arrow_forward How to calculate the pitch factor of a 8 pole alternator with an armature wound coils having 18 / 24 fractioanl pitch. Coil Span (ii) Resultant Pitch. What is the coil span for a 2 pole 18 slot machine? a) 9 b) 4. ) A 6-pole, 3-phase, 60-Hz alternator has 12 slots per pole and four conductors per slot. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 4, Fig. . 4 pole three phase winding. 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. What is the pitch factor? Solution: Example 2: A 400 kVA, 6 kV, 60-cycle Y-connected alternator has the following data: poles = 6; conductors per slot = 12; total slots = 54; winding = two-layer lap; pitch = 8/9; flux per pole = 4 x 107 maxwells. First. 26. fs. 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. The coil span is 150 electrical degrees. fs. 60o groups, 2-layer winding is used. M. Pole pitch is always equal to 180o. Commutator pitch Y C = ±1. The commutation is improved in short-pitched coil, but the emf induced will be less compared to full-pitch. A pole pitch is always 180° electrical regardless of the number of poles on the machine. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. TYPES OF AC MACHINES WINDINGS. 0. Result Number of. Find the terminal voltageon open circuit. Determine the pitch (or coil span) factors for the winding , 96 Stator slots ,4 poles, coil span 1 to 18 13. The pole pitch is 35cm, the core length is 32cm & sta- 4th tor coil span is of pole pitch. It is sometimes convenient to speak of an armature coil span as having a fractional pitch expressed as a fraction e. 956, 0,647 02A pole pitch covers 25/4 = 6. The winding is wye-connected. Short Pitch Coil. 966The pole pitch, mQ ′ ∕ p, is also fractional, so that the coil-span cannot be of full-pitch. (Elect. 26. The pole pitch is 35 cm. Back pitch: The distance between the two sides of a coil in the back of the armature is called back pitch. 1. Coil span is simply a peripheral distance between two sides of a coil. A 4 pole, 12 slot lap wound dc armature has two coil side/slot. 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. So if coil span is ‘n’ slots or 180° electrical the coil is called 180° full pitch coil. If the coil span is equal to the Pole pitch then it is called a full pitch coil. m. 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. Q3- A/ 10 MVA, 11 KV, 50 Hz, 3-phase star-connected alternator s driven at 300 RPM. Slots/pole/ph = m = 72/ (8×3) = 3. Here ξ is the chorded angle or short pitch angle. 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. Hence, the pitch factor or the coil span factor for the n th harmonic is given by, kcn = cos nα 2. The armature coils are all connected in series. K pn = cos nα/2. There are 0. A coil whose sides are separated by one pole pitch (i. On the other hand, if its span is less than a pole-pitch. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. 60 hz, 10-pole alternator has 120 slots and 4 turns in every coil. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. advertisement. Study with Quizlet and memorize flashcards containing terms like A lap winding, Twice, Full-pitch and more. This video lecture provides full understanding of pole pitch and coil pitch with examples. N st 2p r; 12 14 16 18 20 22; 12:. Explanation: Pole pitch is called as center to center distance between two adjacent poles. 1 times the pole arc. The winding spans all11. 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. 0:00 / 15:33 What is Coil Pitch and Pole Pitch /what is electrical and mechanical angle in Urdu/Hindi IK LECTURES 2. Pole pitch is the electrical angle between the north pole and. ( b) 42 stator slots, four-poles, coil spans 1 to 10. Give the values of front pitch, back-pitch and commutator pitch. 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. B. Here we can define one more term related to a coil called coil span. The theoretical coil pitch yp (or span) is the number of slot pitches between the two coil-sides of the same coil. The commutation is. Calculate the pitch factor of the coil for 3 rd harmonic. 0 i D. round the coil which is the vector sum of e. e. † ‡ ˆ ‰ Š ‹ Œ Ž ‘ ’ “ ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿPitch factor: Full-pitched coils i. Pole – pitch. DARWIN M. 966the coil span of the two slot‐pitch technique has been pro-posed, based on the ‘stator shifting’ concept [8, 9]. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. – Comparator. It is usually measured in terms of teeth, slots or electrical degrees. In this video lecture you will learn about electrical angle,mechani. The skew factor reflects the flux reduction if the winding is angularly twisted along the axis. The slots per pole per phase are 8 and the coil span is 20 slots. We make the coil span less than 180 degrees electrical space degrees in a fractional pitch winding. 851: D) 0. It is usually measured in terms of teeth, slots or electrical degrees. 1 is connected to coil side in slot No. 4. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. For a 3-phase winding with 6 slots per pole per phase and with coil span of 15 slot, the value of pitch factor is A. It is expressed in terms of electrical space degree. Pole pitch = 180 electrical degrees = S/P = 2C/P. Y-connected alternator has 9 slots per pole and a full-pitch. * This angle is known as chording angle and the winding employing short-pitched coils is called chorded winding. It may be the full pitched or short pitch. The coil span is 160°. 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. When measured in electrical degrees one pole itch is equal to 1800. For the n th harmonic, the chording angle becomes nα° electrical. 1 times the pole arc. 4 Winding Factor Both distribution factor (Kd) and pitch factor Kp together is known as winding factor Kw. If the coil span is equal to the Pole pitch then it is called a full pitch coil. Pole pitch is always equal to 180o. The Separation between the top and bottom sides of a coil is known as back pitch and is represented by (Y b). Calculate the RMS value of the induced emf per phase. 25 O 5. 15 Consider the armature conductor marked X in Fig 1. 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. 772 x 10-3 Wb. Since one pole presents 180 electrical space degrees so the slots pitch. Let us consider, the coil has a pitch short by an angle α electrical degrees from the full pitch. Machine, Nagpur Univ. If the coil span is less than the pole pitch (as in coil Fig. A: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. In a fractional pitch winding, the coil span is made less than 180 degrees electrical space. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. 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. This number is known as coil span. fs. In SWAT-EM the coil span is given in number of slots. Calculate its coil span factor. Thus, the total. 86 O 119. The fundamental flux per pole is 0. , the case of short-pitch coil, the voltages generated in each coil side are not in phase. 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. Supposing that each coil under the pole pitch has. 165 degrees. It may be the full pitched or short pitch. 15. 6A. The pole pitch is always 180 degrees electrical regardless of the number of poles in a machine. . MMF OF ARMATURE A. m. In general, if the coil span falls short of full-pitch by an angle α (electrical)*, then kc = cos α/2. If each coil is short pitched by an angle of 36 ∘ electrical. it is said to the a fractional-pitch. m. 0. , a pitch, or an pitch, etc. e. Normally the nearest whole number is selected which is 6 in present case. m. It is using an armature winding which is short pitched by one slot. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. A pole pitch is always 180° electrical regardless of the number of poles on the machine. 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. (c)Find the number of coils in a coil group, m. Calculate the distribu factor for a 36-slot. Looking at the diagram in the question. 7. The value of α will usually be given in the question, if not, then assume kc = 1. There’s just one step to solve this. Note. The pitch factor. Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span), by the number of slots per pole. The flux per pole has a fundamental component of 0. of poles, P= 4 No, of slots = 24; No. There are 4conductors per slot and a sinusoidally distributed flux per pole of 36mWb. it is said to the a fractional-pitch coil. In a full pitch coil, the coil span will be 180° electrical (equal to pole pitch). 0 C. Resultant pitch Y R is even, being the arithmetical difference of two odd numbers, i. 1, or nonsalient (flush with the surface of the rotor), as shown in Fig. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. Pole pitch is the peripheral distance between two adjacent poles. In a 4-pole, 35 slot d. 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. A 3 phase 1800 kVA, 3 kV, 50 Hz, 250 rpm, salient pole. 1 and No. Answer: a. Understand what Full Pitch and Short Pitch Windings are, and what Coil Span is. The induced emf in each coil side. It has key variables such as Pole Pitch (back and front pitch, resultant pitch and communicator pitch, Coil Span, Commutator Pitch. We will start Red at slot 1. The flux per pole has a fundamental component of 0. It is given by K p = cos (α/2) Where α is the short pitch or chording angle. To get a coil around every tooth, we need two winding layers (double layer winding). 14. 26. m. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. Calculate the distribution factor for a single layer 36 slots 2-pole three-phase stator winding. The coil span of a full pitch coil is always 180° electrical. A pole pitch in an electrical machine is equal to 180° electrical. Here, e = E 1 = E 2 = E. Relation between frequency, speed and number of poles: Fig: 1. What are the different types of stator windings in induction motor? Ø. 12 Wb and a. arrow_forward. The commutator is also known as a reverser. Key. e. 259 C. [Answer: 0. m. At this situation, two opposite sides of the coil lie under two opposite poles. Pole pitch is always equal to 180o. Figure 4 shows the flux distribution linked to a short-pitch coil. The separation between the top and bottom sides of a coil is called Coil span. 13. The slots per pole per phase are 8 and the coil span is 20 slots. 16 wb/pole and is distributed sinusoidally over the pole. ∴ e = E 1 + E 2 = 2E. The coil span is five-sixth of a pole pitch. 36K subscribers Subscribe 9. 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. The alternator has 18 slots per pole and the first coil lies in slots 1 and 16. 16 wb/pole and is distributed sinusoidally over the pole. Create a winding table for the given armature: Winding 1: 4 pole, 11 slots, 11 commutator segments, double layer, progressive, simplex WAVE winding Show the solutions. 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. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. 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 displacement between the sides of the coil is called the coil span. Generators 897. 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. what is coil pitch or coil span. ISBN: 9780133923605. Coil Span: It is the angular distance between the two sides of the coil. e. If the coil span is less then one pole pitch than it is called short pitch coil. Q: For alternator having fractional pitch winding of 8/14 the coil span is 102. Thus, the total. Armature Currents and MMF of 5-Phase Machine The armature currents of 5-phase machine can be expressed with formula (1). In other words, the distance between the two coil sides of a coil will be equal to the distance. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. 455 V D. The value of α will usually be given in the question, if not, then assume kc = 1. it is said to the a fractional-pitch coil. arrow_forward. In a 4-pole, 35 slot d. arrow_forward. With a full-pitch coil, the emfs induced in the two coil sides are. g. In a short pitch coil, the coil span will be (180 -. Most windings have < . 10 are one pole pitch or n slots or 180° electrical apart, the coil is called full pitch coil. The coil is also short-pitched (eg spam of two sides of. This is naturally equal to the total number of armature slots divided by the number of poles in the machine. 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. Short-pitch windings have a coil pitch of less than 1, which means the coil span is shorter than. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2. 086 Wb, what will be the values of the emfs? phase and line? I need the procedure to get to that answer. 160 degrees b. When 40V DC voltage is applied to a single-phase AC motor, it draws 1A current. The winding is 5/6 pitch. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. 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. Question. It may be the full pitched or short pitch. 2. Each of these coil spans is five slots, so this choice of winding. winding is fractional-pitched. ∙ 10y ago. It is always equal to 180° electrical. Obtain a coil span of 180 degrees (electrical) b. B = 10 sin theta + 2 sin 3 theta kilo-gauss, when theta is measured from the neutral axis. 12 Wb and a 20% 3 rd harmonics. On the other hand, if its span is less than a pole-pitch. Download these Free Coil Span or Coil Pitch MCQ Quiz Pdf and prepare for your upcoming exams Like Banking, SSC, Railway, UPSC, State PSC. 2. A 144-slot stator has a whole coiled 12-pole three-phase winding. (a) multiplex (b) fractional-pitch (c) full-pitch (d) pole-pitch 3. e. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. Learn what a pole pitch is, the pole pitch formula & definition, and how to. m. Wiki User. (d)Find the number of turns per phase, Tph. 1. Back Pitch Question 2: A 36-slot, 4-pole, dc machine has a simplex lap winding with two conductors per slot. 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). On the other hand, if its span is less than a pole-pitch. 👉 (2008-2018) With solution, BRANCH Wise Click the Link-ELECTRICAL. Coil–span or coil-pitch. a. 5 c) 18 d) 6 View Answer. When the parallel path is twice the number of poles then it is known as Duplex Lap Winding. 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 . 1. The coil used in double layer winding are diamond shaped as in the dc windings. of consecu- tive turns (c) distribute the winding. Publisher: PEARSON. 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. the distance between the two sides of coil is called the coil-pitch. Each phase in this case consists of four coils (two per slot). of slots/pole/phase, m = 4 ma 2x30 ata Soest 0-9659 (Ans. A=2, B=1 and C=2 and D=5. ∴ e = E 1 + E 2 = 2E. Let us assume that, a coil is short pitched by an angle α (electrical degree). 6. Last edited by markadlerdallas. A Three-phase four-pole AC machine has 60 coils in the stator and each coil has 100 turns. 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. 11. The coil span is 150°. Coil Span Factor: In a full pitch winding the coil span or coil pitch is always equal to the pole pitch which is equal to 180 electrical degrees. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. is known as coil span. air. 06 weber distributed sinusoidally over the pole. Comparator. It is usually measured in terms of teeth, slots or electrical degrees. In this case, there is a phase difference between the e. 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. 0. e. 951, 0. 1993) Example 37. If the span of the coil is reduced by an angle 'α' of electrical, then the. 15. c. P. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2 coil sides per slot. a coil. The winding is double-layer. It is using an armature winding which is short pitched by one slot. 707 B. Coil–span or coil-pitch. 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. 10. 4 pole = 90º. The back pitch and front pitch adopted could be respectively. ( c) 96 stator slots, six-poles, coil spans 1 to 13. BUY Delmar's Standard Textbook Of ElectricityThe slots per pole per phase are 8 and the coil span is 20 slots. 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. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. is known as coil span. Show transcribed image text There are 3 steps to solve this one. The pitch factor [3], [6], [7], [8] is the ratio of coil voltages for a fractional-pitch winding to those for a full-pitch one. The flux per pole is 0. 9659When the coil span is lower than pole pitch, the phasor sum of conductor voltages is less than the arithmetic sum, because of vector addition. Figure below shows a short pitched coil. can never be equal to pole pitch D. Front pitch (Y f):. 1K 39K views 2 years ago AC Electrical Machines Jimit Tutorials In this video basic terminologies related to AC armature winding like coil, conductor, coil side, front pitch,. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. 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. 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. 9 slots . It is usually measured in terms of teeth, slots or electrical degrees. The conductor being situated at the place of maximum flux density will have maximum emf induced in it. An alternator having 10-poles, 3-phase, and 60 Hz has 8 conductors per slot in single layer arrangement with 4 slots/pole/phase. 0. Every coil is connected to the commutator. pole pitch. Winding pitch is the coil span divided by the pole pitch, e. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. 2 are short-pitched, full-pitched and over-pitched coils respectively. Determine the equation for the emf induced in one turn, and its RMS value. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. • Coil span is nothing but the spacing between the two coil sides of a coil. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. Calculate the emf generated in each phase when the machine runs at 375 rpmHence, pitch factor or coil span factor K p = Cos(/2). must be exactly equal to pole pitch C. Figure 8 compares computed waveforms of phase back emf. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. 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. 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. What is the flux per pole if the voltage on open circuit is 1. 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. Calculate the pitch for the given windings: (i) 36 stator slots, 4 poles, coil span 1 to 8 (ii) 72 stator slots, 6 poles, coil span 1 to 10 (iii) 96 stator slots, 6 poles, coil span 1 to 12;. F. The coil span or coil pitch for short or fractional pitch coil is less than 180 electrical degree. 25 slots. 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. If the maximum flux per pole, with a sinusoidal distribution, is 0. Short-pitched coils are deliberately used because of the following advantages: 1. The distribution of upper-side voltage phasors is the same as that of coil voltage phasors,. 2 sin 30+0.