2) 𝑘 𝑐 𝑛 = c o s 𝑛 α 2. This distance is measured in terms of armature slots or armature conductors that come between two. . (ii) Pole pitch: The over hang portion of the coils depend upon the coil. In this case, there is a phase difference between the e. In a fractional pitch winding, the coil span is made less than 180 degrees electrical space. 6. e. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. A 3 phase 1800 kVA, 3 kV, 50 Hz, 250 rpm, salient pole. 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. Calculation: Given that, Number of coils = 16Q2: 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. , pole-pitch ) is known as '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. Distribution factor (K d): The ratio of induced emf in the coil group when the winding is distributed in number of. The flux per pole is 80 m Wb and the coil span is 160° electrical. Coil span or coil pitch Ys: It is the distance between the two sides of a coil measured in terms of armature slots. It is usually measured in terms of teeth, slots or electrical degrees. 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. 85 lagging. 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. Calculate the emf generated in each phase when the machine runs at 375 rpmHey Aspirants. F induced in the other side of the coil. Its value is always less than unity. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. The coil span is five-sixth of a pole pitch. Allow 10 ampere for the field current and assume a voltage drop of 4 volts for the armature circuit. arrow_forward. b) 96 stator slots, 6 pole, coil span 1 to…. I need answer within 20 minutes please please with my best wishes. What is the pitch factor if a six-pole, three-phase alternator has 72 slots and a coil span of 1 to 10? Solution: 72 slots 6 poles = 12 slots pole k P = sin θ P 2 = sin (10-1) 12 × 180 ° 2 = 0. The random wire placement leads to a wider distribution of resulting wire length on the coil body and consequently a wider range of electric coil resistances. ISBN: 9780073373843. SEE MORE TEXTBOOKS. 16. Since one pole presents 180 electrical space degrees so the slots pitch. 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. 956 1. Pole pitch is the peripheral distance between two adjacent poles. 33 percent of pole pitch to obtain the maximum reduction of harmonics. Table of Contents Terms used in the armature winding Conductor Turn Coil Coil Side Front end and Back end connector Pole Pitch Coil Pitch or Coil span Pitch of a winding or winding pitch Back Pitch Front Pitch Resultant Pitch Commutator Pitch Calculation of pitch values Terms used in the armature winding TERMS Coil Throw: The location in an armature core of the sides of a coil starting in slot number one (1). In an alternator, for a coil having a span of 2/3 of pole pitch,. K pn = cos nα/2. The coil span of the alternator is 1 to 8. Study now. 0. Design a suitable double-layer lap winding for a 6-pole armature with 18 slots and two coil-sides per slot. may or may not be exactly equal to pole pitch B. Calculate the rms value of the induced emf/phase of a 10 pole, 3 , 50 Hz alternator with and in 2 layers. They save copper of end connections. Looking at the diagram in the question. Its flux per pole is 0. Because a chording more than 1/3 pole pitch would noticeably reduce the phase emf. The winding distribution factor of the alternator is. The coil-span chosen is less than the full-pitch because of the inherent advantages of chording. frame. Short Pitch Coil. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. Y-connected alternator has 9 slots per pole and a full-pitch. 924 359. The skew by one slot pitch gives the value of fundamental skew factor of 0. The commutation is improved in short-pitched coil, but the emf induced will be less compared to full-pitch. It is lesser than the value in the first case. Emf induced per coil side is E. If the coil span is less than the pole pitch, then the winding is said to be short-pitched. full, s. 2. D. The winding calculator allows you to find the optimum winding layout for your electric motor in a fast and convenient way. BUY Delmar's Standard Textbook Of ElectricityThe slots per pole per phase are 8 and the coil span is 20 slots. S 36 Solution From equation 5, pole pitch = P = 4 =9 Coil Span or coil pitch: It is the distance between the two active sides of the same coil under adjacent opposite poles. To improve the wave form only 80% of the pole pitch is wound. Determine the useful flux per pole. The spacing is expressed in terms of number of slots between the sides. The coil span equal to 180 electrical degrees: The coil span is less than 180 electrical degrees. The individual coils may have a span greater or less than a pole pitch but the average coil-span equals one pole-pitch. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. This answer is:Full-pitch windings have a coil pitch of 1, which means the coil span is equal to the pole pitch. 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 ____________. If the coil span is equal to the Pole pitch then it is called a full pitch coil. c. The two sides of a coil are places in two slots on stator surface. Despite its disadvantages, it is common in mass production. 10. Calculate the distribution factor for a single layer 36 slots 2-pole three-phase stator winding. . Calculate the emf generated in each phase when the machine runs at 375 rpm Hence, pitch factor or coil span factor K p = Cos(/2). 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. phase shift with emf induced in the other side of the coil. e. Then, the pitch factor will be equal. Wheres is the number of slots, and 2p is the number of poles [19]. 2. What are the different types of stator windings in induction motor? Ø. If the coil span factor is 0. Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span), by the number of slots per pole. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. Better emf waveform in case of generators 6. Boylestad. The pitch factor for third harmonic in an alternator having 18 slots per pole and coil span 5/6 of pole pitch is _. of phases = 3; No. Commutator pitch Y C = ±1. First. Pole pitch is always equal to 180o electrical. Result Number of. When the parallel path is twice the number of poles then it is known as Duplex Lap Winding. , Y = 2/3 τ p. With a full-pitch coil, the emfs induced in the two coil sides are in phase with each other and the resultant emf is the arithmetic sum of individual emfs. If the coil span is. It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. The pitch of the coil is 2 slot less than the pole pitch. A six pole, three phase AC generator has 72 slots, the coil span is 12. Question. The coil span is 150°. m. It is usually measured in terms of teeth, slots or electrical degrees. A pole pitch is always 180° electrical regardless of the number of poles on the machine. Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. what is coil pitch or coil span. ; Here, e = E 1 = E 2 = E. 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. 966 D. 966The pole pitch, mQ ′ ∕ p, is also fractional, so that the coil-span cannot be of full-pitch. It is always 180° electrical. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch. Get Coil Span or Coil Pitch Multiple Choice Questions (MCQ Quiz) with answers and detailed solutions. 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. The coil span is 150°. Note that although the span of a full-pitch coil is not an integer in a fractional-slot winding, the full-pitch coil is nevertheless an im- The correct answer is option 3. 10 such that two slots No. 1. m. 4. For the n th harmonic, the chording angle becomes nα° electrical. The skew factor reflects the flux reduction if the winding is angularly twisted along the axis. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. You can compare the maximum fundamental winding factor for different combinations of number of poles and number of slots, display the winding layout for different coil spans,. Coil span and commutato pitch b. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. The value of α will usually be given in the question, if not, then assume kc = 1. 12Wb and a third harmonic component. Coil is 12 slots. A. The pitch of the coil has 4 slots less than the pole pitch. The analyses of different six-pole winding configurations, obtained by changing the coil pitch number, winding layer, and stator slot number for the families of , are presented in Section 3. 6. y=Coil span τ=Z/2P is the Pole pitch or full span II. 707 B. 966 and 0. Here we can define one more term related to a coil called coil span. . Table of Contents Terms used in the armature winding Conductor Turn Coil Coil Side Front end and Back end connector Pole. The. Calculation:A coil rotated in a magnetic field induces current. 911 V B. ’s of consecutive turns c. It is usually measured in terms of teeth, slots or electrical degrees. 4 pole = 90º. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. 60º / 90º = 2/3. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a. in. , a pitch, or an pitch, etc. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. It is expressed in terms of electrical space degree. The phase winding factor for short-pitched coils is given by: K_p = cos(π * s / 2) where s is the coil span in terms of pole pitches. ∴ e = E 1 + E 2 = 2E. It is always less than unity. In SWAT-EM we can set the coil span explicite. 150 degree (electrical). the coil will be in 180o. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. g. The coil span is 150 electrical degrees. . Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. Wheres is the number of slots, and 2p is the number of poles [19]. Pitch: Pole and Winding • Pole pitch is the mechanical angle between adjacent poles, e. The pole pitch is 10 slots, and the coil pitch is 9 slots. When 40V DC voltage is applied to a single-phase AC motor, it draws 1A current. First. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° =. Calculate its coil span factor. The distance between the two sides of an individual coil of and AC armature winding id termed the coil pitch. 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. 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. When the coil span is equal to pole pitch (180 deg electrical), the winding is called full pitched winding. The induced emf in each coil side. , Y R = Y B − Y F . 3K views. When the coil span is lower than pole pitch, the phasor sum of conductor voltages is less than the arithmetic sum, because of vector addition. Distribute the winding uniformly under different poles d. For n th harmonic. MMF OF ARMATURE A. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . Front pitch (Y f):. For n th harmonic. fs. Armature Currents and MMF of 5-Phase Machine The armature currents of 5-phase machine can be expressed with formula (1). 05 Wb, sinusoidally distributed. (d)Find the number of turns per phase, Tph. What is the short pitch in electrical degrees. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. The distribution of upper-side voltage phasors is the same as that of coil voltage phasors,. the flux per pole has a fundamental component of 0. Petruzella. 5. The phase spread is 60° and the flux per pole is 25·8 × 10–3 weber. 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. 2 are short-pitched, full-pitched and over-pitched coils respectively. where: coil. The winding is double-layer. 1. The pole arc should be about 70% of pole pitch and length of core about 1. It may be the full pitched or short pitch. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. Figure 1. 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. Determine the phase and line voltages if the coil is full pitched. Identify number of rotor slots, number conductors / slot, coil span, number of slots per pole. e. 12 Wb and a 20% 3 rd harmonics. 966the coil span of the two slot‐pitch technique has been pro-posed, based on the ‘stator shifting’ concept [8, 9]. In this study, the electromagnetic performances of dual 3-phase permanent magnet (PM) machines with coil span of two slot-pitches are comparatively investigated. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. per Phase: Part 1In this video, I'll give you an idea how to derive the fundamental pitch factor (coil span f. Expert Solution. 15. 26. m. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. e. We will start Red at slot 1. 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 °. BUY. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. , or 5/6 × 180° = 150 electrical degrees. (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 . A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Machine, Nagpur Univ. p. the coils cannot be full - pitched; they may be short - pitched with 15 slots, or long - pitched with 16 slots. ISBN: 9780133923605. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. Answer Coil span factor = 0. When 40V DC voltage is applied to a single-phase AC motor, it draws 1A current. A 10 MVA, I KV, 50 Hz, 3-phase, star-connected synchronous seberatur is driven ur 300 r. Slots/pole/ph = m = 72/ (8×3) = 3. 955, whilst the second option gives (k_{sk1}) equal to 0. The part of the coil in which EMF is generated is known as _____. SEE MORE TEXTBOOKS. fs. See moreIf the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. – Comparator. Pole – pitch. The winding is 5/6 pitch. 31. The coil span or coil pitch for short or fractional pitch coil is less than 180 electrical degrees. It. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. A pitch in the "region" of 5/6 is most effective to reduce 5th and 7th harmonics. . P˚ = Pitch = coil span in no. Most windings have < . Let us consider, the coil has a pitch short by an angle α electrical degrees from the full pitch. The rotor is a large electromagnet. Electrical Engineering questions and answers. Assume the coil span as 150° electrical. If we used short pitched winding for armature winding than pitched factor is included in EMF equation in Alternator. F induced in one side of the coil will be in 180˚ phase shift with E. 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. 16 wb/pole and is distributed sinusoidally over the pole. In a 4-pole, 35 slot d. number of slots and a coil span of two slots require at least 18 slots. 24 where pole- pitch of 4 has been assumed), then winding is called full-pitched. If the angular distances between the two coil sides are less than one pole pitch, it is termed short pitch or fractional pitch coil. Comparator. The alternator has 18 slots per pole and the first coil lies in slots 1 and 16. A 4 pole, 12 slot lap wound dc armature has two coil side per slot. 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. A pole pitch is always 180° electrical regardless of the number of poles on the machine. What is the flux per pole if the voltage on open circuit is 1. 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. 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. Coilspan or coil-pitch. To get a coil around every tooth, we need two winding layers (double layer winding). 4. Generally. The winding is 5/6 pitch. (5/6) of a pole pitch. of a 10-pole three-phase 50Hz alternator with 2 slots per pole per phase and 4 conductors. e. A 4 pole, 12 slot lap wound dc armature has two coil side/slot. Back Pitch. coils having span which is equal to one pole-pitch i. For a full pitch coil, the value of pitch factor is unity whereas for its value is also unity for concentrated coils. L = πD/p = πD/ = 43 x 24 = 1048 ( satisfactory) Ex. 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. b. Coil Span: It is the angular distance between the two sides of the coil. Chording: with coil-span less than pole pitch 5. As shown in Fig. Corresponds to 180/12 i. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. arrow_forward. Its magnetic poles can be salient (protruding or sticking out from the surface of the rotor), as shown in Fig. C machine having a total number slots S = 16. The pole pitch, S/P, is also fractional, so that the coil-span cannot be of full-pitch. of consecu- tive turns (c) distribute the winding. c. Number of empty slots = 18 – 15 = 3 slots ( herefore alpha = 180^circ imes frac{3}{{18}} = 30^circ). advertisement. 9 and the efficiency is 0. Solution for For alternator having fractional pitch winding of 10/14 the coil span is 4. 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. 3, Fig. All coils in a phase are connected in series. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. As against this if coils are used in such a way that coil span is slightly less than a pole pitch i. armature, 180 electrical-degree coil span will be obtained when coils occupy. Coil Span:The angular distance between the centers of two adjacent poles on a machine is known as pole pitch or pole span. CONCENTRIC WINDING In unbifurcated concentric windings, the first of the q coils which is the smallest is thrown from the qth slot having coil-span, y = (τ – q + 1) and the second coil which is larger than the first coil will be thrown from Now, What is pitch factor? The ratio of phasor sum of induced EMFs per coil to the arithmetic sum of induced EMFs per coil is known as pitch factor K p or coil span factor K c. At this situation, two opposite sides of the coil lie under two opposite poles. The harmonic reduction in the voltage waveform of concentrated winding axial field PM machines is the subject of interest for many researchers. In a synchronous generator, what do fractional pitch and fractional slot windings mean?• (e) The coil span must be odd integer. Compared to the overlapping winding above we need only 3 slots for the two poles. A three phase, 50 Hz, 8 pole alternator has a star connected winding with 120 slots and 6 conductor per slot. 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. The arc diagram contains all the necessary information for connecting the pole-groups correctly. 1993) Example 37. Step by step Solved in 3 steps. 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. belt factor. IMs designed by utilising the winding configurations given in Section 3 are analysed and both SS and FW performance characteristics are presented. If the coil span is reduced by one slot, then the phase angle α between the induced EMFs in the two sides of the coil is given as.