It is defined as the angular distance between the central line of one pole to the central line of the next pole. A three phase, 50 Hz, 8 pole alternator has a star connected winding with 120 slots and 6 conductor per slot. Q: Explain the following Armature Winding Terminologies (i) Coil Span (ii) Resultant Pitch A: In the following section, coil span and resultant pitch related to armature winding technology has… Q: Assume that a four-pole de machine has an armature with a radius of 15 cm and an effective length of…In the second example, with a pole pitch of 15. The length of the mean turn depends on the following factors (i) Gross length of the stator core: Each turn consists of two times the gross length of stator core. The pitch of the coil has 4 slots less than the pole pitch. 4. Question. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. 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. It is using an armature winding which is short pitched by one slot. 163Wb. Distribute the winding uniformly under different poles d. 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. How many comparators does a 339 IC contains? 4. The part of the coil in which EMF is generated is known as _____. Slots/pole/ph = m = 72/ (8×3) = 3. They are two basic physical types for the windings. The term "region" is important, because a design with 3 slots per pole and phase, for instance, can only be pitched 6/9 or 7/9 or 8/9. If the machine gives 3300 V between lines on open circuit with sinusoidal flux distribution. Lap and Wave winding are explained. Pole – pitch. e. 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. 0. Determine the generated. This problem has been solved! You'll get a detailed solution from a subject matter expert that helps you learn core concepts. Get Coil Span or Coil Pitch Multiple Choice Questions (MCQ Quiz) with answers and detailed solutions. Alternator connections: star or delta connections of alternators suppress triplen harmonics from appearing across the lines 1. 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 phase spread is 60° and the flux per pole is 25-8 x 10 weber. 4. Thus the total emf at the coil terminal A & B is the phasor sum of (E 1 +E 10), (E. c. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span), by the number of slots per pole. The coil span is 150°. in the two sides of the coil. 3 mWb and the total number of armature conductors is 1000. How do you calculate winding pitch? Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span) , by the number of slots per pole. For making coil span equal to a pole pitch in the armature winding of a d. In a 4 pole, 3 phase alternator, armature has 36 slots. Study with Quizlet and memorize flashcards containing terms like A lap winding, Twice, Full-pitch and more. 14. Coil Span Factor - Coil Span Factor is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them. It is usually measured in terms of teeth, slots or electrical degrees. If the angular distances between the two coil sides are less than one pole pitch, it is termed short pitch or fractional pitch coil. 9: Rated speed (rpm) 170: Rated current (Arms) 3. The Separation between the top and bottom sides of a coil is known as back pitch and is represented by (Y b). the distance between the two sides of coil is called the coil-pitch. Short Pitch Coil. . is known as coil span. The coil-span is 144° (electrical). Hence, the pitch factor or the coil span factor for the n th harmonic is given by, kcn = cos nα 2. Use: (Y) =) 2. The current is in same direction in both the sides of the coil. Generally. ∙ 10y ago. pole pitch = 180 electrical degrees or π electrical radians. In this case, there is a phase difference between the e. 16 wb/pole and is distributed sinusoidally over the pole. For making coil span equal to a pole pitch in the armature winding of a dc generator, the back pitch of the winding must equal the number of – Commutator bars per pole. pole pitch5. Commutator pitch. The coil span is 150 electrical degrees. In an alternator, for a coil having a span of 2/3 of pole pitch,. 1-9 coil span A SIMPLE explanation of what a pole pitch is in a generator or rotating machine. Calculate the distribution factor for a single layer 36 slots 2-pole three-phase stator winding. (ii) Pole pitch: The over hang portion of the coils depend upon the coil. It may be the full pitched or short pitch. Pole pitch is always equal to 180o electrical. 86 O 119. 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. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. 6. Register to editPitch factor problem. 0 D. 26. c. Thus, the total. . 50 Q 1. Give the values of front pitch, back-pitch and commutator pitch. The coil pitch is 12/15. are e. 10 such that two slots No. Generators 897 winding is fractional-pitched. . 1 is connected to coil side in slot No. Here ξ is the chorded angle or short pitch angle. m. 36 stator slots, 4-pole, coil span 1to 8 ii. When the coil is having a span of less than 180° electrical, it is known as a short-pitch coil. To understand, it simply means that one parallel path is in N-Pole and another parallel path in S-pole. 967. I need answer within 20 minutes please please with my best wishes. 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. Step by step Solved in 2. . Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. If fractional pitch is used, the emfs in the two coil sides are out of phase, which reduces the emf. A. 6. Identify number of rotor slots, number conductors / slot, coil span, number of slots per pole. It is always 180° electrical. 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. Its value is always less than unity. Each of these coil spans is five slots, so this choice of winding. In a synchronous generator, what do fractional pitch and fractional slot windings mean?• (e) The coil span must be odd integer. Answer: 0. This lecture will discuss;1. 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. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. arrow_forward. To improve the wave form only 80% of the pole pitch is wound. 1 times the pole arc. 11. Determine the equation for the. The electrical space angle between the active coil length or coil side is equal to one pole pitch. F. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. A 4-pole, 50 Hz alternator has double layer winding with 10 turns per coil and number of slots are 60. m. is known as coil span. 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. Calculate its coil span factor. Assuming double turn coil, Calculate the back pitch for progressive and retrogressive winding. In a 4-pole, 35 slot d. 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. 6 Pole pitch Coil span y=Z/2P + 1, y=Z/2P - 1 7 Conditions of P/C ϵ N, meaning P cannot be 1 and for three phase C/m N symmetry Single layer fractional slot winding with Z=30, and 2P=4 q 2 1 or q 5 D. (c)Find the number of coils in a coil group, m. In this case, there is a phase difference between the e. A coil is said to be fully pitched when the coil span is made equal to the pole pitch of the machine. 1 . DARWIN M. The skew factor reflects the flux reduction if the winding is angularly twisted along the axis. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched coil. F = 0. Robert L. Assuming single turn coil, calculate the back pitch for progressive and retrogressive winding. Pole pitch is always equal to 180o. three factors: the pitch factor (also called chording or coil-span factor), the distribution factor (also called breadth, spread or zone factor) and the skew factor. 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. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. The winding is wye-connected. The formula for pitch factor is given by The pitch factor in the above equation is for fundamental component of emf. 339 IC function as. Pole – pitch. kp: 0. 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. Short-pitched coils are deliberately used because of the following advantages: 1. ISBN: 9780133923605. Learn what a pole pitch is, the pole pitch formula & definition, and how to. 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. Figure 1. 772 x 10-3 Wb. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. What is a coil span? The coil span is the distance between one conductor of a certain phase and the corresponding return conductor. e. The armature windings conduct AC even on DC machines, due to the commutator action (which. It is one pole pitch. Determine the phase andline values of emf if the machine runs at 600 rpm and the flux per poleis 0. For making coil span equal to a pole pitch in the armature winding of a dc generator, the back pitch of the winding must equal the number of – Commutator bars per pole. A: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. Let us assume that, a coil is short pitched by an angle α (electrical degree). The alternator has 18 slots per pole and the first coil lies in slots 1 and 16. y=Coil span τ=Z/2P is the Pole pitch or full span II. The coil span is 150°. 0. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. See moreIf the coil span is less than the pole pitch then the coil is said to be a short-pitched coil. 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. A six pole, three phase alternator has 72 slots and a coil span of 1 to 10, is the pitch factor? A. Show transcribed image text There are 3 steps to solve this one. K p = cos (nα/2) Where n is the nth harmonic. Download Solution PDF. 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. The pole arc should be about 70% of pole pitch and length of core about 1. e. On the other hand, if its span is less than a pole-pitch. Emf induced per coil side is E. 5. e. Coil Span or Coil pitch. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. 1. Coil-span or Coil pitch (Y s) It is the distance, measured in terms of armature slots (or armature conductors) between two sides of a coil. The pole pitch is 35cm, the core length is 32cm & sta- 4th tor coil span is of pole pitch. a. 2. If the maximum flux per pole, with a sinusoidal distribution, is 0. Then, the pitch factor will be equal. per Phase: Part 1In this video, I'll give you an idea how to derive the fundamental pitch factor (coil span f. less than 180° electrical, the coils are called, short pitched coils or fractional pitched coils. electrical degrees indicate the amount the currents in conductors has changed. 10. Answer: c Explanation: K p =cosε/2 (i) Slots per pole = 36/4=9, for a coil span of 8 slots, the coil is short pitched by 1 slot and the chording angle is ε=γ = 20° ⇒ K p =cos10°=0. 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. 9; 21. 966 D. 4. The rotor is a large electromagnet. Then the coil span value is _____. c. Download these Free Coil Span or Coil Pitch MCQ Quiz Pdf and prepare for your upcoming exams Like Banking, SSC, Railway, UPSC, State PSC. is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. 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. 05 Wb, sinusoidally distributed. In this case, there is a phase difference between the e. m. Pitch Factor or Coil Pitch. The separation between the top and bottom sides of a coil is called Coil span. . A full-pitch coil is one whose pitch is equal to the pole-pitch at the working harmonic. slots. Use a diagram like that shown in fig. of a 10-pole three-phase 50Hz alternator with 2 slots per pole per phase and 4 conductors. In this study, the electromagnetic performances of dual 3-phase permanent magnet (PM) machines with coil span of two slot-pitches are comparatively investigated. Determine the phase andline values of emf if the machine runs at 600 rpm and the flux per poleis 0. 15 Consider the armature conductor marked X in Fig 1. fs. m. 6. It is always equal to 180° electrical. Full pitch winding. It. (b) Determine the pitch (or coil span) factors for the following windings: i. Pole pitch is the electrical angle between the north pole and. 0. Hence E. A. Obtain a full-pitch winding. A 4-pole, 50-Hz, star-connected alternator has 15 slots per pole and each slot has 10 conductors. If the maximum flux per pole, with a sinusoidal distribution, is 0. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch. In SWAT-EM we can set the coil span explicite. Find the EMF produced by a DC generator connected to a 6 poles coil rotating at 1200 RPM. At this situation, two opposite sides of the coil lie under two opposite poles. 924 359. K pn = cos nα/2. e. Emf induced per coil side is E. It may be the full pitched or short pitch. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. It has key variables such as Pole Pitch (back and front pitch, resultant pitch and communicator pitch, Coil Span, Commutator Pitch. in. a coil. The arithmetic sum of induced emfs is 2E. Introductory Circuit Analysis (13th Edition) 13th Edition. 14. Corresponds to 180/12 i. The pole pitch is 10 slots, and the coil pitch is 9 slots. $$\mathrm{Slot\:per\:pole =\frac{90}{6}= 15}$$ For a full-pitch coil, the coil span is 15 slots. A Three-phase four-pole AC machine has 60 coils in the stator and each coil has 100 turns. e. With a full-pitch coil, the emfs induced in the two coil sides are. There are 4conductors per slot and a sinusoidally distributed flux per pole of 36mWb. fs. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. P˚ = Pitch = coil span in no. The fundamental flux per pole is 0. You can read more about Full Pitch and Short Pitch Winding at:. Coil pitch: The distance measured in terms of armature slots or armature conductors between two sides of a coilQuiz # Solve the following problems. f. Y-connected alternator has 9 slots per pole and a full-pitch. The skew by one slot pitch gives the value of fundamental skew factor of 0. A. 1. It is using an armature winding which is short pitched by one slot. , angle between the two sides of. Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. , or 5/6 × 180° = 150 electrical degrees. Here, e = E 1 = E 2 = E. 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. 125 Wb and a. p. coil pitch in terms of slots4. Coil – span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 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. IV. The distance between the two sides of an individual coil of and AC armature winding id termed the coil pitch. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 958] (B) Determine the maximum flux per'pole when connected to a' 220-volt,60-cycle line, neglecting local resistance and reactance drops. Figure 8 compares computed waveforms of phase back emf. o5Wb. Coil Span (ii) Resultant Pitch. Please see Electrical 4 U site for article on Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. The flux per pole has a fundamental component of 0. The slots per pole per phase are 8 and the coil span is 20 slots. in the two sides of the coil. ISBN: 9780073373843. m. This is shown in the figure to left. A pole pitch is always 180° electrical regardless of the number of poles on the machine. three factors: the pitch factor (also called chording or coil-span factor), the distribution factor (also called breadth, spread or zone factor) and the skew factor. The winding calculator allows you to find the optimum winding layout for your electric motor in a fast and convenient way. First. 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. m. 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. The coil span should be minimum of about 8. Figure 4 shows the flux distribution linked to a short-pitch coil. The stator of a synchronous machine is such that:3-phase; 4 poles; 36 slots; winding double-layered; 2 slots short pitched and 2-turn for each single coil. 0. Key. 3- Determine the coil span for 3-phase, two pole alternator, the pole pitch is equal to 18 slots and the coil span factor is. are e. situation, two opposite sides of the coil lie under two opposite poles. 956, 0,647 02A pole pitch covers 25/4 = 6. In the considered motor, the fundamental winding factor is equal to the skew factor due to unity fundamental coil-span and distribution factors. Electrical Engineering questions and answers. e. ∴ e = E 1 + E 2 = 2E. What is meant by a full pitch winding a fractional pitch winding? If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. Coil Span: It is the angular distance between the two sides of the coil. In SWAT-EM we can set the coil span explicite. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . 911 V B. Coil spanA: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. 086 Wb, what will be the values of the emfs? phase and line? I need the procedure to get to that answer. There. m. 0. 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 ____________. . Result- ant flux in the air-gap is 5 ´ 10– 2 webers per pole sinusoidally distributed. An alternator having 10-poles, 3-phase, and 60 Hz has 8 conductors per slot in single layer arrangement with 4 slots/pole/phase. 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. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. • Coil span is nothing but the spacing between the two coil sides of a coil. This distance is measured in terms of armature slots or armature conductors that come between two. 9 and the efficiency is 0. A. It may be the full pitched or short pitch. The coil span is 160°. 86 O 119. It is lesser than the value in the first case. 135 degrees d. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. 2. . The pitch factor of an alternator is a measure of the winding distribution along the armature. . However in practise this often isn’t the best choise because of the high harmonic content. 15. 3 percent. Coil–span or coil-pitch. CONTENTS CONTENTS + 0 ) 2 6 - 4 Lear ningPole – pitch. 1. Distribute the winding uniformly under different poles d. 7. Each of these coil spans is five slots, so this choice of winding pattern is referred to as “Five-Sixths” pitch. β = 180o/ = 20o. 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. m. what is coil pitch or coil span. In a full pitch coil, the coil span will be 180° electrical (equal to pole pitch). Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . m. 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. 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. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. A. Solution for Calculate the pitch factor for the following windings: a) 72 stator slots, 6 pole, coil span 1 to 10. 0 C.