W = Length of Wire D = Diameter of Pipe L = Length of Pipe (and wire coil) T = Thickness of Wire ∏ = pi W = ∏(D+T/2)(L/T) This should give you what you need under ideal situations The length of the wire is equal to the length of one loop of wire around the tube, ∏(D+T/2), times the number of times it is able to go around the tube, (L/T). If N is 100 turns, l is 6 meters. S = No. n = number of turns. • Coils typically span into two slots in the core, so there are two coils per slot. 5. Since E E → is tangent to the coil, ∮E ⋅ dl = ∮ Edl = 2πrE. The one method that is given in both papers isFront Pitch. Pole pitchis defined as the peripheral distance between the center of two adjacent poles in a DC machine. The resistance of 1 coil is 16,5 ohms. 392699 = (pi*0. 4. It is always less than unity (K c < 1). The pitch can generally be estimated using the following simplified formula. Armature winding is an arrangement of conductors in order to develop the desired emf by relative motion in the magnetic field. e Juice heaters) 0. The axis of the coil coincides with the axis of the solenoid. In conventional three-phase electric machines, coil pitch ratio is usually selected around 5/6 so as to minimize the 5 th and 7 th flux linkage harmonics. If the coil span is equal to the Pole pitch then it is called a full pitch coil. As we discussed earlier that every set of windings in lap windings has no parallel paths equal to poles in a machine, so in duplex lap winding the current paths will be twice. The smaller the value is, the quicker the response is. We also discuss the formula for. A pole pitch is always 180° electrical regardless of the number of poles on the machine. 923 respectively. Fo r. Calculate the OD expansion and compare this to any work in hole requirements. In dc machines, the slot pitch usually lies between 25 to 35 mm. Smax = maximum gradient. These emfs must have same wave shape and be displaced by 1200 to each. This describes the fact that a winding may consist of a number of coils, each linking flux slightly out of phase with the others. Planar coils are mostly used in high frequency applications and designed as tracks on a circuit board. m = multiplicity factor. Coil pitch is the centre to centre distance of the two adjacent pole. In electrical machine, armature winding is distributed in the slots. The Coil Length Calculator is invaluable for engineers and designers when creating coils for various applications, including inductors in electronic circuits, electromagnets, and transformers. The term “Enthalpy” is used to describe the total heat of a substance. Y b = (2S / P) +1. 100. where q is the number of coil per phase, is the angular phase angle between adjacent EMF vectors of one phase (in Elec. 966. of height to diameter ratios, and the topic of heat exchangers of varying ratios of coil pitch to its diameter. Commutator pitch of a progressive lap winding is yc = +1. Key Point: The angle by which coils are short pitched is called angle of short pitch denoted as ‘ α ‘. Figure 4 representsdiscussed in the next section, and the new formula derivation is given in the subsequent sections. Calculate the pitch (and therefore coils per inch) and the spring index. Learn what a pole pitch is, the pole pitch formula & definition, and how to. Counting them is easy enough – every rotation of 360 degrees equals one coil (90 degrees = ¼ coil, 180 degrees = ½ coil). Square the resultant to obtain the numerator. The pitch factor or coil span factor n th harmonics is. Enter the coil spacing or pitch, S = 0. Number of Commutator Segments - Number of Commutator Segments is the count of cylindrical assembly of insulated segments that are mounted on the shaft of the. OD is the outside diameter. are e. 5)/4. Force = applied. Distributed Winding. The mean coil radius of helix (R = D/2) and the cross-section can differ along the helix. 5. You can refere standard reference input image shown in this calculator for your better understanding to this angle value. However, the coil count can be critical and. A SIMPLE explanation of Full Pitch and Short Pitch Winding. So, if this is one-fifth the number of turns in the secondary coil, then in order for the relationship to hold true, the secondary coil must have 500 turns. You can use any dimentional units such as Inches or MM as per your prefererance. 2. The following formula from R. Important points: Back pitch Y B the distance between the top and bottom coil sides of a coil measured around the back of armature is called back pitch. It is equal to the number difference of the conductor connected to a given segment of the commutator. Front Pitch-The number of armature conductors or elements spanned by a coil on the front is called front pitch. kd = (Vector sum of the c. Winding Pitch. f. lt is also known as coil pitch. The value N a is the number of active coils and N t is the total number of coils. The stiffness of your spring depends on the proportion of each spring dimension with all the others. Pitch can change from run-to-run if the coil feed mechanism varies in its setup or is showing wear. 14=78. Coil Span: It is the angular distance between the two sides of the coil. It is always 180° electrical. Correction for this is done by multiplying the voltage equation by Kp, called pitch factor. So say all other aspects of the spring remain constant - coil pitch, inner outer and mean diameter, modulus of rigidity, elasticity, material, etc. Enter the coil diameter (form diameter + wire diameter - see diagram). A coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below. The formula is applied to calculate the ohmic resistance of helical and spiral coils and is verified by a 2-D finite-element-method. This tool is designed to calculate the inductance of a coil of wire given the length of the coil, the number of turns, the loop radius, and the permeability of the core material. Haringx’s [1] formula gives accurate results only when the helical spring has a small helix pitch angle, in other words, when the helix angle is usually less than 10 degrees. m. The flux per pole is 0. We can therefore non-dimensionalize the forces and moment in the following way: C L = L q ∞ S. 912. Spread the love. 3. 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. The total length of the wire used to create the coil. The factor of sqrt 3 3 is needed to convert between the system's phase current and line current. 5 kW) AC vector motor and drive with foot controlled variable. EC = EC1 +EC2 𝑬 𝑪 = 𝑬 𝑪 𝟏 + 𝑬 𝑪 𝟐 Since EC1 𝐸 𝐶 1 and EC2 𝐸 𝐶 2 are in phase, the resultant coil voltage is equal to their arithmetic sum ( Refer the figure of full-pitch coil ). The phase belt is defined as the group of adjacent coil-sides belonging to a phase, as shown in Fig. f. Compression springs consist of open coils (Pitch). In 1952, Francis Crick described a new type of protein structure, which he called the coiled‐coil 2. The benefit is that these parameters can be used to customize this versatile part for a variety of applications, including a helical coil spring and a heat exchanger. Inductance is the property of the coil and tells how good the coil can store magnetic energy. 81 T). Simply enter your numbers to determine flat rolled steel coil lengths and weights. The following formula can be used in production, in order to estimate the weight of coils in production starting from their geometry. The formula for the commutator. 5. diameter is calculated according to the formula D = 2(r + Nd), and the number of the turns is chosen so that D max ≤ D. f. These windings must be properly arranged such that the induced emf in all the phases of the coils must have the same magnitude and frequency. 4×10 4. where: SP is the spring pitch (in/coil) L is the length of the spring (in) D is the diameter of the spring (in) NA is the number of active coils in the spring Spring pitch (p p p): Refers to the space between two adjacent coils and is directly related to the free length value (L 0 L_0 L 0 ) of a spring. Though the formulas . Rotor Inertia The moment of inertia of the rotor, expressed in Jm. 02 wb, N = 375 rpm, for full pitch coil, K p = 1. Its value is always less than unity. In a conical coil spring with a fixed pitch angle, R and n’ (= θ / 2π) are associated with the following formula. 800-348-2529 Get a Quote. For a full- pitch coil α = π. ∴ e = E 1 + E 2 = 2E. (See demonstration 68. CT Ratio = 100:1. The following equation is used to calculate the Spiral Length. Learn MoreCalculator. Add downspouts. Remember to incorporate the high side of the OD tolerance when examining the work in hole requirements. SP = (L-3*D)/NA SP = (L − 3 ∗ D)/N A. μ0 一 vacuum permeability. This formula is, however, a first approximation. Since these terminals are in series, the voltages add up. So, the ending point of a coil in a 4 pole wave winding should be associated just beforehand or just afterward the point midway around the loop from its initial point. C, spring index: C = D/d. 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. 1,2Geometry of spring: d, wire diameter; D, mean coil diameter. S 一 the cross-sectional area of the coil, in square meters. For lap winding, Y = yb – yf. There is a last design parameter but similarly to the pitch, it only matters to expansion/contraction springs: Spring end type: This property refers to how are the external faces of a spring. Deg. 3 τ p + 0. 25” • For 3/8” tube coils, fins are available in increments of 1. It is expressed in terms of electrical space degree. A coil is basically any number of turns. The mean coil radius of helix \(R = D/2\) and the cross-section can differ along the helix. D - coil diameter (cm); p - winding pitch (cm); d - wire diameter (cm). 3. 953. The right-handed helix (cos t, sin t, t) for 0 ≤ t ≤ 4π with arrowheads showing direction of increasing t. The winding pitch of a generator is the number of slots spanned by each coil in the stator winding divided by the number of slots per pole. l——Spiral length. C machine having a total number slots S = 16. So, a discrete coil ends on the 2 nd commutator down from where it ongoing, and Yc=+-2. For Wave winding, Y = yb + yf. When I began writing Part 2c, my goal was simply to code Snow's inductance formula as a simple computer program function. 303K views 6 years ago. Formula: Y R = Y b - Y f = ± 2m. The welding calculator utilizes the above set of weld strength formulae to determine their. L = µ r ( n 2 . For a coil, that is short-pitched by α electrical degrees, the resultant induced emf E R is the phasor sum of two voltages α electrical degrees. You wanted to know the field strength adjacent to the coil. INSTRUCTIONS: Choose units and enter the following: (H) Height (P) Pitch: distance between turns (D) Diameter Length of Helix (L): The calculator returns the length of the helix in meters. 5 D, the coil diameter generally changes with an increase in deflection (load). 0 mm. Add the products of the coil diameter and 18 with wire length and 40 to get the denominator. It is equal to the number difference of the conductor connected to a given segment of the commutator and is represented as Y b = ((2* n slot )/ P )+1 or Back. A solar heater is made like a coil with 20 mm pipe inside a 1 m x 1 m window frame. You do so by subtracting the amount of wires in the closed. Click Calculate. The total length of the wire used to create the coil. (v) For the number of phases, m, each repeatable group consists of m or 2m-phase belts. No. 2 STEP 2 : calculate the required heat flux. 4. In a full pitch coil, the coil span will be 180° electrical (equal to pole pitch). The skew factor reflects the flux reduction if the winding is angularly twisted along the axis. The calculator is designed to accept the total line voltage and current of the combined three cables. 4 August 15, 2007 19 Pitch Number of coils per inch of length m 1 πD P λ=tan− August 15, 2007 20 Spring materials Steel Most common Phosphor bronze Cold wound for small size (<5/16 in) Wound from hot rolled bar August 15, 2007 21 Types of Materials Hard drawn high carbon steel Oil tempered high carbon steel Stainless steel Light-duty springs. Lbs condensate per hour = BTU per hr of coil / *Latent heat of steam *Assumes saturated steam. A pole pitch is always 180 electrical degrees, regardless of the number of poles on the machine. The. A way of understanding what I mean by maximum spring compression - the point before a permanent set occurs in the spring. Where. (iii) All coils have the same pitch. In Unilab Coils it’s not possible to insert more than one fin pitch in the same project, but you can calculate anyway a coil with variable fin pitch, simply considering a “medium” fin pitch resulting from a weighted mean of the real fin pitches. To help better understand pitch and spring index, take a look at Figure 3 (a section view of a compression spring). 1. We can obtain the height of the coil with this expression: H = N * (S + Dw) Length (L). Width can be trimmed on request, but is usually in one of the standard sizes: 1000, 1250, or 1500 mm. Therefore the total emf generated across the armature terminal is. The spring pitch is the distance between adjacent coils of a spring and is typically measured in inches per coil. 4 mm thickness. To calculate the spiral length, multiply the number of rings by pi, then multiply by. m, f, s in all the coils under one pole)/ (Arithmetic sum of induced e. For example, if there are 36 slots and 4 poles, then the coil pitch is 36/4 = 9 slots. The second plot is the field strength at Z=0 along the x-axis. 026 = 192. This spring stiffness calculator will calculate all of the values required to determine whether the spring will be stiff enough to meet its requirements. Coil span factor or pitch factor (K p): The coil span factor or pitch factor is defined as the ratio of the voltage generated in the short-pitch coil to the voltage generated in the full-pitch coil. Thus starting from the pitch and known radius, you can calculate the angle of wrap from θ =tan−1 p 2πr θ = tan − 1 p 2 π r and get the coiling radius as above. Therefore, the correct answer is 500 turns. The unit is kW/s. 29 degree. For example, if there are 36 slots and 4 poles, then the coil pitch is 36/4 = 9 slots. A coil is said to be fully pitched when the coil span is made equal to the pole pitch of the machine. After one turn (an angle increases by 2π), the distance increases by 2πk. In the above figure it can be seen that, coils are distributed in slot number 1,2,3 and 10,11,12. Formulas. Helices are important in biology, as the DNA molecule. ) Thus, when the coils have current flowing in them, they behave as. 2 Breadth Factor Now for breadth factor. The Math / Science. Before getting into the detailed study, learn the. 1. Let, E s = EMF induced in each coil side. I conclude that to eliminate 7th harmonic components of voltages in ac machine , coil pitch must be. The calculation results are verified with several conventional formulas derived. Add to that Kapton tape in between layers (if needed). k 一 a coefficient depends on the ratio of the radius (R) to the length (l) of. Resultant pitch (Y R): Distance between the starts of two successive coils. Know Weight, Thickness and Width of a Coil, want to estimate the LENGTH of Coil. 59 m1. A fractional-pitched coil, on the other hand, is a type of coil used in electrical machines where the coil spans only a fraction of the pole pitch. The shortest path between two points on a cylinder (one not directly above the other) is a fractional turn of a helix, as can be seen by cutting the cylinder along one of its sides, flattening it out, and noting that a straight line connecting the points becomes helical upon re. 00625 in = 0. power of water coil was calculated according to the formula r. Part 2 – Inductance Calculation Refinements. the helical spring actually results in higher shear stresses on the inner surfaces of the spring than indicated by the formula above. 64 × 10 − 27 k g) ( 3. Step 1: Analyse Motor. The procedure consists of these basic operations: 1. P = 154. Winding factor is defined as the ratio of emf generated in short pitch distributed coil to the emf generated in a concentrated coil. A staggered pattern is more commonly used. The pitch factor of the coil at the nth harmonic frequency can be expressed as 1. For the n th harmonic, the chording angle becomes nα° electrical. Total diameter of the coil and winding is 515mm. The formula for total number of spins is (Turns per volts * voltage). The winding factor is often expressed as the product of three factors: the pitch factor (also called chording or coil-span factor), the distribution factor (also called breadth, spread or zone The calculation results of , , , , and for both double-layer windings with a constant coil pitch and single-layer windings with a constant odd coil pitch are all shown in Tables 9 and 10. The spring index typically ranges from 5 to 12. Define Pitch Factor /Distribution Factor and present the formula to calculate. When the winding is full pitched, coil span is equal to the pole pitch. Closed and Ground. Prelude to Synchronous Generator Induced E. If, Z = the number of conductors P = number of poles YB = Back pitch YF = Front pitch YC = Commutator pitch YA = Average pole pitch YP = Pole pitch YR. Coil span is nothing but the distance between the two coil sides. Calculate the inductance associated with the winding using the formula L = (u0 * A * N^2)/l where u0 is the permeability of free space at 12. through formula nes = N 2 mbnwcc n lay, (6) where bnwccis the largest integer less than or equal to nwc. Variable turn pitch (VTP) coils are then proposed to address the eddy currents distribution problem. This advancement is measured in terms of armature conductors and is called front pitch. Figure 4. d = wire diameter. Instructions to use calculator. If the coil is with no space between the pipes the number of turns can therefore be calculated as . This advancement is measured in terms of armature conductors and is called back pitch. INSTALL: The insert with Heli-CoilThe EMF equation of an alternator is given above. Make sure to leave 1-inch lengths of the wire at the top and bottom of each head for the new terminals. R = R i + a θ, θ i ≤ θ ≤ θ o. Steel Processing Portal WI Steel Connect. 8) T = 2 π m q B = 2 π ( 6. If you're making a coil for an atomizer where both the coil legs point in the same direction,. Each coil voltage E C will be out of phase with the next coil voltages by the slot pitch β. D = mean coil diameter. CT Ratio = V p /V s. Q9. This type of coiling design offers a number of advantages, and a wide range of products depend on variable pitch springs to deliver optimal performance. ; Coil Span: It is the angular distance between the two sides of the coil. e. D = inside diameter of the coil (inches) D1 = bare wire diameter (inches) S = space between turns (inches) Using the MCI formula, applied to 47 gauge wire (1. To calculate the resistance of a moving coil meter, you need to first determine the voltage across the coil and the current flowing through it. extent that the coil diameter changes. First, determine the outer diameter. Draw the double layer winding layout for a 24 slot stator and 4 pole alternator 3. 2: Pitch and spring index. For the fundamental. The fractional-pitch coil is also known as chorded coil. This is the direction of the applied magnetic field. Now, What is pitch factor? The ratio of phasor sum of induced EMFs per coil to the arithmetic sum of induced EMFs per coil is known as pitch factor K p or coil span factor K c. For air, enthalpy is expressed in BTU/lb of. 5 mil spacing between turns, wrapping the turns around a 20 mil pin vice, you can make the following air-coil values: 1 turn= 2 nH 2 turns= 5 nH 3 turns = 8 nHAny variation in coil width will change the blank size and affect the location of the blank. In determining the total number of coils in the spring, the. ∴ Pole Pitch = (Number of armature slots. Length = ( diam^2 * pi ^2 + pitch ^2)^0. It may even be found by applying Fleming’s Right-hand Rule. What is flange pcd?From the active length, the total length of the machine can be calculated with Equation (10), where f wc is the winding coil factor L total = L k 1+ f wc (10) The winding coil factor is defined in. 6 × 10 − 6 s. Enter the coil length (distance from first to last winding - see diagram). P——pitch. Helix Angle [clarification needed]. The formula for the commutator pitch in any simplex winding is given as. P = No. Spiral Length Formula. This paper presents a design formula for a printed spiral coil to ensure the maximum quality factor (Q-factor). Free length of spring is defined as the axial length of an unloaded helical compression spring. Enter the scientific value in exponent format, for example if you have value as 0. Additionally, is the slot number while p is the rotor pole pair number. Free length of spring is defined as the axial length of an unloaded helical compression spring. A curvature correction factor has been determined ( attributed to A. al. Both the overall number of turns and the turns per volts are calculated using the Number of Turns of a Coil formula. Two main parts of motor are rotor and stator. The values provided above are inserted into the equation below and computed. . Commutator PitchInductance. Pipe Coil Length Calculator is useful for Calculating reuired length of your pipe coil. Below is the coil length formula: L = π * Dc * N. The pitch of a helix is the width of one complete helix turn, measured along the helix axis. The downward flow isConcentrated Winding. You can read more about Full. The only problem with this type of winding is that its coil cost will be more than other types of winding. The winding pitch cannot exceed the doubled wire diameter; The coil diameter cannot be greater than the doubled diameter of the rod; The winding length should be less than 3/4 length of the rod; When the coil is shifting it should not reach the edge of the core 1/8 of its length; The initial magnetic permeability of the rod should be greater. A SIMPLE explanation of what a pole pitch is in a generator or rotating machine. 881. To find : f, E ph, E LDesign Tips: Coil Count. It is expressed in terms of electrical space degree. This lecture will discuss;1. Coiled‐coils are structurally conserved. What is the CT ratio. ; 1 full pitch = 180° It is denoted by K p and its value is always less than unity. 3. These factors represent the effect of coil distribution on the induced voltage waveform. of polesNo. see the "P" dimension in the image on the right. You can then calculate the pitch in between the coils using the free length and the amount of coils you decided to use. where: SP is the spring pitch in. 2 mil bare wire diameter), and 0. ∴ EC =. You can then use the formula: R = V / I. Main Stator: Coils and Slots • The number of turns and cross section are specific to each frame size, slot combination or design, and voltage. Resultant pitch (Y R): Distance between the starts of two successive coils. This is quite unfavorable due to the geometry. 8. We were told that the primary coil has 100 turns. 1 Å compared to the reflection at 5. (1 – 0. whereas the coil pitch and inner diameter of L2 are exactly the. The external surface: A=L t *pi*d o. A coil having a span equal to 180⁰ electrical is called a full pitch coil as shown in the figure below: A coil having a span less than 180⁰ electrical is called a short pitch coil or fractional pitch coil. TAP: with a Heli-Coil® STI tap (and ream for ANPT) 3. It may be the full pitched or short pitch. Coil pitch or coil span is defined as the angular distance between the two coil sides of one coil. Please use the mathematical deterministic number in field to perform the calculation for example if you entered x greater than 1 in the equation y = 1 − x the calculator will not work and you. R1 = Ri + aq1 (5) R2 = Ri + aq2 (6) q1 and q2 are the angle of revolution of the original and its fictitious spiral coil, respectively. Find the frequency of the induced emf, phase emf and line emf. If the coil pitch is. First, that 10 inches of sidewall metal equals 10,000 lbs of metal and, second, that zero inches of sidewall (when the metal is all used up--the 20 inch core diameter) equals. Therefore, for simple, collective pitch control a simple, modular, spring-mass description is adequate, while in individual pitch control (IPC), possibly coupled with vibration attenuation, a more complex, vector procedure is called for. , 2011). 3 wraps = 14,999. The basic parameters of the coiled-coil are its pitch (periodicity of the supercoil), the associated pitch (or supercoil) angle (angle of the helix with respect to the supercoil. (iii) All coils have the same pitch. 10 mm wide bobbin, 100 turns of 0. The flux linked is: (. 038) ÷ 4 = p Pitch. The coils are short pitched by 3 slots. The maximum gradient can be determined using the following formula: The following applies: Sa = minimum distance. Spring pitch formulas usually take into account the: Geometry of the spring; Stress; Amount of force the spring will experience; Height; Amount of coils; Density of the. 4 are the elastic modulus E, the shear modulus G=E/ 2 1+ with a Poisson ratio , the cross-sectional area A= d2/4 with a wire diameter d,The winding calculator allows you to find the optimum winding layout for your electric motor in a fast and convenient way. 14159*N* (OD+ID)/2 S L = 3. in each coil side. Understand what Full Pitch and Short Pitch Windings are, and what Coil Span is. These coils are short, fat (large-diameter) solenoids. 4 pole = 90º. The Spring Pitch Calculator is a tool that helps engineers and designers to calculate the spring pitch of a helical spring. AWG is converted to diameter by using the formula that defines AWG. L is the inductance in μH. Steam heating coil sizing involves determining the required heat output in BTU/hr based on factors like steam pressure (PSIG), fluid flow rate (GPM), and desired temperature rise (°F). Use pliers to squeeze together the new terminal leads to the copper wire. Hence, the pitch factor or the coil span factor for the n th harmonic is given by, kcn = cos nα 2. To obtain The following formula from R. m. When a coil is having a span of 180° electrical, it is called a full-pitch coil. 20um away, at x=250um, the field strength is 0. The above recommendations assume that you have properly sized downspouts every 40 feet. What is the formula to calculate weight of steel?Using a m athematical formula to calculate condensate volume can help users find the right. The deflection before the coils are. 953. Rotor is usually made as squirrel-cage, and it is inserted in stators hole. Hypothetical at the time, the coiled‐coil was proposed as a solution to the X‐ray fiber diffraction patterns of α‐keratin, which showed a strong reflection at 5. In the stator of a single phase motor, first running winding and later steering winding are put. Formulas. Previously, all of these dimensions were measured from centre to centre of the applicable conductors (as shown in the diagram below). The radius of curvature c c for cable wrapping at such an angle is c = a2 b = r cos2 θ c = a 2 b = r cos 2 θ and the pitch p p is p = 2πr tan θ p = 2 π r tan θ. Y f = (2S / P) -1. It has very good efficiency and low manufacture and maintain costs. I 一 the length of the coil in meters. Calculate a “Free Point” for stuck tubing or the length of free pipe. coil. This works out to be [Math Processing Error] (11. • Pitch = (span -1) × the number of rotor poles / total # of slots. The distance between the two sides of a coil is called the Coil Span or Coil Pitch Factor. Coil span or coil pitch. (v) For the number of phases, m, each repeatable group consists of m or 2m-phase belts. Here Pp denoted the pole pitch in mechanical degrees and P denote the number of poles in the machine. The angle of the spring coil relativeto the mounting. 1 mm wire = 10 layers of wire = 1. Resultant pitch (Y R): Distance between the starts of two successive coils. (iv) Coil-sides are inserted into slots in a single or double layer. The coil span of the alternator is 1 to 8. 17 µH; and for 18 gauge wire it’s 1.