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 ____________. Register to editPitch factor problem. e. Coil Span: It is the angular distance between the two sides of the coil. Corresponds to 180/12 i. Coil span is simply a peripheral distance between two sides of a coil. A DC armature of a miniature motor (or generator) A partially-constructed DC armature, showing the (incomplete) windings In electrical engineering, the armature is the winding (or set of windings) of an electric machine which carries alternating current. ISBN: 9780133923605. 10 A three-phase, wye-connected alternator has 15 slots/pole. the coil will be in 180o. 0. arrow_forward. Coil–span or coil-pitch. Power System Analysis and Design (MindTap Course List) 6th Edition. 15. A 4-pole, 50-Hz, star-connected alternator has 15 slots per pole and each slot has 10 conductors. phase shift with emf induced in the other side of the coil. 8 slots b. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. 1, if the coil sides are placed in slots 1 and 7, then it is full-pitched. Step by step Solved in 2. SEE MORE TEXTBOOKS. (In general, Y C = ± m) 5. air. A 4-pole, 3-phase synchronous machine has 48 slots. 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. Comparator. Pole pitch is the mechanical angle between adjacent poles, e. The flux per pole has a fundamental component of 0. The reduction fraction is the pitch factor. Step by step Solved in 4. Concept: Coil pitch or coil span: It is defined as the angular distance between the two coil sides of one coil. . Commutator pitch of a progressive lap winding is yc = +1. (8) A SIMPLE explanation of Full Pitch and Short Pitch Winding. The arc diagram contains all the necessary information for connecting the pole-groups correctly. Here’s the best way to solve it. Let n be the number of slots per pole. Coil Span: The number of core slots spanned by the sides of the coil. ed = electrical degree Example 2: Calculate the pole pitch for a three phase 4 pole ac machine having 36 stator slots. It is expressed in terms of electrical space degree. Calculation:When the coil sides forming a coil are spaced exactly one pole pitch a part they are said to be of full-pitch. 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. 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. (16) k p1 = sin β 2 <1 where β is the coil span in °electrical, β=sα; s is the coil span in slots. 955, whilst the second option gives (k_{sk1}) equal to 0. . $$\mathrm{Slot\:per\:pole =\frac{90}{6}= 15}$$ For a full-pitch coil, the coil span is 15 slots. A 4 pole, 12 slot lap wound dc armature has two coil side/slot. ) Given: 120 slots, ,10 poles, double layer winding, coil pitch is shorted by 2 slots, f=60 Hz, Y connected. The winding is housed in 360 slots and has 6 conductors per slot, the coils spanning (5/6) of a pole pitch. 2. Fractional slot winding 6. Table of Contents Terms used in the armature winding Conductor Turn Coil Coil Side Front end and Back end connector Pole. The arithmetic sum of induced emfs is 2E. Calculate the emf generated in each phase when the machine runs at 375 rpmHence, pitch factor or coil span factor K p = Cos(/2). , coil span is 180º electrical) is called a full-pitch coil. 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. 3K views. (a) multiplex (b) fractional-pitch (c) full-pitch (d) pole-pitch 3. Note that although the span of a full-pitch coil is not an integer in a fractional-slot winding, the full-pitch coil is nevertheless an im- The correct answer is option 3. The 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 flux per pole has a fundamental component of 0. , Y = 2/3 τ p. α = Angle of short pitch = 20o. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. The use of windings with a coil span of two slots promises a better balance between ohmic losses and end windings space on the one hand and harmonic content. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. The Separation between the top and bottom sides of a coil is known as back pitch and is represented by (Y b). 06 weber distributed sinusoidally over the pole. Calculation: Given that,For making coil span equal to a pole pitch in the armature winding of a d. Pole–pitch: A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. A chording angle ε is defined as the angle by which coil span departs from _____ a) 90° electrical space degrees b) 180° electrical space degrees c) 360° electrical space degreesSolution: No. where: coil. per Phase: Part 1In this video, I'll give you an idea how to derive the fundamental pitch factor (coil span f. ; 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. pitch factorThe flux distribution Curve of a smooth-core 50 c/s generator is. β = 180o/ = 20o. Short-pitched coils are deliberately used because of the following advantages: 1. 6. On the other hand, if its span is less than a pole-pitch. arrow_forward. slots. Note. 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. . c. Fig. If the coil-pitch is one pole pitch, it is called the full-pitch coil. 1 times the pole arc. Normally the nearest whole number is selected which is 6 in present case. m. Determine the equation for the. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. 16 wb/pole and is distributed sinusoidally over the pole. On the other hand, if its span is less than a pole-pitch. M. in. Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding. In the considered motor, the fundamental winding factor is equal to the skew factor due to unity fundamental coil-span and distribution factors. the coil span is (180-ε), therefore the emf induced in these coil sides will also be separated by this angle. Muthu RE: How. This distance is measured in term of armature slots or armature conductor come between two adjacent pole centers. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. In such coils, the two coil sides are not under the poles. Relation between frequency, speed and number of poles: Fig: 1. A 144-slot stator has a whole coiled 12-pole three-phase winding. 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. 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. Find the breadth factor for 3-Iwinding with 2 slots per pole per phase. If the coil span is equal to the Pole pitch then it is called a full pitch coil. Similarly, for a coil having a span of 2/3 pole-pitch, kc = cos 60°/2 = cos 30° =. Duplex Lap Winding. Determine the phase and line voltages if the coil is full pitched. 9 slots . When the parallel path is twice the number of poles then it is known as Duplex Lap Winding. 79. Pole and slot numbers. 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. Display and compare winding harmonicsElectrical Engineering. 9780133923605. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. In a 4 pole, 54 slot dc armature, calculate the coil span. Pole pitch is always equal to 180o electrical. The value of α will usually be given in the question, if not, then assume kc = 1. Chording: with coil-span less than pole pitch 5. 4. In a 4-pole, 35 slot d. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. 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. 951, 0. armature winding equal to a pole pitch is to (a) obtain a coil span of 180° (electrical) (b) ensure the addition of e. 4 Winding Factor Both distribution factor (Kd) and pitch factor Kp together is known as winding factor Kw. 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. 98: 61. Looking at the diagram in the question. The armature has double layers winding. There are 4conductors per slot and a sinusoidally distributed flux per pole of 36mWb. • Coil span is nothing but the spacing between the two coil sides of a coil. 0. Petruzella. This problem has been solved! You'll get a detailed solution from a subject matter expert that helps you learn core concepts. 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. Hence, the pole pitch of that DC machine would be 24. 3, Fig. Winding table. Armature Currents and MMF of 5-Phase Machine The armature currents of 5-phase machine can be expressed with formula (1). C. The pitch factor, in rotating electrical machinery, is defined as the ratio of resultant EMF of a _____ a) full-pitched coil to that of a chorded coil b) full-pitched coil to the phase EMF c) chorded coil to the phase EMF d) chorded coil to that of a full-pitched coil View AnswerCalculate the pitch factor for an alternator winding with 36 slots, 4 poles, and coil span of 1 to 8. 2. You can read more about Full Pitch and Short Pitch Winding at:. Discuss the effect of making the coil span very different from the pole pitch on (a) the coil emf and (b) the coil torque. Result Number of. 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. 2. ) A 6-pole, 3-phase, 60-Hz alternator has 12 slots per pole and four conductors per slot. Fig. 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. Let us assume that, a coil is short pitched by an angle α (electrical degree). 0. 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. The coil pitch is 12/15. The winding is double-layer. 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. The value of α will usually be given in the question, if not, then assume kc = 1. The highest winding factor can be obtained with 4-solt span coil (the coil span is closest to pole pitch 3. c. b. m. 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. 15. Number of Commutator Segments - Number of Commutator Segments is the count of cylindrical assembly of insulated segments that are mounted on the shaft. The width of the coils is 5/6 of the pole pitch. In a 4-pole, 35 slot d. [8+8] 2. Wiki User. Boylestad. Coil Span: It is the angular distance between the two sides of the coil. The correct answer is option 2): 5 slots Concept: Coil span (also known as coil pitch) is defined as the peripheral distance between two sides of a coil, measured in terms of the number of armature slots between them. Let the coil have a pitch short by angle q electrical space degrees from full pitch and induced emf in each coil side be E. Table 1 lists suitable combinations of stator slots and rotor poles for six-phase windings and gives the corresponding number of slots per pole per phase q6~. The analyses of different six-pole winding configurations, obtained by changing the coil pitch number, winding layer, and stator slot number for the families of 0. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. Figure 2 illustrates a full pitch winding. K pn = cos nα/2. In a 4 pole, 3 phase alternator, armature has 36 slots. , coil span is 180º electrical) is called a full-pitch coil. 0 D. The flux per pole has a fundamental component of 0. 24 where pole- pitch of 4 has been assumed), then winding is called full-pitched. 2:. If the coil span factor is 0. We make the coil span less than 180 degrees electrical space degrees in a fractional pitch winding. Download Solution PDF. TERMS Coil Throw: The location in an armature core of the sides of a coil starting in slot number one (1). It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. C. phase shift with emf induced in the other side of the coil. A pole pitch is always 180 electrical degrees, regardless of the number of poles on the machine. g. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. P˚ Kp = sin [(90°)(pitch)] Kp = sin 𝟐 PROBLEM 1: A 6 pole, 3Φ AC generated has 72 slots, the coil span is 12. The coil span is 150°. If the machine gives 3300 V between lines on open circuit sinusoidal flux distribution, determine. 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. Determine both the winding factor and the effective turns per phase. e. In an alternator, for a coil having a span of 2/3 of pole pitch,. In this video lecture you will learn about electrical angle,mechani. 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. Calculate the pitch factor of the coil for 3 rd harmonic. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a. A) 1. Now coil is shorted by 1 slot i. It mainly focuses on two PM machines with different slot/pole number combinations (N s /2p), that is, the 24-slot/10-pole and 24-slot/14-pole machines (2p = N s /2 ± 2). It falls short by 1/6 pole-pitch or by 180°/6 = 30°. Coil span is defined as the peripheral distance between two sides of a coil. This lecture will discuss;1. Obtain a coil span of 180 degrees (electrical) b. 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. In this. Coil span or Coil Pitch. Pole pitch is always equal to 180o. The coils are made up of 8 turns, and the windings are double layer. 5. 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;. 2 Selecting the coil span for a given pole pitch. K P = resultant emf of short pitch coil/ resultant emf of full pitch coil = cos α/2. L = πD/p = πD/ = 43 x 24 = 1048 ( satisfactory) Ex. p Number of pole-pairs q Ratio of pole-width to pole-pitch Q Least number of slots in a doubly slotted machine Qs Number of coils per phase of distributed winding Ru Resistance of phase-belt, u = a,b,c R Matrix of branch resistances Sn Cross-sectional area of nth coil T Time-period vu Supply voltage of uth phase-belt, u = a,b,c α Mechanical. Problem. . Determine the pitch (or coil span) factors for the winding ,24 Stator slots ,4 poles, coil span 1 to 5 12. Where n is the nth harmonic. If the machine gives 3300 V between lines on open circuit with sinusoidal flux distribution. C. It. When two capacitors of reactances 10ohms and 20 ohms are connected in parallel across a 100 V supply, total VAR drawn will be _. Pitch factor. The flux per pole is 0. 125 Wb and a 25% third component. . Lap winding • Suppose we want to make a lap winding for a P = 4 pole D. Zoom In Zoom Out Reset image size. 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. They are two basic physical types for the windings. Coil span σ, winding factor k w, pole ratio G r and N c for possible pole-slot combinations in the proposed FMPM machine. 1, or nonsalient (flush with the surface of the rotor), as shown in Fig. 6. F induced in the other side of the coil. 26. It means that coil span is 180 electrical degrees. The coil span or coil pitch for short or fractional pitch coil is less than 180 electrical degrees. Pole pitch is the peripheral distance between two adjacent poles. 4. The pole pitch is always 180 degrees electrical regardless of the number of poles in a machine. Then the coil span value is _____. 7. The winding is 5/6 pitch. The. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Coil spanA: slot angle = 180slot per pole = 18015 = 12 pole pitch = no. arrow_forward How to calculate the pitch factor of a 8 pole alternator with an armature wound coils having 18 / 24 fractioanl pitch. The individual coils may have a span greater or less than a pole pitch but the average coil-span equals one pole-pitch. 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. After updating the table, the drop-down list below lets you select whether to display the number of slots per pole per phase, the maximum possible fundamental winding factor, the number of winding symmetries,. 13. For a 3-phase winding with 5 slots per pole per phase and with a coil span of 12 slot pitch, the value of pitch factor is. 0. 25 O 5. m. 966The pole pitch, mQ ′ ∕ p, is also fractional, so that the coil-span cannot be of full-pitch. Electrical Engineering. The windings are arranged as 5 conductors per layer. Calculate the no-load terminal voltage, if the speed of the alternator is 1500r. Pole Pitch: It is the angular distance between the two adjacent poles. g. Pole – pitch. 16. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2 coil sides per slot. . Pole pitch = 180 electrical degrees = S/P = 2C/P. 0 i D. ; Coil Span: It is the angular distance between the two sides of the coil. Number of empty slots = 18 – 15 = 3 slots ( herefore alpha = 180^circ imes frac{3}{{18}} = 30^circ). For n th harmonic. IMs designed by utilising the winding configurations given in Section 3 are analysed and both SS and FW performance characteristics are presented in Section 4. 10. The armature winding is housed in 360 stors with 6 conductors per slot. 14. e. Calculate its coil span factor. ( b) 42 stator slots, four-poles, coil spans 1 to 10. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. In this situation, two opposite sides of the coil lie under two opposite poles. † ‡ ˆ ‰ Š ‹ Œ Ž ‘ ’ “ ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿPitch factor: Full-pitched coils i. 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 is usually measured in terms of teeth, slots or electrical degrees. Assuming single turn coil, calculate the back pitch for progressive and retrogressive winding. the core length 32 cm, and the stator coil span four fifth of the pole pitch. A resultant air-gap flux of a 16-pole, 3-phase alternator is 0. The separation between the top and bottom sides of a coil is called Coil span. Coil span is 16 – 1 = 15 slots. Pole pitch = S/P. The part of the coil in which EMF is generated is known as _____. m. Give the values of front pitch, back-pitch and commutator pitch. ∴ e = E 1 + E 2 = 2E. IMs designed by utilising the winding configurations given in Section 3 are analysed and both SS and FW performance characteristics are presented. Solution for For alternator having fractional pitch winding of 10/14 the coil span is 4. 80The coil pitch of such distributed windings is normally at least three slots which brings about a high winding resistance and occupies much space for the end windings. Pole – pitch. In this case, the coil sides lie under opposite poles, hence the induced e. A 3-phase, 12-pole, star-connected alternator has 180 slots with 10conductors per slot and the conductors of each phase are connectedin series. For a coil span of 13/15 of a pole pitch, the phase winding factor is: K_p = cos(π * 13 / (2 * 15)) = 0. A coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below. As against this if coils are used in such a way that coil span is slightly less than a pole pitch i. 60 hz, 10-pole alternator has 120 slots and 4 turns in every coil. 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. If the coil span is. 40 O 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. c. in the two sides of the coil. C. The coil span is 150°. The pitch of the coils is 2 slots less than the pole pitch. When the winding is full pitched, coil span is equal to the pole pitch. When the coil span is less than 180 electrical degrees, the winding is called short pitched or fractional pitch or chorded winding as shown in Fig. Key. f. Figure 1. 259 C. For a short pitch coil KC. Coil–span or coil-pitch. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. e. (a)Find the total number of coil groups in the machine. a. I need answer within 20 minutes please please with my best wishes. 7. Pole – pitch. You can read more. 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. p. Allow 10 ampere for the field current and assume a voltage drop of 4 volts for the armature circuit. Since 1 pole pitch is the angular distance between the two. The meaning of FULL-PITCH WINDING is the winding of an armature in which the two sides of the armature coil span a distance equal to the pole pitch. fs. 6. 14. The coil span should be minimum of about 8. 2 are short-pitched, full-pitched and over-pitched coils respectively. Introductory Circuit Analysis (13th Edition) 13th Edition. When measured in electrical degrees one pole itch is equal to 1800. Author: Robert L. Winding pitch is the coil span divided by the pole pitch, e. The coils are place in 60 uniformly distributed slots around the inner perimeter of the stator. 26. To understand, it simply means that one parallel path is in N-Pole and another parallel path in S-pole. It may be the full pitched or short pitch. What is. 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. If the coil sides are placed in slots 1 and 6, then it is short-pitched or fractional-pitched because coil span is equal to 5/6 of a pole-pitch. Publisher: McGraw-Hill Education. in. 9 and the efficiency is 0. 966the coil span of the two slot‐pitch technique has been pro-posed, based on the ‘stator shifting’ concept [8, 9]. 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. Looking at the diagram in the question. Obtain a full-pitch winding. o5Wb. There’s just one step to solve this. , angle between the two sides of. In a 4 pole, 3 phase alternator, armature has 36 slots. 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). In this case, there is a phase difference between the e. If the coil pitch is less than one pole pitch, the coil is called the short-pitch coil or fractional-pitch coil. 4, Fig. In a 4 pole, 35 slot dc armature, calculate the coil span a. , or 5/6 × 180° = 150 electrical degrees. Figure 4 shows the flux distribution linked to a short-pitch coil. 11. m. 7 slots c. If the coil span is exactly equal to the pole-pitch, then such a coil is called a full-pitch coil. 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. 5 ≤ q ≤ 3, are presented in Section 3. Thus coil span of either 6 or 7 may be selected. The usefulness of winding distribution and chording in reducing or eliminating harmonics will be touched on in. (Assume lap.