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. 16 wb/pole and is distributed sinusoidally over the pole. Its value is always less than unity. The flux per pole has a fundamental component of 0. You can read more about Full Pitch and Short Pitch Winding at:. CONCENTRIC WINDING In unbifurcated concentric windings, the first of the q coils which is the smallest is thrown. A 144-slot stator has a whole coiled 12-pole three-phase winding. 3 percent. Pole Pitch: It is the angular distance between the two adjacent poles. 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. 24 where polepitch of 4 has been assumed), then winding is called full-pitched. Pitch Factor·· the ratio of the voltage generated in ti1e fractional-pitch coil to the voltage generated in the full-pitch. It. 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. 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. To get a coil around every tooth, we need two winding layers (double layer winding). 85. Hence, during rotation when one side of the coil comes under north pole, the other side of the coil comes under south pole. the coil will be in 180o. 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/. IV. e. The induced emf in each coil side. They save copper of end connections. 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). 0. 7. 1. Relation between frequency, speed and number of poles: Fig: 1. ed = electrical degree Example 2: Calculate the pole pitch for a three phase 4 pole ac machine having 36 stator slots. armature, 180 electrical-degree coil span will be obtained when coils occupy. Concept: Coil pitch or coil span: It is defined as the angular distance between the two coil sides of one coil. This lecture will discuss;1. (2) 𝑘 𝑐 𝑛 = c o s 𝑛 α 2. The pole pitch is always 180 degrees electrical regardless of the number of poles in a machine. 2. The spacing is expressed in terms of number of slots between the sides. 4. . (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. 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 . Question. Download Solution PDF. A pitch in the "region" of 5/6 is most effective to reduce 5th and 7th harmonics. If the coil span is equal to the Pole pitch then it is called a full pitch coil. If the coil span is less then one pole pitch than it is called short pitch 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). Calculation: Given that,For making coil span equal to a pole pitch in the armature winding of a d. Lap and Wave winding. Step by step Solved in 4. ; 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. the flux per pole has a fundamental component of 0. Coil span or coil pitch Ys: It is the distance between the two sides of a coil measured in terms of armature slots. Prelude to Synchronous Generator Induced E. 10 slots d. (8) A SIMPLE explanation of Full Pitch and Short Pitch Winding. All coils in a phase are connected in series. of a 10-pole three-phase 50Hz alternator with 2 slots per pole per phase and 4 conductors. 7 slots c. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. Alternatively, this type of coil is also called a short-pitch or chorded coil. IMs designed by utilising the winding configurations given in Section 3 are analysed and both SS and FW performance characteristics are presented. the distance between the two sides of coil is called the coil-pitch. Coil span Pole pitch Periodicities Winding factor. In a 4-pole, 35 slot d. e. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. 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. 3. 9: Rated speed (rpm) 170: Rated current (Arms) 3. Last Answer : If the coil span is equal to pole pitch, the winding is called as full pitched winding. The coil-span is 144° (electrical). 6. 11. The pole pitch is 35 cm, the core length 32 cm, and the stator coil span four fifth of the pole pitch. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. As against this if coils are used in such a way that coil span is slightly less than a pole pitch i. • In double layer windings used in. 86 O 119. The phase spread is 60° and the flux per pole is 25·8 × 10–3 weber. Chording: with coil-span less than pole pitch 5. 985 (ii) Slots per pole = 72/6=12, for a coil span of 10 slots, the coil is short pitched by 2 slots and the chording angle is ε=2γ and γ=180/12 ⇒ ε = 30° ⇒ K p =cos15°=0. The armature coils are all-connected in series. m. It mainly focuses on two PM machines with different slot/pole number combinations (N s /2p), that is, the 24-slot/10-pole and 24-slot/14-pole machines (2p = N s /2 ± 2). N st 2p r; 12 14 16 18 20 22; 12:. When a coil is having a span of 180° electrical, it is called a full-pitch coil. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. (16) k p1 = sin β 2 <1 where β is the coil span in °electrical, β=sα; s is the coil span in slots. can never be equal to pole pitch D. 0. The distance between the two sides of an individual coil of and AC armature winding id termed the coil pitch. Calculate the coil span factor or the pitch factor for the following windings: ( a) 54 stator slots, six-poles, when coil spans 1 to 8. If the machine gives 3300 V between lines on open circuit with sinusoidal flux distribution. Note. arrow_forward A. It means that coil span is 180 electrical degrees. 125 Wb and a 25% third component. Download Solution PDF. Give the values of front pitch, back-pitch and commutator pitch. Machine, Nagpur Univ. a. The part of the coil in which EMF is generated is known as _____. Figure below shows a short pitched coil. Corresponds to 180/12 i. Its flux per pole is 0. 26. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. Let us consider, the coil has a pitch short by an angle α electrical degrees from the full pitch. A full-pitch coil is one whose pitch is equal to the pole-pitch at the working harmonic. Solution : n = Slots/pole = 36/4 = 9. 8. 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). At this situation, two opposite sides of the coil lie under two opposite poles. Prelude to Synchronous Generator Induced E. 10 A three-phase, wye-connected alternator has 15 slots/pole. A 3-phase, 8-pole, 60-Hz, star-connected alternator has 96 slots with 10 turns per coil. It is always less than unity. It may be the full pitched or short pitch. The skew by one slot pitch gives the value of fundamental skew factor of 0. So if coil side in slot No. The coil span of the alternator is 1 to 8. In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch, back pitch, pole pitch, coil pitch, etc. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 6. However in practise this often isn’t the best choise because of the high harmonic content. Pitch factor:Concept: Pole Pitch: It is the angular distance between the two adjacent poles. 85 lagging. If the span of the coil is reduced by an angle 'α' of electrical, then the. 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 line to line induced emf for a 3 ϕ star connection is approximatelyCompute the phase and line voltage of a wye-connected three-phase, five-pole alternating current generator that runs at a speed of 1440rpm has a total slots of 135 slots with 4turns/coil. Generally. 6 turns. The slots per pole per phase are 8 and the coil span is 20 slots. The coil pitch is equivalent to the span, except that this term is used more often in a theoretical context and expressed in electrical degrees, or per-unit of a pole-pitch. of consecutive turns (c) distribute the winding uniformly under different poles (d) obtain a full-pitch winding. Since one pole presents 180 electrical space degrees so the slots pitch. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. The coil is also short-pitched (eg spam of two sides of. Problem. m. 15 Consider the armature conductor marked X in Fig 1. You can compare the maximum fundamental winding factor for different. 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. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . 4 pole = 90o. ; Here, e = E 1 = E 2 = E. e. the flux per pole has a fundamental component of 0. 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. Sketch the winding over a pole pitch, indicating the location of the conductor of each phase. Calculate the distribution factor for a single layer 36 slots 2-pole three-phase stator winding. BUY. c. Show transcribed image text There are 3 steps to solve this one. , coil span is 180º electrical) is called a full-pitch coil. 6. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. 10 are one pole pitch or n slots or 180° electrical apart, the coil is called full pitch coil. Hence emf induced in one side of. For example if S/P = 10. It is one pole pitch. Answer: a. 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. 60o groups, 2-layer winding is used. *. Let the coil have a pitch short by angle q electrical space degrees from full pitch and induced emf in each coil side be E. Every coil is connected to the commutator. There are B coil groups of (A+1) coils, that is, 1 coilIf the pole span or coil pitch is equal to the pole pitch (as in the case of coil A in Fig. in them are additive. Download these Free Coil Span or Coil Pitch MCQ Quiz Pdf and prepare for your upcoming exams Like Banking, SSC, Railway, UPSC, State PSC. Transcribed image text: 1. Identify the approximate diameter and length of stator core,. Commutator pitch. Fractional pitched windings are purposely used to effect a substantial saving in copper of the end connection and for improving commutation . 0 i D. The pole pitch is 35 cm, the core length 32 cm, and the stator coil span coil span four fifth of the pole pitch. Pole arc/ pole pitch = core length/ pole pitch = 0. The skew factor reflects the flux reduction if the winding is angularly twisted along the axis. arrow_forward. 06 weber distributed sinusoidally over the pole. DARWIN M. kp: 0. ∴ e = E 1 + E 2 = 2E. 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. fs. A 6-pole, 3-phase, 60 cycle alternator has 12 slots per pole and four conductors per slot. Generators 897 winding is fractional-pitched. . 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: (b) A 4 pole AC machine has its winding housed in 48 slots with coils of span 11/12 th of a pole…A pole pitch is always 180 electrical degrees, regardless of the number of poles on the machine. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. Emf induced per coil side is E. The primary reason for making the coil span of a d. 25 slots. Pole pitch is always equal to 180o. It equals pole pitch = Z P . $$\mathrm{Slot\:per\:pole =\frac{90}{6}= 15}$$ For a full-pitch coil, the coil span is 15 slots. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. Robert L. arrow_forward. Expert Solution. m. m. Calculate the emf generated in each phase when the machine runs at 375 rpmHey Aspirants. . ; Coil Span: It is the angular distance between the two sides of the coil. , pole-pitch ) is known as 'Full Pitch'. 0. the core length 32 cm, and. The slots per pole per phase are 8 and the coil span is 20 slots. Coil span (also known as coil pitch) is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. Question: 2 Problem 2: The flux distribution curve of a smooth core 50HZ generator is B(0) = sin 8 +0. The coil-span chosen is of course less than the full-pitch. If coil span is equal to pole pitch then it is called full pitch coil. 24 D. The average pitch Y A = 2 B F Y Y +. 956 1. 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. (BTL-1) 4. f. 8. This number is known as coil span. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a full-pitch winding. Despite its disadvantages, it is common in mass production. What is the coil span for a 2 pole 18 slot machine? a) 9 b) 4. 10. The value of α will usually be given in the question, if not, then assume kc = 1. 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. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. 2:. For the n th harmonic, the chording angle becomes nα° electrical. 10 such that two slots No. In a 4-pole, 35 slot dc armature, 180 electrical degree coil span will be obtained when coils occupy _____ slots. 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. Looking at the diagram in the question. what is coil pitch or coil span. See solution. 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. 60 hz, 10-pole alternator has 120 slots and 4 turns in every coil. 100+ Subjects. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. The separation between the top and bottom sides of a coil is called Coil span. 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. The coil span is 150 electrical degrees. Lap winding • Suppose we want to make a lap winding for a P = 4 pole D. AC compound generator usually has lower resistance. Identify number of rotor slots, number conductors / slot, coil span, number of slots per pole. Then, the pitch factor will be equal. 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. In such coils, the two coil sides are not under the poles. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. EXAMPLE: Calculate the pitch factor for a alternator winding with 36 slots, 4. 14. Determine the equation for the emf induced in one turn, and its RMS value. ); and k y is the short pitch factor. Introductory Circuit Analysis (13th Edition) 13th Edition. 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. Last edited by markadlerdallas. BUY. 163Wb. What are the different types of stator windings in induction motor? Ø. 1 times the pole arc. 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. ( b) 42 stator slots, four-poles, coil. If the coil span factor is 0. per slots, in a double layer. It is usually measured in terms of teeth, slots or electrical degrees. , or 5/6 × 180° = 150 electrical degrees. 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. Calculation:A coil rotated in a magnetic field induces current. For n th harmonic. 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. Copy. In a synchronous generator, what do fractional pitch and fractional slot windings mean?• (e) The coil span must be odd integer. In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch, back pitch, pole pitch, coil pitch, etc. • Winding pitch is the coil span divided by the pole pitch, e. The coil span is 150°. 14. The correct answer is option 2): 5 slots Concept: Coil span (also known as coil pitch) is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them. 1, if the coil sides are placed in slots 1 and 7, then it is full-pitched. Figure 8 compares computed waveforms of phase back emf. MARASIGAN, REE, RME Figure 11 If the coil span is less than the pole pitch (as in coil B where the coil pitch is ¾ of the pole pitch) then the winding is fractional pitched. K pn = cos nα/2. 772 x 10-3 Wb. 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. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. 125 Wb and a. It is usually measured in terms of teeth, slots or electrical degrees. 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). e. Only 100% coil pitch in a two pole machine means half the air-gap circumference. ; It means one side of the coil in a particular slot, after how many conjugative slots, the other side of the same coil is placed. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. The coil span is 160°. This. 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 0. Front connections 8+7=15; 30+7-30=7 8. 966 and 0. 1: How to get flux, based on the rotor, through a coilspan coil (the coil span is closest to pole pitch, 3. I need answer within 20 minutes please please with my best wishes. If the coil span is. Hence emf induced in one side of. Calculared the flux per pole required to give Il kV line voltage on open circuit voltage. 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. (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 . 966 D. Boylestad. in the two sides of the coil. Duplex Lap Winding. If we used short pitched winding for armature winding than pitched factor is included in EMF equation in Alternator. For a full pitch coil, the value of pitch factor is unity whereas for its value is also unity for concentrated coils. First. Distribute the winding uniformly under different poles d. The arithmetic sum of induced emfs is 2E. * This angle is known as chording angle and the winding employing short-pitched coils is called chorded winding. Pole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical Degree - YouTube Hey Aspirants. D. Assume that the coil span is 150° electrical. If fractional pitch is used, the emfs in the two coil sides are out of phase, which reduces the emf. Comparator. A pole pitch is always 180° electrical regardless of the number of poles on the machine. 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. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. Here ξ is the chorded angle or short pitch angle. 25 = 6 and 1/4 slots. It is defined as the angular distance between the central line of one pole to the central line of the next pole. When a coil. Kr ==sink 2 · Kp =pitch factor in dcci111al p" =span of the coil in electrical degrees. 8 slots b. m. #Alternator #Protectionofalternator#elect. 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. The pole pitch, S/P, is also fractional, so that the coil-span cannot be of full-pitch. Determine the useful flux per pole. Wheres is the number of slots, and 2p is the number of poles [19]. y=Coil span τ=Z/2P is the Pole pitch or full span II. Pole pitch is defined as the angular distance between the central line of one pole to the central line of the next pole. 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. Coil span is defined as the peripheral distance between two sides of a coil. 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 ____________. 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. 2. is known as coil span. When measured in electrical degrees one pole itch is equal to 1800. 7. Step by step Solved in 2. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. The total flux per pole is 10⁶ lines. 24 where pole- pitch of 4 has been assumed), then winding is called full-pitched. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. In a 4-pole, 35 slot dc armature, 180 electrical degree coil span will be obtained when coils occupy _____ slots. . p. In a 4-pole, 35 slot d. • Pitch of a Winding (Y) In general, it may be defined as the distance round the armature between. 339 IC function as. If the coil pitch is less than one pole pitch, the coil is called the short-pitch coil or fractional-pitch coil. There are 2 coil sides per slot. K pn = cos nα/2. A pole pitch is always 180° electrical regardless of the number of poles on the machine. Wheres is the number of slots, and 2p is the number of poles [19]. Advantages of short pitched,( chorded, fractional slot) windings are:-The amount of copper used in the overhang (end winding) reduced and hence a saving on copper,Based on pitch of the coil (i) full pitched (ii) short pitched windings. Let us assume that, a coil is short pitched by an angle α (electrical degree). The usefulness of winding distribution and chording in reducing or eliminating harmonics will be touched on in. The coil span is 150 , the flux/pole has a fundamental components of 0. 0 B. of slots per pole = 15 but coil span is… question_answer Q: A synchronous generator is generating 320 V at 55 Hz at a field current of 3. Pole pitch is always equal to 180o. 025 Wb entering the armature from each north pole, and this flux is sinusoidally distributed along the air gap. e. ∴ e = E 1 + E 2 = 2E. Fractional slot winding 6. arrow_forward. . 1. In a full pitch coil, the coil span will be 180° electrical (equal to pole pitch). • To view the coil sides / coils, we must look below from above the slots as depicted in figure. A 4 pole, 12 slot lap wound dc armature has two coil side/slot. 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,. A 4 pole, 12 slot lap wound dc armature has two coil side per slot. 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. 5. In a short pitch coil, the coil span will be (180 -. The coil span is 160°. Resultant flux in the air gap is 55 mWb per pole. The pole pitch is 35 cm.