Hence these types of slots are rarely used in 3induction motors. Calculate, i. XM = 42.2 Each coil has half as many turns and wires in parallel but twice the total number of coil sets. 4th (harmonic) component of EMF induced in stator winding. As its name suggests, a stator does not move, but it provides the force that drives the rotor. Download scientific diagram | Stator slot dimensions. With Bts = 1.5-1.65 T, (Bts = 1.55 T), from (5.22) the tooth width bls can be determined: From technological limitations, the tooth width should not be under 3.5 10~3m. A 50kW,3 -phase, 60 Hz,3 pole pair induction machine with 72 stator slots is assumed in this project. For example, if a slot liner is used to insulate the stack, it will seldom conform perfectly to the slot and fill in the corners, creating dead space. Double layer winding: Stator windings of alternators are generally double layer lap windings either integral slot or fractional slot windings. Some of the greatest challenges for a custom stator manufacturer are related to maximizing the amount of copper wire inserted into each slot (commonly referred to as slot fill) to maximize torque output. Coil bundle size refers to the number of turns per coil and the number of wires in parallel. For applications where power density is critical higher slot fills are possible, but with increasing slot fill comes increased manufacturing complexity which drives cost up and increases the risk of quality issues. 20 Hp motor 3Ph. In addition, depending on the manufacturing process and how they are being held, laminations can shift as they are stacked. This feature in adjunct to other advantages of the SynRM . A CAD model of the lamination or slot geometry can sometimes provide this measurement. This size range provides a good copper to insulation ratio, is durable and easily formed, and is small enough to be readily worked. m D,-----3 D 5. d) Calculate the efficiency of the generator. Full pitched or short chorded windings may be employed. Once the width of the slot is estimated the insulation required width wise and the space available for conductor width wise can be estimated. iii. Bending of top coils is involved in multi turn coils where as such bends are not required in single turn coils. With our comprehensive range of stator, armature and rotor . The larger the opening, the easier it is to insert the wire, but a larger slot opening can have a negative impact on flux path. You shouldn't let yourself be blind to signals of change nor should your staff believe that you are not in the loop on these issues. ramps), lighting design, landscaping, drainage, and overall traffic flow including that of pedestrians. The dimensions of the machine's stator slots are shown in Figure 1 with all . Median response time is 34 minutes for paid subscribers and may be longer for promotional offers. connected scuirrel-cage induction motor has, A:As we have given: density of 0.8 T. The, A:Given: An 8-pole lap-wound dc generator is designed to have The expression for the synchronous, A:Since you posted the multiple questions. The depth of the strands is limited based on the consideration of eddy current losses and hence it should not exceed 3mm. 6 D c c-----1 2, 4, 6 4, 6, 8 The outer diameter of the stator core (as a preliminary) D D a (2.23) Large segment of the chord 1 Z Z D H c a c (2.24) The number of turns per phase 1 1 1 1 a p u q w s (2.25) of conductor per slot, (iv)Mica or bituminous layers to separate the insulated conductors, (v)Coil separator between the layers, The length of the mean turn depends on the following factors. A 20 Kw , 440 V, short-shunt compound dc generator has a full-load efficiency of 87%. (iv)Slot dimension: Length per turn depends on the average size of the slot. Normally the width of the strands is assumed between 4 mm to 7 mm. Hence turns per phase Tph= Eph / 4.44 fKw. Rounded bottom slot shapes resolve both problems. Coils with random winding can cross over each other and will not be consistently layered in the slots. This depth of the stator core can be calculated by assuming suitable value for the flux density B. leads to custom motor designs where the emphasis is on performance over cost and manufacturability; as production volumes increase, cost and manufacturability generally become more important. Now, we proceed in calculating the teeth saturation factor 1 + Ksl by assuming that stator and rotor tooth produce same effects in this respect: with Bts = 1.55 T, from the magnetization curve table (Table 5.4), Hts = 1760 A/m. Stator winding is made up of former wound coils of high conductivity copper of diamond shape. The slot loading should not exceed 500 Ampere conductors. To calculate the following design parameters It is given that: (iii)Voltage of the machine: The insulated conductor coming out of the stator slot should have straight length beyond the stator core which depends upon the voltage rating of the machine. When the dimensions of the stator slot change, the closed-loop regulation of the control system ensures that the operating conditions of the motor are kept constant. Usual value of current density for stator windings is 3 to 5 amps. The double-back coil uses half as many turns and same number of wires in parallel but twice as many coils, which increases the overall length of the wound coil set. Generally full pitched double layer windings are employed for stator windings. (iii)Bending of top coils is involved in multi turn coils where as such bends are not required in single turn coils. Allow 1.5V per brush for contact drop Calculate the efficiency. Slot dimension: Length per turn depends on the average size of the slot. In random coil windings, more turns and more wire in parallel leads to a large coil bundle with many wires crossing each other without a set pattern. Stator slots: in general two types of stator slots are employed in induction motors viz, open clots and semiclosed slots. rpm when, A:for a delta connected induction motor Do only part (a), (b) & (c), A Short shunt compound generator delivers a load current of (16)A at 400V. Hence higher value is assumed for low voltage machines and small machines. X,, Q:three-phase, 3 KV, P=24, 50Hz, Y-connected slip ring IM has a rotor resistance of 0.015 ohm and a, Q:A DC shunt generator has avoltage on open circuit of 150V. Slot fill percentages of 80 or more may be possible if the aspect ratio is less than 1. From generated EMF we will, Q:DC shunt 1200 rpm to the generator shaft. Practice bears this out. To further improve slot fill, some additional manufacturing techniques can be implemented in place ofor in addition togood design. However in case of turbo alternators variation of flux density along the depth of the slot is appreciable and hence the width of the tooth may be estimated corresponding to the flux density at the top section of the tooth or the width of the tooth at the air gap. A suitable value of current density has to be assumed considering the advantages and disadvantages. To identify and offset some of these technical challenges, advanced manufacturers are working with dummy stacks that are 3D printed out of plastic or made from steel using electrical discharge machining (EDM). Design engineers must account for every component that will occupy the limited space of a stator slot. Following are the advantages and disadvantages of selecting higher number of slots. The number of turns in the stator winding is 1000. (i)Multi turn coil winding allows greater flexibility in the choice of number of slots than single turn bar coils. Academic library - free online college e textbooks - info{at}ebrary.net - 2014 - 2022. Sectional area of the stator conductor as= Is/s wheres is the current density in stator windings. 100 2, armature, A:In this question we need to find a power genrated by a armature, Q:Q3: There are no rules for selecting the number of slots. Estimate the stator core dimensions, number of stator slots and number of stator conductors per slot for a 100 kW, 3300 V, 50 Hz, 12 pole, star connected slip ring induction motor. Based on the sectional area shape and size of the conductor can be decided. The variables bos, hos, and hw are assigned values from past experience: bos = 2 to 3 mm < 6g, hos = 0.5-1.0 mm, and wedge height hw = 1-4 mm. Q=335hpV=2000VP=6f=60Hzr1=0.2r2'=0.203re=450x1=0.707x2=0.707x=77, Q:11. However the slot width will be varying from top of the slot to bottom of the slot with minimum width at the bottom as shown in Fig. But looking into the advantages and disadvantages of higher number of slots, suitable number of slots per pole per phase is selected. DMCA Policy and Compliant. In order to analyse the impact of stator slot dimensions on the loss distribution and temperature field of the motor, the inverter and motor are modelled as a whole part in this study. to supply a load of, A:we will use KVL and KCL to find the armature current and generated EMF . A basic single-phase motor usually has four slots that contain two pairs of coil windings, each offset by 90 degrees; a basic three-phase motor has six slots with three pairs of coil windings, each pair offset by 120 degrees. GLASS FIBER REINFORCED MICA TAPE For large size motors, stator windings . A 25 HP, 6 pole, 50 Hz, 3-phase slip ring induction motor runs at 960revolutions per minute on full load with a rotor current per phase of 35 A.Allowing 250 W for the copper loss in the short-circuiting gear, and 1000Wfor mechanical losses, find the resistance per phase of the three-phaserotor winding. If V and f were both halved, what would be the increase in starting torque from the normal direct-on-line start at rated voltage and frequency? Stator slot pitch at the air gap surface =, EMF equation of an induction motor is given by, Hence turns per phase can be obtained from emf equation, Area of cross section of stator conductors can be estimated from the. It is important that high quality machines and tools are used in the manufacturing process to achieve this condition. The number of slots depends on how many phases of power are provided to the coil windings. The wedge is held in place by the foot of the tooth to keep the wire in the slot. (a) The approximate outer diameter and length of the rotor core Q:Three-phase 460-hp, 415 V, 4-pole, 50 Hz induction motor is operating at overvoltage of 480 V and, A:Rotor speed = The torque ripple is greatly affected by the stator slot and teeth dimensions, especially by the slot opening b s0: for the 40-slot stator, it varies from 9.45 to 36.82% as illustrated in Fig. CIRIA Report C750 (Preene, (Groundwater Lowering in Construction: A Practical Guide to Dewatering). A square pole design may be assumed and the stator leakage impedance voltage drop may be ignored. This way, you will learn about changes that may involve your department. Outer Diameter - 520.5 mm; Inner Diameter - 330 mm; Shaft Bore - 105 mm; . Beyond slot design, coil winding and insertion techniques can affect manufacturability and slot fill. Maximum flux density in the stator teeth may be taken to be less than 1.5 times the above value. Here the armature, Q:A 12 KW shunt generator having an armature circuit resistance of 0.8 and a field resistance of 120. With bos = 2.2 103m, hos = 1 10~3m, and h = 1.5 10"3m, the slot lower width bs, is. (v)Machine made multi turn coils are cheaper than hand made single turn coils. 12. with external rotor architecture (Ex-SynRM) has a wider stator slot area, which enhances the torque producing capability of the motor [2, 3]. Estimate the stator core dimensions, number of stator slots and number of stator conductors per slot for a 100 kW, 3300 V, 50 Hz, 12 pole, star connected slip ring induction motor. Multi turn coils are usually arranged in double layer windings in slots as shown in Fig XXX. This is accomplished by scoring the unbalance in the current and voltage waveforms as well as in Park's Vector, both for current and voltage. Solve this question to chose the correct answer for the following: One is often called a double-back coil; the other is known as 2-coilsmake-1. This is considered here a reasonable value. As mentioned above, a slot opening must allow wire to pass through during insertion and accommodate some manufacturing aids that protect the wire from the edges of the steel teeth, especially when slot liners are the primary means of insulation. During insertion, the first prototype would not allow all the wire to fit. 1. Design and Performance Decisions Beginning with the intended application, engineers adjust the specifications of all these factors to design a motor that meets performance requirements and can be manufactured economically. Each slot of the stator conductor consists of two stranded conductors as shown in. Number of stator slots must be properly selected at the. all parameters primary, A:3-phase Induction Motor- Following are the advantages and disadvantages of selecting higher number of slots. A:As per the guidelines of Bartley we supposed to answer first three subpart only. Determine: Consequently, the stator tooth mmf Frals is. The motor has a full-load efficiency of 85% and a full-load power factor of 0.8. (b) the air gap length of the motor These linear slot diffusers feature fully adjustable, aerodynamic pattern controllers fabricated from extruded aluminum, and are available in a large selection of frame styles. If the, A:As per our guidelines we have to solve 1st question 20 Hp inverter 208-230/460 VAC 3 Ph. 2. Now from (5.10) with Bg = 0.7 T, The number of turns per phase W, (from Chapter 4, Vol. Lip of the slot is taken 1.0 to 2.0 mm. a- Draw the equivalent circuit of three phase induction motor referring The losses at these operating conditions are as follows: The stator conductor loss is 12.6kW, the rotor conductor loss is 10.4kW, the core loss is 11.00kW; and rotational losses is 4.129 kW. (d) the number of conductors per slot, if 3 slots per pole per phase are chosen. Total slot fill includes the cross-sectional area of all materials going into the slot: wire, liners, wedges, etc. Aspect ratio is a product of design, driven by application requirements. (iii)Tapered slots: In this type of slots also, opening will be much smaller than the slot width. In case of large generators where the stator current exceeds 1500 amps single turn coils are employed. Hence slot width should be so selected such that the flux density in tooth is between 1.6 to 1.8 Tesla. A custom builder may achieve slot fills up to 65 percent on a stack with an aspect ratio of 10, while a slot fill percentage of 70 requires an aspect ratio closer to 3. Multi turn coils are former wound. Q, 0.2 Q, Q:2- A 4-pole compound generator has armature, series-field and Out ofwhich almost more than 25 % is the insulation. c) Load peak voltage (VT =?) Hence in order to eliminate the eddy current loss in the conductors, stator conductors are to be stranded. Despite advances in automation, stator coil windings made by machine are still limited to lower slot fill factors. impedance Z, =, Q:Q: A 8-pole lap-wound dc generator Download scientific diagram | Stator slot dimensions from optimal design [84]. The three phase windings of the synchronous machines are always connected in star with neutral earthed. i.What is the speed of the rotating stator field?What is the frequencey (in Hz) of the rotor current. Though there are no rules for selecting the number of stator slots considering the advantages and disadvantages of selecting higher number slots comprise has to be set for selecting the number of slots. Conductor cross section:Area of cross section of stator conductors can be estimated from the statorcurrent per phase and suitably assumed value of current density for the stator windings. Operating performance of the induction motors depends upon the shape of the slots and hence it is important to select suitable slot for the stator slots. We also offer customization . Two relatively coil designs allow engineers to break down coil size without changing the number of parallel wires or turns in the coil. Thickness of coil separator is 0.5 mm to 0.7 mm for low voltage machines and 0.8 mm to 1.2 mm for high voltage machines. Slot insulation details along the conductors are shown in Fig. induction motor from the, Q:The results of the no-load and blocked rotor tests on a three-phase, 2200 V, six- 6 3 D 5. Crawler 5-Slot Stator 11 Turn 540 Size Brush Motor by Surpass Hobby. The number of stator segments is dependent on the inner diameter of stator. Normally the width of the strands is assumed between 4 mm to 7 mm. A three phase, 50 Hz, 4800V, 6 pole Y-connected synchronous generator connected to an In this paper, an approach to detect stator winding short-circuit faults in squirrel-cage induction motors based on Random Forest and Park's Vector is proposed. (c) the turns per phase Problems. Normally different types of slots are employed for carrying stator. Mica paper tape insulations are provided for the portion of coils in the slot and varnished mica tape or cotton tape insulation is provide on the over hang portion. For the 60-slot stator, it varies from 4.35 to 13.62% with lower values at smaller slot opening as shown in Fig. Suitable thickness of insulation called coil separator separates the two layers of coils. From these two equations, the unknowns bs2 and hs can be determined as follows: Using (5.24), the slot useful height hs can be determined as. (i)Gross length of the stator core: Each turn consists of two times the gross length of stator core. This can lead to slots that are not 100 percent straight, potentially affecting overall slot fill of the whole stack. Assume also that the winding is full-pitched and uniformly wound. Also, if the slot opening is too small for the wire to pass through, the wire must be wound into the slots turn by turn. Hence width of the tooth may be estimated . The ampere-turns determine the MMF required to induce the desired flux-density in the stator core and the stator core area, in turn, determines the core and air-gap flux. R1 = 0.12 Going back to (5.12), we have to recalculate the actual airgap flux density B,,: As high efficiency is required, and in general, at this power level and speed, winding losses are predominant, from the recommended current densities: In general, if dCo > 1.3 mm, in low-power IMs, we may use a few conductors in parallel ap. To define the maximum full level for the slot, the engineer must decide where to close off the slot opening. FIGURE 5.4 Recommended stator slot shapes. End connection of multi turn coils are easier than soldering of single turn coils. The largest common divisor of Ns and p, (36, 2) is t = p, = 2, and thus, the number of distinct stator slot emfs Ns/t = 36/2 = 18. Becausestatorsare cylindrical, the slots are shaped like wedges. 22 . A 20 Kw , 440 V, 1. The stator slot pitch xs (from 5.3) is ts = 9.734 mm. Privacy Policy, X2 = 0.15 What must be the useful flux if, Q:3. Three-phase 460-hp, 415 V, 4-pole, 50 Hz induction motor is operating at overvoltage of 480 V and reduced load of 80% of the rated value and draws a line current of 624.06A. Machine made multi turn coils are cheaper than hand made single turn coils. No single feature is always best; every design is the result of tradeoffs. 1.5A 10pole, 380 V, 50 Hz, Dconnected threephase induction motor is rotating a quarry belt conveyor. The detailed dimension of the slot can be estimated as follows. However, if high efficiency is the target, such a solution is to be used cautiously. Stator Stack - 315 Frame 4 Pole . This reduces the available slot area and can increase the difficulty of insertion. The goal in designing slot shape is to maximize capacity for copper and other components while minimizing impact to magnetic flux or manufacturability. Also, the calculations will need to account for the gaps left between windings of round wire. is the current density in stator windings, Hence higher value is assumed for low voltage machines and small machines. $28.07. The flux density at this section should not exceed 1.8 Tesla. Insulated electrical coils of copper wire are inserted into the slots and arranged so that current passing through them creates an electro-magnetic field. Further the slots should not be too deep also other wise the leakage reactance increases. ShuntfieldresistanceRSh=75Armature-brushresistanceRA=0.03Seriesfield, Q:-) Total Armature Winding resistance of 200kW, 380V self-excitation shunt generator is 0.07 and, A:DC Generator: Given these constraints, the aim winding factor kwmay be assumed as 0.955 for full pitch distributed winding unless otherwise specified. If it is above 5 mm2then rectangular conductors will be employed. 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. The dimensions of individual strands are selected based on electrical considerations and the manufacturing requirements. is designed to have an average air One is to simply increase the stator outer diameter until Bcs ~ 1.4-1.7 T. The second solution is going back to the design start (Equation 5.1) and introducing a larger stack aspect ratio X which eventually would result in a smaller Djs, and, finally, a larger back iron height bC!i and thus a lower Bcs. Within the frame is a magnetic core for creating and containing a magnetic path. which almost more than 25 % is the insulation. Each turn of the multi turn winding is to be properly insulated thus increasing the amount of insulation and reducing the space available for the copper in the slot. In such type of slots assembly and repair of winding are easy. Greater need for motor optimization often. DMCA Policy and Compliant. To calculate total slot fill, an engineer will start by determining the total area of the bare slot. Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail, Design of Electrical Machines : Synchronous Machines : Design of stator winding - Design of Synchronous Machines |, Design of stator winding - Design of Synchronous Machines. induction, A:Given Data: (iv)Replacing of multi turn coils difficult compared to single turn coils. Induction motor windings are presented in Chapter 4, Vol. Assume, Average gap density=0.4 Wb/m2, ampere conductors per metre = 25,000 A/m, Efficiency = 90%, Power factor = 0.9 and winding factor = 0.96. designed to have an average air gap flux Selection of number of stator slots:Number of stator slots must be properly selected at thedesign stage as such this number affects the weight, cost and operating characteristics of the motor. Hence in this type of slots assembly of windings is more difficult and takes more time compared to open slots and hence it is costlier. Q:A 3-phase, 440-V, delta-connected, 4-pole 50-Hz induction motor runs at a speed of 1447 Applied torque is given, As stack length increases while OD remains constant or declines, the maximum possible slot fill factor decreases while the difficulty of manufacturing increases. *Response times may vary by subject and question complexity. Evidently Bcs is too large. These simulations allow manufacturing teams to try a slot fill, define tooling, and provide better feedback to designers earlier on in the design cycle of new product development. On average, copper wire accounts for 65 percent of total slot fill. Following are the advantages and disadvantages of double layer windings. Voltage of the machine: The insulated conductor coming out of the stator slot should have straight length beyond the stator core which depends upon the voltage rating of the machine. spread over an area of 15 mm?. As a guideline the ratio of slot depth to slot width may assumed as 3 to 5. The value of 1.15 mm is standardized, so each coil is made of 15 turns and each turn contains 2 elementary conductors in parallel (diameter dcQ = 1.15 mm). Free shipping. The detailed dimension of the slot can be estimated as follows. Using the design data obtained so far outer diameter of the stator core can be calculated as. Equivalent Coreloss Resistance..900 . These emfs must have same wave shape and be displaced by 120, Better waveform: by using short pitched coil, Saving in copper: Length of the overhang is reduced by using short pitched coils, Lower cost of coils: saving in copper leads to reduction in cost, Fractional slot windings: Only in double layer winding, leads to improvement in waveform, Difficulty in repair: difficult to repair lower layer coils, Difficulty in inserting the last coil: Difficulty in inserting the last coil of the windings, Higher Insulation: More insulation is required for double layer winding, Wider slot opening: increased air gap reluctance and noise, Slot loading must be less than 1500 ac/slot, Slot pitch must be with in the following limitations, Area of cross section of stator conductors can be estimated from the stator. This slot space factor so obtained will be between 0.25 and 0.4. Comparisons of the two types of coils are as follows. The radius can be optimized to allow the wire to fill in more space around the slot edges. The flux density at the 1/3rdheight from the narrow end of the tooth can be calculated as follows. Repeat (d) for the machine to develop a. The size and number of slots determine how much wire can be contained in each coil, and the wire diameter determines the amount of current that can pass through the coil. Magnetising Reactance..16.8 The various strand of the bar are transposed in such a way as to minimize the circulating current loss. Consequently, the whole design procedure has to be brought back to Equation (5.10). The slot insulation process for electric motors is to provide a barrier between the copper wndings and the steel lamination for all stator, armature and rotor products. Size of the slot Normally different types of slots are employed for carrying stator windings of induction motors. However for fractional slot windings number of slots/pole/phase may be selected as 3.5. Hence in this type of slots assembly of windings is more difficult and takes more time compared to open slots and hence it is costlier. Advantages of higher value of current density: (i)reduction in cross section, Disadvantages of higher value of current density, (i)increase in resistance, (iii)increase in temperature rise. The various strand of the bar are transposed in such a way as to minimize the circulating current loss. A 10 kW shunt generator having an armature circuit resistance of 0.75 ohm and a field resistance of 125 ohm, generates a terminal voltage of 250V at full load. R2 = 0.0.3 The last thing to be measured is magnet wire area. short-shunt compound dc generator In the 2-coils-make-1 method, each set has the same number of coils. Calculate the induced EMF and the armature current. However the slot width will be varying from top of the slot to bottom of the slot with minimum width at the bottom as shown in Fig. and a moment of 238.73 Nm is applied. of conductor per slot, Mica or bituminous layers to separate the insulated conductors. That means measuring the cross-section area of each item, multiplying that area by the number of times that item is placed in the slot (such as the number of copper coil windings), adding the total area of all items, and dividing that result by the available area in the slot. If now the machine is run up to speed from a variable-voltage, variable-frequency supply, calculate the required terminal voltage and frequency to give the 'safe' torque calculated above: (i) at starting, (ii) at 500 rev/min. One way to increase conductor area is to use a larger gauge of conductor to get more copper with less insulation. This method can allow for higher slot fill since the tooling is all external to the stator and you do not need to have the wire pass through a slot. The term natural A temporary works groundwater lowering well (Figure 16.2) typically consists of a well screen and casing installed centrally inside a borehole formed by a drilling rig. Based on such knowledge, we choose the number of stator slots N s: A two-layer winding with chorded coils: y/x = 7/9 is chosen as 7/9 = 0.777 which is close to 0.8, which would reduce the first (fifth-order) stator mmf space harmonic. Each slot of the stator conductor consists of two stranded conductors as shown inFig XXX. per min. This slot space factor so obtained will be between 0.25 and 0.4. (i)Better waveform: by using short pitched coil, (ii)Saving in copper: Length of the overhang is reduced by using short pitched coils, (iii)Lower cost of coils: saving in copper leads to reduction in cost, (iv)Fractional slot windings: Only in double layer winding, leads to improvement in waveform, (i)Difficulty in repair: difficult to repair lower layer coils, (ii)Difficulty in inserting the last coil: Difficulty in inserting the last coil of the windings, (iii)Higher Insulation: More insulation is required for double layer winding, (iv)Wider slot opening: increased air gap reluctance and noise. Now, we have to choose a standardized bare wire diameter from Table 5.3. This also happens in stacks with powder coating: Sharp corners typically lead to buildup of excess powder coating and create similar dead spaces in the slot that cannot be used by the wire. The inner stator diameter is 0.245 m and the machine has short pitched double layer distributed copper windings with pole pitch of 0.85 and 12 conductors per slot. In principle, the higher the aspect ratio, the more difficult the design becomes to build. from publication: Permanent Magnet Brushless DC Motor and Mechanical Structure Design for the Electric Impact Wrench System | This paper . 10. When machine is on load, the terminal, A:DC machines (Generator/ Motor) are the important parts of electrical drives. Multi turn coil winding allows greater flexibility in the choice of number of slots than single turn bar coils. . Your staff has to think that you know what (The managers question and answer book), There have been numerous theoretical and practical studies of design methods for granular filters in relation to water supply wells and for dams. 10. Stator Slot Dimensions. Usual value of current density for stator windings is 3 to 5 amps/mm. Free shipping. 1, (4.9)) is. To achieve higher slot fills, manufacturers look to develop unique solutions such as new compression methods to fit the wire into the slots. Assuming that all the airgap flux passes through the stator teeth: KFe = 0.96 for 0.5 mm thick lamination considers the influence of lamination insulation thickness. full-load efficiency = 87%, Q:The following information is given for a 300-kW, 600-V, short-shunt Though there are no rules for selecting the number of stator slots considering the advantages and disadvantages of selecting higher number slots comprise has to be set for selecting the number of slots. Table 3 shows the dimension of the stator slot. Induction motor windings are presented in Chapter 4, Vol. 1.5.3The Motor. The flux density in the stator tooth is limited to 1.8 Tesla. Assume, Average gap density=0.4 Wb/m2 Choose main dimensions to give best power factor. Integy Crawler 5-Slot Stator 20 Turn 540 Size Brush Motor INTC29032 Electric. Hayt, William H. (william Hart), Jr, BUCK, John A. Pole pitch: The over hang portion of the coils depend upon the coil span which in turn depends upon the pole pitch. compound generator : Shunt field, A:The equivalent circuit for the DC generator described in the question is shown below: Choose main dimensions to give best power factor. Engineered Electromagnetic Solutions for Critical Applications, 15 Somsen Street | New Ulm, MN 56073 | USA, Technical Requirements for Electrical Machines, Slot Fill and Design for Manufacturability Confirmation, Slot Fill and Design for Manufacturability, Electric Motors in Oil and Gas Exploration, Magnet Retention in Permanent Magnet DC Motors Part I, Magnet Retention in Permanent Magnet DC Motors Part II, Calculate area of one wire, including insulation, Multiply the wire area by the number of wires in parallel and the number of turns per coil to get the total coil area, Square the diameter to get estimated coil area, Multiply the estimated coil area by the total number of coils per slot. ii.When the output power of the motor is 90 hp at a speed of 1732rpm,rotational losses(which includes frictional and core losses) are 10,100W,while copper losses for both rotor and stator total 3700W.Determine the motor efficiency and line current,assuming the motor has a 0.8 pf lagging under these conditions. If the sectional area of the conductors is below 5 mm2then usually circular conductors are employed. Calculate also the speed at which maximum torque occurs. Determine the efficiency of the generator at full load, assuming the iron, friction and windage losses amount to 600W. Fundamental component of EMF induced in stator winding. This represents the relationship of stack length to outside diameter (OD). (d) input power to the stator; (f) the input power factor. 1.5.1The stator current. Current flowing through copper wire coil windings wrapped around an iron core (stator) creates an electro-magnetic field that either opposes or attracts the magnetic field provided by permanent magnets mounted to a drive shaft (rotor). In general, a stator has an outer frame typically made from stacks of aluminum or steel laminations. In our country,the peariform slot was usually adopted as the stator slot of medium and small asynchronous motor,and its size of different machine base number has been used for several decades.In order to study the stator slot size for loss reduction,taking a 5.5 kW motor as an example,the loss prediction model was established based on time stepping finite element method(T-S FEM),and the . (i)Reduced leakage reactance, (ii)Teeth becomes mechanically weak, (iii)Higher flux density in teeth, (b)Slot loading must be less than 1500 ac/slot, (c)Slot pitch must be with in the following limitations, (i)Low voltage machines3.5 cm, (ii)Medium voltage machines up to 6kV5.5 cm, (iv)High voltage machines up to 15 kV7.5 cm. (iii)Increased magnetizing current, (vi)Increased temperature rise. Choose main dimensions to give best power factor. Hence higher value is assumed for low voltage machines and small machines. Copyright 2018-2023 BrainKart.com; All Rights Reserved. SLOT LINER Heat Resistant & mechanically stable insulation papers or thermoplastic materials are inserted in stator slots for preventing coils from shorting from stator core. Heavy duty test stand. The size and number of slots determine how much wire can be contained in each coil, and the wire diameter determines the amount of current that can pass through the coil. Starting with the area of one wire with insulation, which may be available from a magnet wire catalog or handbook, an engineer will multiply the area of that wire by the number of wires in parallel and the number of coil turns to get the total area of the coil. Larger coil bundle sizes can make insertion more difficult. A 3-phase induction motor, 440-V, 50-Hz, 6-pole, delta-connected has the following equivalent-circuit parameters at normal frequency:R1.2 ohm, R'2=0.18 ohm, X1= x'2=0.58 ohm, all per phase values. 3. Out of. When loaded the stator and rotor ampere-. For such slot shapes, the stator tooth is rectangular (Figure 5.5). From the above discussion it can be concluded that multi turn coils are to be used to reduce the cost of the machine. A:The solution can be achieved as follows. The interaction of the electromagnetic field with the permanent magnet field is what produces torque. Do= D + 2hss= 2 dcswhere hssis the height of the stator slot. 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. Area of stator slot:Slot area is occupied by the conductors and the insulation. Stator Parameters There is a direct correlation between aspect ratio and manufacturability. Rounded slots can increase maximum slot fill by 510 percent. These methods are usually specialized to the individual case, but frequently involve an advanced compression system that increases the amount of force on the wire during insertion without damaging the stack or wire. Wedge of suitable thickness (3.5 mm to 5 mm) is placed at the top of the slot to hold the coils in position. The number of turns per phase is based on the pole flux : The airgap flux density is recommended in the intervals: The pole spanning coefficient ot; (Figure 4.13) depends on the tooth saturation factor 1 + Kst. However the following points are to be considered for the selection of number of slots. With segmented winding, the stator is broken up into multiple individual segments based on the number of teeth in the design. These coils are made up of insulated high conductivity copper conductors. If applicable, that estimated coil area is then multiplied by the number of coils per slot. These conductors are suitably arranged along the depth and width of the winding. The stator is laminated to minimize eddy current losses in the form of heat and is divided into multiple slots. Gross length of the stator core: Each turn consists of two times the gross length of stator core. For smaller stators up to 12 in diameter, the most common wire gauges are between 22 and 28 AWG. stator current per phase and suitably assumed value of current density for the stator windings. Adopt a specific magnetic loading of 0.4712 Wb/m2 and a specific electric loading of 23000 ampere-conductors per metre. A three-phase, 3 KV, P=24, 50Hz, Y-connected slip ring IM, Q:A 50-kW, 250-V short-shunt compound generator has 0.06- armature resistance, 0.04- series field. Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail, Design of Electrical Machines : Induction Motors : Design of Stator - Induction Motors |, Open slots: In this type of slots the slot opening will be equal to that of the width of the slots as shown in Fig 10. The star of emf phasors has 18 arrows (Figure 5.3A), and the distribution of phases in slots is shown in Figure 5.3B. Copyright 2018-2023 BrainKart.com; All Rights Reserved. connected, 400-V, 10-hp, 50-Hz,, A:We are authorized to answer one question at a time, since you have not mentioned which question you, Q:4-24- A three-phase, 335-hp, 2000-V, six-pole, 60-Hz, Y- Flux / pole /( width of the tooth at the top section x iron length x number of teeth per pole pitch) As the 2/3. The flux density in the stator tooth should not exceed 1.8 to 2.0 Tesla. First week only $4.99! shunt field resistance of 1 Q, 0.5 Q, Q:A 400 V, 50 Hz, 4-pole, 3-phase, star-connected induction motor has per phase stator One is total diameter, which has a direct relationship to potential slot fill; the other is actual conductor areathe amount of total diameter that is wire, not insulationwhich helps determine how much current can flow through the coil. When a three-phase stator displaced by 120 degrees (in space of 120, Q:A 4-pole, 208 V, 30, 60 Hz, 10 hp, Y-connected SCIM has the following characteristics: The flux density should not exceed 1.8 Tesla. A suitable value of current density has to be assumed considering the advantages and disadvantages. This increases the opening size requirement; an opening dimension of three or four times the wire diameter is common. This increases the difficulty of inserting and compressing the wire and reduces the maximum possible slot fill due to limited space for tooling. From now on, the outer stator diameter will be D'ut = 0.190m. Overview. 1.5.2Estimate the Output torque of the motor under the rated conditions. Sponsored. The coil sets will be connected in parallel once inserted to achieve the same number of wires in parallel. To complicate matters, multiples of pole pairs can be utilized to increase the corresponding number of slots. The machine has the following parameters, referred to the stator, on a per phase basis: However for fractional slot windings number of slots/pole/phase may be selected as 3.5. Number conductors /phase, Zph= 2 x Tph,and hence Total number of stator conductors Z = 6 Tphand conductors /slot Zs= Z/Ssor 6 Tph/Ss, where Zsis an integer for single layer winding and even number for double layer winding. of stator slots, (iv) No. Length of the mean turn is calculated using an empirical formulalmt= 2L + 2.3p+ 0.24 where L is the gross length of the stator andpis pole pitch in meter. Three main structural materials are stator and rotor lamination steel, stator winding, and PMs which are usually NdFeB or Ferrite. 12. iv. So selected number of slots should satisfy the consideration of stator slot pitch at the air gap surface, which should be between1.5 to 2.5 cm. The insertion aid is typically a thin piece of protective plastic that helps guide the wire into the slot; however it reduces the opening space by a small amount and should be accounted for in the design To allow the wire to fit through the opening and leave some space for the guides, the minimum opening should be approximately two times the wire diameter. Privacy Policy, Estimate the stator core dimensions, number of stator slots and number of stator conductors per slot for a 100 kW, 3300 V, 50 Hz, 12 pole, star connected slip ring induction motor. There are many methods to get the geometrical model. If the armature, A:The circuit diagram of DC shunt generator is shown below: As we do have a permanent capacitor motor, the auxiliary winding is always operational. The motors torque output is determined by the voltage applied to the wire, the density of the wire, the number of coils, and the number of coil windings. Stiff wire is less likely to conform to the slot shape and to other wire in the slot. Stators with slot fill percentages of 70 to 80 percent are more challenging to build and may require specialized tooling. The difficulty in this assembly is the design of how the teeth come together and are restrained to ensure that electromagnetic path is closed. However, if Fmtr 4, the number of current paths in parallel has to be increased. Engineers considered increasing the slot size, but instead tried changing the slot shape to a rounded bottom. Sectional area of the stator conductor as= Is/swheresis the current density in stator windings, Stator current per phase Is= Q / (3Vphcos ). The filter media As already discussed in Chapter 4, when dealing with design principles of three-phase IMs, there are basically two design initiation constants, based on past experience: The machine utilization factor CU:D^L The rotor tangential stress f, in N/cm2 or N/m2. 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