D. the flux per. The coil span is 150 electrical degrees. , Y = 2/3 τ p. 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. ( 2) The harmonic voltages decrease in a short pitch coil, thereby improving the waveform of the induced voltage in the winding. Wc is the coil span , and is the pole pitch measured in the number of coil sides, which is . Calculation: Given that, Slots S = 72. – Comparator. fs. Note. c. Coil span Pole pitch Periodicities Winding factor. Transcribed image text: 1. For alternator having fractional pitch winding of 8/14 the coil span is 102. Calculation:When the coil sides forming a coil are spaced exactly one pole pitch a part they are said to be of full-pitch. 1 is connected to coil side in slot No. It is usually measured in terms of teeth, slots or electrical degrees. the flux per pole has a fundamental component of 0. 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. 12. Assume a coil span of unity. ∴ Coil span factor, Where β is the angle through which the coil is short pitched. In a 10 pole, lap wound de armature, the number of active armature conductor per pole is 50. Calculate the pitch factor for (a) fundamental (b) 3rd harmonic (c) 5th harmonic (d) 7th harmonic. If each coil spans 8 slot pitches, what is the value…Front pitch: The distance between the last side of the first coil and first side of the second coil is called the front pitch. is B = 10 sin theta + 2 sin 3 theta + 2 sin 7 theta kilo - gauss, when theta is measured from the neutral axis. It indicates how the coils are spaced out on the armature core. ( b) 42 stator slots, four-poles, coil. Here, e = E 1 = E 2 = E. 2. If the coil span is equal to the pole pitch, then the armature winding is said to be full – pitched. Obtain a coil span of 180 degrees (electrical) b. 9 and pf = 0. C. of phases = 3; No. Pole pitch = S/P. Assuming single turn coil, calculate the back pitch for progressive and retrogressive winding. Degree of Reentrancy c. m. What are the different types of stator windings in induction motor? Ø. A 4-pole, 50-Hz, star-connected alternator has 15 slots per pole and each slot has 10 conductors. 10 A three-phase, wye-connected alternator has 15 slots/pole. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. Calculate its coil span factor. b) 96 stator slots, 6 pole, coil span 1 to…. the distance between the two sides of coil is called the coil-pitch. 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 . advertisement. M. The pole pitch is 35cm, the core length is 32cm & sta- 4th tor coil span is of pole pitch. At this situation, two opposite sides of the coil lie under two opposite poles. 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). Calculate its coil span factor. 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. . (ii) Pole pitch: The over hang portion of the coils depend upon the coil. The electrical space angle between the active coil length or coil side is equal to one pole pitch. 1, if the coil sides are placed in slots 1 and 7, then it is full-pitched. Coil Span: The number of core slots spanned by the sides of the coil. Pole – pitch. 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. 6. If the coil span is less than the pole pitch, then the winding is said to be short-pitched. m. coil pitch in terms of slots4. In general, electrical degrees equals mechanical degrees times 1/2 the number of poles. 2 sin 30+0. of slots per pole = 15 but coil span is… Q: A synchronous generator has 9 slots per pole. • So coil span is 16/4 = 4. A pole pitch is defined as the peripheral distance between identical points on two adjacent poles. Each of these coil spans is five slots, so this choice of winding pattern is referred to as “Five-Sixths” pitch. The slots per pole per phase are 8 and the coil span is 20 slots. It is possible to suppress the higher harmonics by using double-layer windings using shortened span coils. 866. are e. If we used short pitched winding for armature winding than pitched factor is included in EMF equation in Alternator. The distance between the two sides of a coil is called the coil. The coil span of a full pitch coil is always 180° electrical. 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. Solution : Coil groups per phase = 3 x 4 = 12 Slots per pole per phase, m =24/12 =2 Angle between adjacent slots, â =180/24 =30 For full pitch coils, the coil span, á = 0, ie. Coil Span or Coil Pitch Question 1: For a 6 pole DC armature with 14 Slots having 2. The value of α will usually be given in the question, if not, then assume kc = 1. An alternator has 18 slots per pole and the first coil lies in slots 1 and 16. arrow_forward 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. 05: B) 0. 06 weber distributed sinusoidally over the pole. If the coil span is equal to the Pole pitch then it is called a full pitch coil. to the induced emf in the same coil when it is full pitched is called a coil span factor or pitch factor or chorded factor and it is generally denoted be K p. First. It is using an armature winding which is short pitched by one slot. If coil span is 6 and if top coil side of a coil lies in slot 1 then the. Since one pole presents 180 electrical space degrees so the slots pitch. • Winding pitch is the coil span divided by the pole pitch, e. It is also called a chorded coil. 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. A 4 pole, 12 slot lap wound dc armature has two coil side per slot. 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. Its magnetic poles can be salient (protruding or sticking out from the surface of the rotor), as shown in Fig. 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. 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. it is said to the a fractional-pitch coil. The short equidistant winding of 48 grooves, 4 pole three phase asynchronous motor individual layers of the present invention is totally 12 groups of coils, and every group of coil is comprised of two coils; The pitch of all coils, shape and size are all identical, and coil span is 9; And adopt overlapping method rule and Salient pole. 60o groups, 2-layer winding is used. Q3- A/ 10 MVA, 11 KV, 50 Hz, 3-phase star-connected alternator s driven at 300 RPM. Let n be the number of slots per pole. e. 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. In general, if the coil span falls short of full-pitch by an angle α (electrical)*, then kc = cos α/2. m. A. Determine the equation for the emf induced in one turn, and its RMS value. The primary reason for making the coil span of a d. Determine the pitch factor for winding: 36 stator slots, 4-poles, coil spans 1 to 8. m. A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. 150° is (frac{5}{6}) parts of 180° i. 1 times the pole arc. EE - 422 DC & AC MACHINERY 2nd Semester AY 2020-2021 ENGR. in them are additive. Now labeling the starting end of each coil is easy, assuming an RYB phase sequence taking red as the reference. in the two coil sides. g. Full pitch winding. When measured in electrical degrees one pole itch is equal to 1800. Publisher: McGraw-Hill Education. The stator has two slots/pole/phase and 4 conductors per slot are accommodated in two layers. 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. Back Pitch. Result- ant flux in the air-gap is 5 ´ 10– 2 webers per pole sinusoidally distributed. 455 V D. Give the values of front pitch, back-pitch and commutator pitch. It is one pole pitch. armature winding equal to a pole pitch is to (a) obtain a coil span of 180º (electrical) (b) ensure the addition of e. Transcribed Image Text: (d) obtain a full-pitch winding. Here we can define one more term related to a coil called coil span. c. Thus, the total. Assume the coil span as 150° electrical. Show transcribed image text There are 3 steps to solve this one. 956 1. The distance between the two coil-sides of a coil is called coil-span or coil-pitch. Thus the total emf at the coil terminal A & B is the phasor sum of (E 1 +E 10), (E. A 6-pole, 3-phase, 60 cycle alternator has 12 slots per pole and four conductors per slot. 26. Chorded-coil. Watch to understandPole Pitch, Full Pitch Coil, Short Pitch Coil, Coil span, Mechanical & Electrical DegreeThere are many people who want to. 2. 1. because of that the pole pitch is 9/4 of the slot pitch, thus the three-phase symmetric distributed windings consist of 18 double-layer coils that can be used, in which each coil span. slots. , a pitch, or an pitch, etc. 2. Pole pitch = 180 electrical degrees = S/P = 2C/P. 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. If the machine gives 3300 V between lines on open circuit with sinusoidal flux distribution. ) A 6-pole, 3-phase, 60-Hz alternator has 12 slots per pole. Winding table. (2) 𝑘 𝑐 𝑛 = c o s 𝑛 α 2. of consecu- tive turns (c) distribute the winding. 15. The Separation between the top and bottom sides of a coil is known as back pitch and is represented by (Y b). 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). To get a coil around every tooth, we need two winding layers (double layer winding). Pitch factor. e. Each of these coil spans is five slots, so this choice of winding. Draw the developed diagram andshow the positions of brushes. Calculate the distribution factor for a single layer 36 slots 2-pole three-phase stator winding. 4. Let us assume that, a coil is short pitched by an angle α (electrical degree). (5/6) of a pole pitch. The distribution of upper-side voltage phasors is the same as that of coil voltage phasors,. 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. 2 Winding design with star of slots The star of slots is a collection of phasors which illustrates allIf 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. Boylestad. The width of the coils is 5/6 of the pole pitch. Expert Solution. Determine the phase andline values of emf if the machine runs at 600 rpm and the flux per poleis 0. Q: For alternator having fractional pitch winding of 8/14 the coil span is 102. Pole arc/ pole pitch = core length/ pole pitch = 0. c. Prob. Get Coil Span or Coil Pitch Multiple Choice Questions (MCQ Quiz) with answers and detailed solutions. Zoom In Zoom Out Reset image size. It is sometimes convenient to speak of an armature coil span as having a fractional pitch expressed as a fraction e. If the coil span is from slot 1 to slot 21, and the flux per pole has a fundamental component of 0. 24 B where coil pitch is 3/4th of the pole pitch), then the D. 85 lagging. Pole pitch is always equal to 180. The coil span is 10 slots. 0. Where n is the nth harmonic. • In double layer windings used in. 7. 6. Hence, the coil span in three phase AC machines must be (frac{5}{6}th) of pole pitch. Question. of consecu- tive turns (c) distribute the winding uniformly under different poles (d) obtain a. Hence E. The reduction fraction is the pitch factor. A pole pitch in an electrical machine is equal to 180° electrical. #Alternator #Protectionofalternator#elect. ∴ e = E 1 + E 2 = 2E. 24, and assume first a short-pitched coil spanning half a pole pitch, then a long-pitched coil spanning one and a half. . 0. It is always equal to 180° electrical. The flux per pole is 80 m Wb and the coil span is 160° electrical. Thus, the total. M. 2. 0 B. 0 B. 924 359. 10. fs. u. (a) 1 and 10 (b) 1 and 9 (c) 2 and 11 (d) 3 and 12 (C) frog (d) mu 12. Pole Pitch: It is the angular distance between the two adjacent poles. m. Determine the useful flux per pole. [8+8] 2. ISBN: 9780133923605. Identify the approximate diameter and length of stator core,. e. The pitch factor. Muthu RE: How. 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. 3 percent. 4. When a coil. The armature windings conduct AC even on DC machines, due to the commutator action (which. , pole-pitch ) is known as 'Full Pitch'. , Y R = Y B − Y F . Pole pitch = 180 electrical degrees = S/P = 2C/P. It equals pole pitch = Z P . the core length 32 cm, and. I need answer within 20 minutes please please with my best wishes. Normally the nearest whole number is selected which is 6 in present case. A pole pitch is always 180° electrical regardless of the number of poles on the machine. They are two basic physical types for the windings. The coil-span chosen is of course less than the full-pitch. B. Pole pitch is the peripheral distance between two adjacent poles. armature, 180 electrical-degree coil span will be obtained when coils occupy. Resultant pitch Y R is even, being the arithmetical difference of two odd numbers, i. ISBN: 9780073373843. This distance is measured in terms of armature slots or armature conductors that come between two. advertisement. 0. 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. – Comparator. Coil–span or coil-pitch: The distance between the two coil-sides of a coil is called coil-span or coil-pitch. DARWIN M. arrow_forward A four-pole three-phase 50 hertz, star connected AC generator has 12 stator slots. What is the coil span for a 4 pole 48 slot machine? Explanation: Slots per pole = 48/4=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° ⇒ Kp=cosε/2=0. The flux per pole is 0. The coil span is 150°. 1-9 coil span A SIMPLE explanation of what a pole pitch is in a generator or rotating machine. Distribute the winding uniformly under different poles d. The total flux per pole is 10⁶ lines. The winding is 5/6 pitch. The pitch factor of an alternator is a measure of the winding distribution along the armature. 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. Coil span or Coil Pitch. For a simplex lap winding, the commutator pitch YC = 1 and coil span YS ~ pole pitch. phase shift with emf induced in the other side of the coil. 31. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. Calculate the pitch factor for an alternator winding with 36 slots, 4 poles, and coil span of 1 to 8. c. 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. Solution for For alternator having fractional pitch winding of 10/14 the coil span is 4. 85. (2006), “Distribution, coil-span and winding factors for PM. When the. e. If the coil span is less then one pole pitch than it is called short pitch coil. In such coils, the two coil sides are not under the poles. Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding. In a fractional pitch winding, the coil span is made less than 180 degrees electrical space. 5. The rotor is a large electromagnet. Coil span Coil span (also known as coil pitch) is the angular distance between two sides of a coil, measured in terms of armature slots. 0. Ensure the addition of e. Because a chording more than 1/3 pole pitch would noticeably reduce the phase emf. 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. When the coil is having a span of less than 180. Short-pitched coils are deliberately used because of the following advantages: 1. Compared to the overlapping winding above we need only 3 slots for the two poles. 7. 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. . 1 and No. winding is fractional-pitched. Each phase in this case consists of four coils (two per slot). The two sides of a coil are places in two slots on stator surface. The flux per pole is 0. is known as coil span. It falls short by 1/6 pole-pitch or by 180°/6 = 30°. 4. The coil span is 160°. Register to editPitch factor problem. If the high speed coil span was 1/2 of pole pitch, then there would be roughly equal airgap circumference for induced poles as exists for the driven poles in slow speed, and no need for homopolar flux in the shaft. A coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below. If the coil-span (or coil-pitch) is equal to the pole-pitch, then the coil is termed a full-pitch coil. The pole pitch is always 180 degrees electrical regardless of the number of poles in a machine. Its flux per pole is 0. Both Y B and Y F should be nearly equal to a pole pitch. Electrical Engineering. Assume that the coil span is 150° electrical. 0 i D. 75 times the slot pitch), the lowest with 2-solt span coil. Participate Now!Since 1 pole pitch is the angular distance between the two consecutive poles which is equal to 180 electrical degree, therefore the coil span for full pitch coil is also equal to 180 electrical degree. Pole pitch is always equal to 180o. 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. P. It is usually measured in terms of teeth, slots or electrical degrees. 966The pole pitch, mQ ′ ∕ p, is also fractional, so that the coil-span cannot be of full-pitch. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. When the coil span is equal to pole pitch (180 deg electrical), the winding is called full pitched winding. m. If the coil span is equal to the pole pitch, then the armature winding is said to be full pitched. (a)Find the total number of coil groups in the machine. The coil span or coil pitch for short or fractional pitch coil is less than 180 electrical degree. Expert Solution. 25 slots. Coils 1, 2 and 3 shown in Fig. The fundamental pitch. 15 situated at the center of an N pole rotating in clockwise direction. Coil pitch or coil span is defined as the angular distance between the two coil sides of one coil. 26. 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. . Coil Span (ii) Resultant Pitch. 966 and 0. No matter how many poles, each pole always spans exactly 180 electrical degrees, and it is called pole pitch. 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. 8. The pitch of the coil has 4 slots less than the pole pitch. Figure 8 compares computed waveforms of phase back emf. 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 ____________. 50Hz alternator with 2 slots per pole per phase and 4 conductors per slot in two layers. Calculate the armature winding distribution factor. The coil span is 150°. The phase spread is 60° and the flux per pole is 25-8 x 10 weber. For n th harmonic. 150 degree (electrical). In this case, there is a phase difference between the e.