A six pole, three phase AC generator has 72 slots, the coil span is 12. The commutation is. Study with Quizlet and memorize flashcards containing terms like A lap winding, Twice, Full-pitch and more. Pole pitch. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. B. Distribute the winding uniformly under different poles d. Use a diagram like that shown in fig. e. 125 Wb and a 25% third component. p. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. . 6 turns. BUY. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. The primary reason for making the coil span of a d. A pole pitch in an electrical machine is equal to 180° electrical. $$\mathrm{Slot\:per\:pole =\frac{90}{6}= 15}$$ For a full-pitch coil, the coil span is 15 slots. Example: the throw could be to 9 meaning that one side of the coil is inserted in slot #1, and the other side in slot #9. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. DARWIN M. ( 2) The harmonic voltages decrease in a short pitch coil, thereby improving the waveform of the induced voltage in the winding. , 5 slot‐pitches in Figure 2a) [8, 9]. m. round the coil which is the vector sum of e. The slots per pole per phase are 8 and the coil span is 20 slots. 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. Thus, the total. A=2, B=1 and C=2 and D=5. 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. f. Calculate the emf generated in each phase when the machine runs at 375 rpmHey Aspirants. 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. 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. 11. 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. For alternator having fractional pitch winding of 8/14 the coil span is 102. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. p. Here, e = E 1 = E 2 = E. In this paper, the influence of changing the span of the concentrated coil for a certain pole pitch on the harmonic content in the output voltage. full, s. The armature coils are all connected in series. Result Number of. 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. 4. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. D. 05 Wb, sinusoidally distributed. Question For a 3-phase stator winding having 6 slots per pole per phase and coil span of 13 slot pitch, the value of pitch factor will be: BUY. For example if S/P = 10. 7. The commutator is also known as a reverser. It is using an armature winding which is short pitched by one slot. Here, e = E 1 = E 2 = E. Since the winding is full pitched coil, so the pitch of each. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. Hence E. Coil span is defined as the peripheral distance between two sides of a coil. The coil span is 10 slots. 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. We must note that the coil-pitch and flux barriers of the NC2 are adjusted as shown in. If 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. If the generator is running at 1200 rpm, find the average voltage generated between brushes for wave winding. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. e. In this. #Alternator #Protectionofalternator#elect. 11. The Separation between the top and bottom sides of a coil is known as back pitch and is represented by (Y b). 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. Coil Span: The number of core slots spanned by the sides of the coil. If the coil span is less than the pole pitch then the coil is said to be a short-pitched 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. Explain the following armature winding terminologies (i)commutator Pitch (ii)Coil Side (iii)Pole Pitch. arrow_forward. Alternator connections: star or delta connections of alternators suppress triplen harmonics from appearing across the lines 1. 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. Armature Currents and MMF of 5-Phase Machine The armature currents of 5-phase machine can be expressed with formula (1). The coils are made up of 8 turns, and the windings are double layer. Theta (electrical)=p/2 (theta (mechanical)) What is the formula for electrical angle. of phases = 3; No. This lecture will discuss;1. A 4 pole AC machine has its winding housed in 48 slots with coils of span 11/12 th of a pole. Condition for designing a Mush winding:- 21. ∴ e = E 1 + E 2 = 2E. . c. Calculate the distribu factor for a 36-slot. In an alternator, for a coil having a span of 2/3 of pole pitch,. The coil span is 160°. 15. machines with. When the coil span is less than pole pitch (180 deg electrical), the winding is called short pitched or chorded. 015 Wb. 1. 7. 1 and No. It may be the full pitched or short pitch. ∴ e = E 1 + E 2 = 2E. As against this if coils are used in such a way that coil span is slightly less than a pole pitch i. The pole pitch is 10 slots, and the coil pitch is 9 slots. The harmonic reduction in the voltage waveform of concentrated winding axial field PM machines is the subject of interest for many researchers. armature, 180 electrical-degree coil span will be obtained when coils occupy. 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. voltage wave form which resembles a sinusoid to a better degree than that in a full pitch winding Example 1: Calculate the K d for a machine having 9 slots per pole for the following cases: a) A 3 phase winding with 120 0phase groups b) A 3 phase winding with 60 0 phase groups Solution: 0 209 180 a) Since one phase occupies. 24 B where coil pitch is 3/4th of the pole pitch), then the D. Here, e = E 1 = E 2 = E. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. M. fs. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. 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. Front connections 8+7=15; 30+7-30=7 8. ∴ e = E 1 + E 2 = 2E. Determine the number of conductors in series per phase. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. It. Back Pitch. An alternator having 10-poles, 3-phase, and 60 Hz has 8 conductors per slot in single layer arrangement with 4 slots/pole/phase. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. Commutator pitch of a progressive lap winding is yc = +1. The coil span should be minimum of about 8. A) 1. F = 0. To understand, it simply means that one parallel path is in N-Pole and another parallel path in S-pole. 5 c) 18 d) 6 View Answer. in the two coil sides. Petruzella. Short-pitched coils are deliberately used because of the following advantages: 1. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. When measured in electrical degrees one pole itch is equal to 1800. Compared to the overlapping winding above we need only 3 slots for the two poles. – Comparator. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. Author: Frank D. Wheres is the number of slots, and 2p is the number of poles [19]. c. 1993) Example 37. – Comparator. (ii) Pole pitch: The over hang portion of the coils depend upon the coil. 125 Wb and a. Coil–span or coil-pitch. 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). The phase spread is 60° and the flux per pole is 25-8 x 10 weber. the north pole, the other coil side should be under the center of the south pole. 7. 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,. It indicates how the coils are spaced out on the armature core. Obtain a full-pitch winding. Coil Span (ii) Resultant Pitch. Register to editPitch factor problem. 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. 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. Calculation:When the coil sides forming a coil are spaced exactly one pole pitch a part they are said to be of full-pitch. Required: a. In this. The slots per pole per phase are 8 and the coil span is 20 slots. The armature winding is housed in 360 stors with 6 conductors per slot. Assume that the coil span is 150° electrical. Hence, the total e. Pole pitch is always equal to 180o. The dc armature winding in which coil sides are a pole pitch apart is called ____ winding – Full- pitch. It is usually measured in terms of teeth, slots or electrical degrees. c. a coil. If the coil span is equal to the Pole pitch then it is called a full pitch coil. Expert Solution. Coil span Pole pitch Periodicities Winding factor. The coils are place in 60 uniformly distributed slots around the inner perimeter of the stator. Pole pitch is always equal to 180. The coil pitch is 5/6th of the full pitch and the flux per pole is o. 0 i D. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. 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. of poles, P= 4 No, of slots = 24; No. 2 Selecting the coil span for a given pole pitch. of consecu- tive turns (c) distribute the winding. They save copper of end connections. (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. in them are additive. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. In a 4 pole, 3 phase alternator, armature has 36 slots. 15 situated at the center of an N pole rotating in clockwise direction. f. In practice, coil pitch (or Span) as low as eight-tenths of a Pole Pitch, is employed without much serious reduction in emf. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a. 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 skew factor reflects the flux reduction if the winding is angularly twisted along the axis. ÐÏ à¡± á> þÿ ” — þÿÿÿt u v w x y z { | } ~ € ‚ ƒ „. Coil–span or coil-pitch. ; 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. y=Coil span τ=Z/2P is the Pole pitch or full span II. 9 and the efficiency is 0. Commutator bars per pole. 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. less than 180° electrical, the coils are called, short pitched coils or fractional pitched coils. This chapter covers the calculation of winding factors and armature MMFs, harmonic analysis of armature MMFs. The dc armature winding in which coil sides are a pole pitch apart is called ____ winding – Full- pitch. d5. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. The average pitch Y A = 2 B F Y Y +. • So coil span is 16/4 = 4. electrical degrees indicate the amount the currents in conductors has changed. 3. Corresponds to 180/12 i. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. If each coil spans 8 slot pitches, what is the value…Front pitch: The distance between the last side of the first coil and first side of the second coil is called the front pitch. 0 B. can never be equal to pole pitch D. 1 . g. If each coil is short pitched by an angle of 36 ∘ electrical. Use a diagram like that shown in fig. Fig. the coil span is (180-ε), therefore the emf induced in these coil sides will also be separated by this angle. In this case, we have a 10 pole alternator with coils wound in a fractional pitch of 18/21. Machine, Nagpur Univ. The slots per pole per phase are 8 and the coil span is 20 slots. Determine the pitch (or coil span) factors for the winding , 96 Stator slots ,4 poles, coil span 1 to 18 13. Calculate the average voltage generated in a six-turn full pitch coil of a 25 cycle alternator if the. Determine the pitch (or coil span) factors for the winding ,24 Stator slots ,4 poles, coil span 1 to 5 12. 1, or nonsalient (flush with the surface of the rotor), as shown in Fig. The individual coils may have a span greater or less than a pole pitch but the average coil-span equals one pole-pitch. Problem. pole pitch5. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Type your question here Calculate the voltage per phase for a 3-phase 1500 rpm, 4-pole alternator having a 16 conductors per slot connected in two layers. Thus, the total. Last updated on Nov 23, 2023 UPSC IES Final Result 2023 Out on 22nd November 2023!If 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. The back pitch and front pitch adopted could be respectively. Understand what Full Pitch and Short Pitch Windings are, and what Coil Span is. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. 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. The pitch factor for third harmonic in an alternator having 18 slots per pole and coil span 5/6 of pole pitch is _. 0. ISBN: 9780073373843. Pole – pitch. On the other hand, if its span is less than a pole-pitch. TERMS Coil Throw: The location in an armature core of the sides of a coil starting in slot number one (1). BUY Delmar's Standard Textbook Of ElectricityThe slots per pole per phase are 8 and the coil span is 20 slots. 36 stator slots, 4-pole, coil span 1to 8 ii. in. Fractional pitched windings are purposely used to effect a substantial saving in copper of the end connection and for improving commutation . The coil span is 150 electrical degrees. † ‡ ˆ ‰ Š ‹ Œ Ž ‘ ’ “ ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿPitch factor: Full-pitched coils i. The coil span is 160°. ) 2 Angle by which the coil is short pitched, B = a = 30° Distribution factor, Ky = Pitch factor or coil span factor, K, = cos 6 = cos. 163Wb. Calculate the pitch and distribution factors for the fundamental, the third, and the fifth harmonics in the phase voltage. The winding spans all11. the coils cannot be full - pitched; they may be short - pitched with 15 slots, or long - pitched with 16 slots. c. For n th harmonic. the flux per. For a simplex lap winding, the commutator pitch YC = 1 and coil span YS ~ pole pitch. 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. But, the given coil is short-pitched so that the coil span is $$\mathrm{coil\:span = (14 − 1)β = 13β}$$ $$\mathrm{∴\:α = (15 − 13)β = 2β = 2 × 12° = 24°}$$ Winding factor for fundamental component Pole pitchis defined as the peripheral distance between the center of two adjacent poles in a DC machine. Because a chording more than 1/3 pole pitch would noticeably reduce the phase emf. Coil – span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. ( ) () ⎪ ⎪ ⎪ ⎩ ⎪⎪ ⎪ ⎨ ⎧ = − = − = − = − = sin 8 /5 sin 6 /5 sin. The fundamental pitch. 36K subscribers Subscribe 9. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. Prelude to Synchronous Generator Induced E. Short-pitched coils are deliberately used because of the following advantages: 1. 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. Pole – pitch. 09 O4. 👉 (2008-2018) With solution, BRANCH Wise Click the Link-ELECTRICAL. The flux per pole is 0. fs. m. o. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. The winding is wye-connected. 2-pole star-connected, armature winding of a generator has 6 slots per phase. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch. The armature coils are all-connected in series. The term “winding pitch” refers to the ratio of the number of winding slots enclosed by each coil in the alternator stator to the number of winding slots per generator pole. Pitch factor:Concept: Pole Pitch: It is the angular distance between the two adjacent poles. It is usually measured in terms of teeth, slots or electrical degrees. The four coils of Phase A would span between slots 1 and 6, slots 2 and 7, slots 7 and 12 and slots 8 and 1. Determine the equation for the. 6A. 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. In other words, the distance between the two coil sides of a coil will be equal to the distance. The coil-span chosen is of course less than the full-pitch. All coils in a phase are connected in series. Last Answer : If the coil span is equal to pole pitch, the winding is called as full pitched winding. e. It is sometimes convenient to speak of an armature coil span as having a fractional pitch expressed as a fraction e. N st 2p r; 12 14 16 18 20 22; 12:. It is always 180° electrical. In such coils, the two coil sides are not under the poles. 86 O 119. A. 4 pole three phase winding. Q1/ Calculate the voltage per phase for a 3-phase 1500 rpm, 4-pole alternator having a 16 conductors per slot connected in two layers. Distribute the winding uniformly under different poles d. Full Pitch and. per Phase: Part 1In this video, I'll give you an idea how to derive the fundamental pitch factor (coil span f. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. the coil-span needs to be increased, so as to link a higher flux. BUY. 12Wb and a third harmonic component. In the considered motor, the fundamental winding factor is equal to the skew factor due to unity fundamental coil-span and distribution factors. 966 Distribution factor = 0. phase shift with emf induced in the other side of the coil. 24 where polepitch of 4 has been assumed), then winding is called full-pitched. A 4-pole, 3-phase synchronous machine has 48 slots. 5 are the stator low-order voltage harmonics for the different motors with 120°, 140°, 160° and 180° coil pitch at half load, full load and overload, respectively. 1 times the pole arc. Generators 897 winding is fractional-pitched. For 20 slots, 4 polesThe winding of a 4-pole alternator having 36 slots and coils and a coil span of 1 to 8. Q3- A/ 10 MVA, 11 KV, 50 Hz, 3-phase star-connected alternator s driven at 300 RPM. What is a coil span? The coil span is the distance between one conductor of a certain phase and the corresponding return conductor. The usefulness of winding distribution and chording in reducing or eliminating harmonics will be touched on in. 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. fs. • Winding pitch is the coil span divided by the pole pitch, e. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. Solution for For alternator having fractional pitch of 11/12 the coil span is a. ISBN: 9780073373843. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. There’s just one step to solve this. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. For a short pitch coil KC. If the pole span or coil pitch is equal to the pole pitch (as in the case of coil A where pole-pitch of 4 has been. 851: D) 0. 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. Hence, the pole pitch of that DC machine would be 24. Coil Span: It is the angular distance between the two sides of the coil. 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. B. View full document. Commutator pitch. Pole Pitch, Coil Span, Back Pitch, Front Pitch, Commutator Pitch in Armature Winding of DC Machines are explained in this video. Determine the phase and line voltages if the coil is full pitched. 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 °. e. In a 4-pole, 35 slot dc armature, 180 electrical degree coil span will be obtained when coils occupy _____ slots. 40 O 2. 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. In a 4-pole, 35 slot d. Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span), by the number of slots per pole. 3, Fig. ( b) 42 stator slots, four-poles, coil spans 1 to 10. 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 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. 1. in. Petruzella. It is one pole pitch. The flux per pole is 0. 12Wb. 71 O 120. F. 339 IC function as. 10 A three-phase, wye-connected alternator has 15 slots/pole. 866. Therefore one coil, such as coil 1 which traverses slot 1 and 7 falls under the north and south pole exactly because they are 180º apart as seen in the image above. There. Publisher: McGraw-Hill Education. 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). Coil Span: It is the angular distance between the two sides of the coil. A 3-phase, 4 pole, Y- connected alternator has 72 slots with two conductors per slot. Pole pitch is the mechanical angle between adjacent poles, e. coil pitch in terms of slots4. It equals pole pitch = Z P . Where n is the nth harmonic. 1: How to get flux, based on the rotor, through a coilspan coil (the coil span is closest to pole pitch, 3. In this alternator one pole spans twelve slots.