Design and Analysis of Electrical Machines and Drives: Coursework Specification 2. Introduction to FEA Modern electrical machine design is heavily based on Finite Element Analysis (FEA) software. A number of commercially available packages exist based on the same working principle: the machine is split into a large number of small elements, and the magnetic and electric fields are analysed within each element. The machine geometry is drawn in a CAD like environment, and any machine geometry may be analysed. For more standard machine design, it is possible to use simplified versions of FEA,
Design and Analysis of Electrical Machines and Drives: Coursework Specification 2. Introduction to FEA Modern electrical machine design is heavily based on Finite Element Analysis (FEA) software. A number of commercially available packages exist based on the same working principle: the machine is split into a large number of small elements, and the magnetic and electric fields are analysed within each element. The machine geometry is drawn in a CAD like environment, and any machine geometry may be analysed. For more standard machine design, it is possible to use simplified versions of FEA, where the user selects the machine geometry from a library of pre-drawn options. This type of software can be used as a design tool, and in this coursework we are going to use Motor-CAD, as shown in Figure 1. A tutorial of how to build and simulate a brushless PM motor is attached in Modules-Assessment 2 on canvas for your reference. Figure 1. Default Brushless PM Motor when you open Motor-CAD for the first time.3. Cordless Drill – Coursework Scenario 3.1 Specification: Cordless electric drill The manufacturer has received complaints about the design of the drill, many of which say they feel it is underpowered and unable to be used for a full days work. So you have been tasked by the manufacturer to increase the peak torque of the machine so that it feels better to use, along with an increase in machine efficiency to extend the battery life of the product. The specification of the original product is shown in the Table 1 below. Table 1. Specification of the original product Manufacturer DeWalt Model DCD778L2T-SFGB No-load speed 0-500/1750 rpm (after gearbox) Power 340 W Drill Max torque 65 Nm 3.2 Dimension measurements Six photos below show the measurements of the original motor in the drill, which provide you a reference of geometries and winding connections when you start to build the original motor in Motor-CAD. The motor has 6 slots and 4 poles and is powered by a three-phase six-step inverter. The magnets are embedded in the rotor, so it is an interior permanent magnet machine. The wires have an area of 0.28____2 with 33 turns per coil. And the coils are connected in a delta configuration with 2 parallel paths.3.3 Experimental measurements Here are some useful testing results that you will use to compare with when you had a motor built in Motor-CAD. 1) After a testing in lab, the original motor was found to output a peak torque of 0.667Nm at 4067rpm. At this speed and torque the supplied line current had a peak value of 90A. 2) The DC link voltage supplied to the inverter was 18V. 3) The back EMF was found to have a peak of 8.5V, when unloaded, at a speed of 10000rpm before the gearbox.4. Coursework: Redesign of a motor Your project is to develop the design to the manufacturers new requests, the only stipulation is that the design must be a brushless permanent magnet machine driven by a six-step inverter. It is helpful to model the original motor in Motor-CAD to see its operation. Any aspect of the motor can be altered, along with any topology offered in Motor-CAD (i.e. surface mounted, buried or bread loaf), the choices of how you will alter the original design are yours however the overall dimension of the motor (i.e. Outer diameter and axial length) must remain mostly unchanged. 4.1 Design criteria The ideal motor is light, efficient and cheap. Machine design is all about compromise, for example an efficient machine is likely to be more expensive. One way to get the best design based on both cost and efficiency is to give these criteria relative importance e.g. if efficiency is more important than cost, the designs can be ranked based on a weighting of 80% efficiency and 20% cost. e.g. design score = 0.8*efficiency (per unit)+0.2*cost (per unit) This is only a suggestion you can use your own depending on what you deem to be most important. The criteria typically used in machine design: Mass (kg) total mass of machine magnet mass (kg) total mass of magnets cost () based on mass of material efficiency volume (m3 ) Useful figures for cost and density are given in Table 2. Table 2. Cost and density of some materials commonly used in electric motors cost density /kg kg/m^3 copper 3.76957 8940 steel 1.16 7600 NdFeB 125.1282 7500 Ferrite 5.504834 4900 In you project you can use these ratings to guide design choices. You will have to propose and justify a method of incorporating these weightings into your design process. 4.2 Report and Marking Scheme A number of sample design reports for completely different applications have been provided on Canvas. Do not copy the format, method or layout, but they might help you plan your own work. You must demonstrate that you have done some design work and you understand the results of the simulations. Your design must meet the required torque. The overall breakdown of marks is 20% Report: Style / presentation / quality of language60% Investigation: Quality of investigation / data gathering / research / assessment of effort 20% Design: Selection process / quality of final design (from inspection of uploaded Motor-CAD model) /report conclusion The report must include the following technical sections (marks provided): A target specification for your proposed design, including the torque you wish to achieve, speed, target mass and new efficiency, based on the original motor provided. (/10) A preliminary analytical design study (e.g. suggested pole number, magnet height, back iron depth, tooth width etc.) using sensible assumptions/limits supported by relevant calculations as to why the design parameters were chosen (/10) The use of Motor-CAD to investigate a number of potential designs for your application and analysis of these designs. (/20) Evidence of a design study (e.g. pole number verses performance, motor type verses performance, magnet type verses performance). (/20) A discussion on how you have selected your final design based on the conflicting performance criteria, and why you may have disregarded others (/10) Relate your final design to the analytical machine theory explaining why your changes have resulted in increased performance. (/10) Summary details of the final design including a comparison of your re-design to the original motor, and upload the Motor-CAD model to Canvas (/10) Referencing literature, it is acceptable to base designs on those found papers etc. (e.g. papers from IEEE Xplore) (/10) If your device requires a gear box, please state its ratio but you do not need to design it. The report must be less than 2000 words / 10 pages (excluding title / contents page, appendices and references
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