This is shown in the figure to left. . Calculate the sinusoidally distributed flux per pole required to give a line voltage of 11 kV on open circuit, and the full. Note. (a) commutator bars per pole (b) winding elements (c) armature conductors per path (d) armature parallel paths. To get a coil around every tooth, we need two winding layers (double layer winding). For example if S/P = 10. Determine the phase andline values of emf if the machine runs at 600 rpm and the flux per poleis 0. e. Calculate the sinusoidally distributed flux per pole required to give a line voltage of 11 kV on open circuit, and the full load current per conductor. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. ∴ Coil span factor, Where β is the angle through which the coil is short pitched. The coil span A. belt factor. 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. In this case, the coil sides lie under opposite poles, hence the induced e. 1 times the pole arc. A. The coil span is 160°. Wheres is the number of slots, and 2p is the number of poles [19]. 10. Calculate the RMS value of the induced emf per phase. Each phase in this case consists of four coils (two per slot). A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. 1822 V C. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. The winding is double-layer. situation, two opposite sides of the coil lie under two opposite poles. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. 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. Draw the developed diagram andshow the positions of brushes. It is expressed in terms of number of slots per pole. BUY Delmar's Standard Textbook Of ElectricityThe slots per pole per phase are 8 and the coil span is 20 slots. Better emf waveform in case of generators 6. There are 4conductors per slot and a sinusoidally distributed flux per pole of 36mWb. The coil span of the alternator is 1 to 8. 100+ Subjects. Determine the generated. The distribution of upper-side voltage phasors is the same as that of coil voltage phasors,. The winding is wye-connected. (5/6) of a pole pitch. Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding. Power System Analysis and Design (MindTap Course List) 6th Edition. If the coil span is exactly equal to the pole-pitch, then such a coil is called a full-pitch coil. Assuming double turn coil, Calculate the back pitch for progressive and retrogressive winding. 06 weber distributed sinusoidally over the pole. Calculation: Given that, Slots S = 72. of slots per pole = 15 but coil span is… Q: A synchronous generator has 9 slots per pole. Let us assume that, a coil is short pitched by an angle α (electrical degree). 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 . It is usually measured in terms of teeth, slots or electrical degrees. 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. 015 Wb. 31. Give the values of front pitch, back-pitch and commutator pitch. . It may be the full pitched or short pitch. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched coil. However, the coil span may be less than a pole pitch, in which case the coil is described as short pitched or chorded. Pole pitch is the electrical angle between the north pole and. 50 Q… A: Find the coil span Fractional pitch winding = 8/14 Q: For alternator having fractional pitch winding of 10/15 the coil span is O 2. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. 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. it is defined as the peripheral distance between the center of two adjacent poles in a DC machine. What is a coil span? The coil span is the distance between one conductor of a certain phase and the corresponding return conductor. Looking at the diagram in the question. what is coil pitch or coil span. Step by step Solved in 4. It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. Wheres is the number of slots, and 2p is the number of poles [19]. The coil span is 150°. ) Given: 120 slots, ,10 poles, double layer winding, coil pitch is shorted by 2 slots, f=60 Hz, Y connected. ’s of consecutive turns c. If the coil span of a single coil is less than the pole pitch of 180° electrical, i. When a coil. 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). coil pitch in terms of electrical angle3. 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. Pole Pitch: It is the angular distance between the two adjacent poles. 85. frame. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. Copy. The pole pitch is 35 cm. Then, the pitch factor will be equal. 2-pole star-connected, armature winding of a generator has 6 slots per phase. The flux per pole has a fundamental component of 0. Hence, the total e. Pole – pitch. 0 B. 2. (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 . 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. Calculate the pitch factor for: (i) Fundamental (ii) 3 rd harmonic (iii. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. Pole and slot numbers. If each coil is short pitched by an angle of 36 ∘ electrical. 10 such that two slots No. Not ( I want a solution within 20 minutes. c. Let E 1, E 2 and E R be the emf induced in coil side lying under North Pole, South Pole and resultant of emf generated in both the active lengths of coil. Q2: For a 3-phase winding with 3 slots per pole per phase and coil span of 8 slots, compute the distribution and pitch factor for fundamental and 3 rd harmonics. This. none of the aboveThe coil span generally varies from 2/3 pole pitch to full pole pitch. 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). 7. In an alternator, for a coil having a span of 2/3 of pole pitch,. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. Pole pitch is always equal to 180o 7. Each of these coil spans is five slots, so this choice of winding pattern is referred to as “Five-Sixths” pitch. p. 2. 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. When coil sides are pole pitch apart, the DC armature winding is called as _____ a) Multiplex b) Fractional-pitch c) Full-pitch d) Pole-pitch View Answer. 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. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. p. Better emf waveform in case of generators 6. Coil span or Coil Pitch. The winding is wye-connected. If the machine gives 3300 V between lines on open circuit with sinusoidal flux distribution. 0. arrow_forward. 6. The flux per pole has a fundamental component of 0. 60 hz, 10-pole alternator has 120 slots and 4 turns in every coil. , Y = 2/3 τ p. 15. A pole pitch is always 180° electrical regardless of the number of poles on the machine. Then, the pitch factor will be equal. 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 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. The winding spans all11. m. . 7. In a short pitch coil, the coil span will be (180 -. α = Angle of short pitch = 20o. m. It means that coil span is 180 electrical degrees. 951, 0. For a simplex lap winding, the commutator pitch YC = 1 and coil span YS ~ pole pitch. Number of empty slots = 18 – 15 = 3 slots ( herefore alpha = 180^circ imes frac{3}{{18}} = 30^circ). coil pitch in terms of electrical angle3. 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. We must note that the coil-pitch and flux barriers of the NC2 are adjusted as shown in. 24 where pole- pitch of 4 has been assumed), then winding is called full-pitched. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. If the coil span is equal to the Pole pitch then it is called a full pitch coil. Obtain a full-pitch winding. g. 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. Obtain a coil span of 180 degrees (electrical) b. Understand what Full Pitch and Short Pitch Windings are, and what Coil Span is. It is usually measured in terms of teeth, slots or electrical degrees. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. m. ISBN: 9780073373843. Calculate its coil span factor. Coil span is the number of slots between the two sides of the same coil. 5. 60o / 90o = 2/3. 5, then the coil-span can be either 11 or 10 slots. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . Please see Electrical 4 U site for article on Armature Windings: Pole Pitch, Coil Span And Commutator Pitch. The pole pitch is always 180 degrees electrical regardless of the number of poles in a machine. 7. m. 24 B where coil pitch is 3/4th of the pole pitch), then the D. A 144-slot stator has a whole coiled 12-pole three-phase winding. 10 A three-phase, wye-connected alternator has 15 slots/pole. 911 V B. The coil is also short-pitched (eg spam of two sides of. For alternator having fractional pitch winding of 8/14 the coil span is 102. fs. 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. If we used short pitched winding for armature winding than pitched factor is included in EMF equation in Alternator. Number of Commutator Segments - Number of Commutator Segments is the count of cylindrical assembly of insulated segments that are mounted on the shaft. 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). MMF OF ARMATURE A. 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. Here, e = E 1 = E 2 = E. 2 sin 50 +0. 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 coils cannot be full - pitched; they may be short - pitched with 15 slots, or long - pitched with 16 slots. 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. Slots/pole/ph = m = 72/ (8×3) = 3. The winding is 5/6 pitch. 966The pole pitch, mQ ′ ∕ p, is also fractional, so that the coil-span cannot be of full-pitch. The pole pitch is 10 slots, and the coil pitch is 9 slots. The rotor is a large electromagnet. 3 mWb and the total number of armature conductors is 1000. Publisher: PEARSON. Based on the prototype of the long stator LSM we designed, the effect of different short-pitch factors on the propulsive force was studied: (8) {y p θ = τ π k y = sin θ 2 where y p is the short pitch, denoted by length; θ is the short pitch angle (rad. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Figure below shows a short pitched coil. 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. Assume that the coil span is 150° electrical. Download Solution PDF. The armature windings conduct AC even on DC machines, due to the commutator action (which. P. In this study, the electromagnetic performances of dual 3-phase permanent magnet (PM) machines with coil span of two slot-pitches are comparatively investigated. A six pole, three phase AC generator has 72 slots, the coil span is 12. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. In a short pitch coil, the coil span will be (180 – α)° electrical ( α = angle by which coils are short-pitched and always less than pole pitch ). What is the coil span for a 2 pole 18 slot machine? a) 9 b) 4. The induced emf in each coil side. The commutation is improved in short-pitched coil, but the emf induced will be less compared to full-pitch. 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. N st 2p r; 12 14 16 18 20 22; 12:. In a 4-pole, 35 slot d. The pitch factor of an alternator is a measure of the winding distribution along the armature. C machines short pitch winding is generally used to reduce harmonic and. round the coil which is the vector sum of e. How many comparators does a 339 IC contains? 4. . B = 10 sin theta + 2 sin 3 theta kilo-gauss, when theta is measured from the neutral axis. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. If the coil. Pole arc/ pole pitch = core length/ pole pitch = 0. I need answer within 20 minutes please please with my best wishes. 4. Transcribed Image Text: (d) obtain a full-pitch winding. Since the winding is full pitched coil, so the pitch of each. The pitch of the coil is 2 slot less than the pole pitch. ∴ e = E 1 + E 2 = 2E. 0 C. Coils 1, 2 and 3 shown in Fig. m. , Y R = Y B − Y F . Define Pitch Factor /Distribution Factor and present the formula to calculate. In the considered motor, the fundamental winding factor is equal to the skew factor due to unity fundamental coil-span and distribution factors. 6. are e. Use: (Y) =) 2. 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. d5. 23. is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. 14. 956, 0,647 02A pole pitch covers 25/4 = 6. 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. p. Pitch Factor is calculated by dividing the coil throw (–) 1 (coil span), by the number of slots per pole. 6 turns. When the coil is having a span of less than 180° electrical, it is known as a short-pitch coil. BUY. (8) A SIMPLE explanation of Full Pitch and Short Pitch Winding. Por a full-pitch coil, Kr = I (unity) r:or a fractional-pitch coil, Kr < 1 6. 9659. 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 usually measured in terms of teeth, slots or electrical degrees. Coil Span: It is the angular distance between the two sides of the coil. , coil span is 180º electrical) is called a full-pitch coil. If the coil span is less then one pole pitch than it is called short pitch coil. 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. in the two sides of the coil. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° = 0. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. In this. Pole – pitch. M. 10 slots d. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. The spacing is expressed in terms of number of slots between the sides. 1993) Example 37. 967. 4, Fig. Pole pitch is always equal to 180o. Pole pitch is the mechanical angle between adjacent poles, e. fs. 1. 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. CONTENTS CONTENTS + 0 ) 2 6 - 4 Lear ningPole – pitch. 4. Hence, the pole pitch of that DC machine would be 24. coil pitch in terms of slots4. 1kv. e. b. 15 Consider the armature conductor marked X in Fig 1. is known as coil span. 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. In this video lecture you will learn about electrical angle,mechani. e. A coil whose sides are separated by one pole pitch (i. A=2, B=1 and C=2 and D=5. Short Pitch Coil. of slots per pole = 2 = 6 saree tensed gOSeaee Slot pitch, a = oF slow/pole > No. Calculation:When the coil sides forming a coil are spaced exactly one pole pitch a part they are said to be of full-pitch. Display and compare winding harmonicsElectrical Engineering. Allow 10 ampere for the field current and assume a voltage drop of 4 volts for the armature circuit. fs. Coil – span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. 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. 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. Its value is always less than unity. On the other hand, if its span is less than a pole-pitch. The usefulness of winding distribution and chording in reducing or eliminating harmonics will be touched on in. Each of these coil spans is five slots, so this choice of winding. This type of winding is mainly used for. 11. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. Download Solution PDF. Lap winding • Suppose we want to make a lap winding for a P = 4 pole D. It is also called a chorded coil. This advancement is measured in terms of armature conductors and is called back pitch. The primary reason for making the coil span of a d. number of slots and a coil span of two slots require at least 18 slots. 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. The first coil lies in slots 1 and 16. In a 4-pole, 35 slot d. The flux distribution curve of a smooth - core 50 c/s generator is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. An 8-pole lap wound DC generator has 120 slots having 4 conductors per slot. The slots per pole per phase are 8 and the coil span is 20 slots. 1 the coil span should be approximately equal to a pole pitch. It equals pole pitch = Z P . 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. 259 C. 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. However in practise this often isn’t the best choise because of the high harmonic content. It is expressed in terms of electrical space degree. Q3- A/ 10 MVA, 11 KV, 50 Hz, 3-phase star-connected alternator s driven at 300 RPM. 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. 3. If the coil span is equal to the Pole pitch then it is called a full pitch coil. If the coil span is equal to the Pole pitch then it is called a full pitch coil. Author: Frank D. (d)Find the number of turns per phase, Tph. Use a diagram like that shown in fig. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. Kr ==sink 2 · Kp =pitch factor in dcci111al p" =span of the coil in electrical degrees. A 4 pole, 12 slot lap wound dc armature has two coil side/slot. The coil-span chosen is of course less than the full-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). In practice, coil pitch (or Span) as low as eight-tenths of a Pole Pitch, is employed without much serious reduction in emf. 2 Selecting the coil span for a given pole pitch. Every coil is connected to the commutator. 6A. Problem 1 : Develop the layout of a lap winding for a 3 phase ac machine having 4 pole and 24 slots. 75), the lowest 2-solt coil span. Two-and four-pole rotors have normally nonsalient poles, while rotors with more than four poles have salient poles. Step by step Solved in 2. 2. Coil spanA: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. 339 IC function as. You can read more. (2006), “Distribution, coil-span and winding factors for PM. 772 x 10-3 Wb. For a full pitch coil, the value of pitch factor is unity whereas for its value is also unity for concentrated coils. If the coil. 165 degrees. The windings are arranged as 5 conductors per layer. In this. 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. When the. fs. c. 956 1. armature winding equal to a pole pitch is to (a) obtain a coil span of 180° (electrical) (b) ensure the addition of e. View full document. 9780133923605. Hence, the total e. The random wire placement leads to a wider distribution of resulting wire length on the coil body and consequently a wider range of electric coil resistances. Based on number of layers (i) Single layer. arrow_forward. It is always less than unity. If the coil span is equal to the Pole pitch then it is called a full pitch coil. The width of the coils is 5/6 of the pole pitch. It means that coil span is 180 electrical degrees. This lecture will discuss;1. Where it is called an over-pitched coil if the coil span is greater than the pole pitch. Since slot pitch is 6, 6 slots have upward arrows, 6 down and so on. The pole arc should be about 70% of pole pitch and length of core about 1. 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. 12 3-0. If the coil-pitch is one pole pitch, it is called the full-pitch coil. m. Coil span or coil pitch Ys: It is the distance between the two sides of a coil measured in terms of armature slots. 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. What is the flux per pole if the voltage on open circuit is 1. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers.