Part A - Computing
Assignment Task
Your group is required to submit a motor proposal in the form of a one page outline, an Excel workbook, and a MATLAB script. This outline is to be submitted as a ‘tender' document which goes out to the client.
Contained in the one page outline should be:
- Details on your motor size and structure.
- Summary of calculations including, rotor size, number of turns, number of coils, type of motor, current and voltage specifications.
- You should also include the operating torque and speed that your motor should generate, the expected mechanical output power, and theoretical efficiency. List any sources of loss and the factor that you have allowed for to ensure that your expected results align with the targets listed in the CRA.
In the Excel sheet:
- You are expected to use the Excel sheet to find:
o Motor Constant K
o Resistance of the armature
o Expected speed of the motor in rpm (using terminal voltage)
o Expected torque generated of the motor in Nm (using armature current)
o Ideal mechanical power out
o Expected mechanical power out (include factor for inefficiencies)
- Ensure your sheet is clear, and well-presented and includes at least one example of data validation, custom cell formatting and static cell references.
In the MATLAB script:
- You are expected to use the MATLAB script to find:
o The time to accelerate the motor from standstill to maximum speed; minimum and maximum currents including an applied torque to the motor shaft
o Multiple plots of the speed torque characteristic for the different field densities created by the different permanent magnets
- Ensure your script file is well presented (including useful comments that make your script easy to understand) and that it states any assumptions
- Ensure that you have at least one example of the functions: input, disp, sprintf.
- Ensure that you have demonstrated: multiple lines on a single plot, multiple plots on a single figure, fully formatted graphs including titles, axes labels, colours and legend where appropriate
Part B - Motor
Assignment Task
You are required to construct a commutated DC motor to drive a load, simulated by a generator placed on the output shaft of your motor. You may use any readily available materials.
QUT will provide each group with a DC motor construction kit which, if used correctly, will provide you with all of the parts required to make a functional DC motor. You should look in to ways that you can improve your motor, for example, by improving the quality of your commutator or bushes, improving the strength of your frame, and optimising the position of the magnets. This is not essential, but will demonstrate that you have investigated ways to improve the performance of your motor.
Your magnet selection and wire selection will be based on the results of the calculations you perform in your computer labs.
The motor must be supplied by Direct Current (DC)
- The motor must be brushed/commutated,
- The motor must be supplied by a DC source (Battery, Laboratory Power supply, etc, no active controllers),
- The motor must have a minimum of 3 coils, and a maximum of 8 and must be lap wound,
- The motor may NOT draw more than 5A, and must operate at less than 30V,
- The motor ideally should start without any external assistance
The field MUST be supplied by two permanent magnets
- A set of magnets will be available from the store on S-Block, level 9,
The motor MUST be entirely constructed by you.
- You may get ideas from other, commercially available DC machines, however NO parts must be transferred to your own design
- NO kits of any kind should be used in the motor construction (this includes mechano / lego / jaycar kits), except for the QUT provided kit
- Commercial brushes, and commutators CANNOT be bought, but home made alternatives to those supplied in the kit can be used
1.1 Collection of Motor Parts
All parts are collected from the store on level 9 of S-Block. To ensure access to materials is fair to all groups, a voucher system will be used to prevent groups from doubling up on materials. The vouchers can be found at the end of this document.
Motor Kit
This can be collected once you have formed your group and have your group's voucher signed by your tutor or computer lab demonstrator.
Magnets, Wire and Laminations
These can be collected once you have completed your Excel calculations that will determine your magnet selection, choice of wire, and type of laminations. NOTE: You will receive your wire on a spool. These spools must be returned to the level 9 store before your demonstration day. They must be returned empty, with all wire removed.
1.2 Generator Information
A generator will be coupled to your motor during the test. This will be fitted with a shaft encoder that will monitor the output speed of your motor.
1.3 Knowledge and Application
An oral examination will also be performed at the time of test and demonstration, relating to the operation and design of the motor, directed at individual group members.
The decisions made in building your motor, including material types, winding methodology, number of commutator plates, number of brushes, radius and length of motor, and operational speed/torque characteristics will ultimately determine its use. Your group is to design the motor for a specific application, such as a traction motor, EV drive motor, conveyor belt motor, etc. Your design may be a ‘scaled' version of the real application, however must be constructed to the same considerations that would exist in the real situation. Ensure that your report reflects this application throughout, and that your design choices support the final application.
The criteria for the physical and oral examination can be found on Blackboard.
1.4 Construction
You will NOT be given a lot of guidance as to how you construct your motor, but previous examples will be available to look at in the lectures and tutorials.
The most crucial part of motor construction is the winding of the coils. The copper wire you are given is laminated with an enamel coating, and any damage to this coating could lead to short circuits in your coils, rendering your motor useless. It is important that any sharp edges on the laminations are filed off, and covered in electrical tape to avoid damage to the coils. You must ensure that that each coil is carefully labelled after winding, and tested for short circuits after each coil is wound, so that any problems can be identified early. The size and shape of your coils is important, and will impact upon the performance of your motor. Please ensure you research the impact of the size and shape of your coils on the motor's performance.
IMPORTANT NOTE ON WIRES: As noted above, the wire has a thin enamel insulating coating, so please take care of it, otherwise you will have to obtain replacement wire yourself. As this coating is an insulator, it will need to be removed from the ends that are to be soldered to the commutator. This can be done by sanding, or scraping off the coating at the ends of the wire. If this is not clear, please speak to your tutor.
IMPORTANT NOTE ON MAGNETS: Rare earth magnets are fragile. If you leave them unsecured and close to each other, they will accelerate rapidly towards each other and potentially break. You will only be supplied with one set of magnets, which you are responsible for.
Construction should largely be carried out at home, but tools such as soldering irons are available for use in S902. These are obviously very hot, and it is your responsibility to take care not to burn yourself. There is also a small DIY workshop next to the store on S-Block level 9. This workshop can only be used following an induction with the technical staff, and only 4-5 people can use the workshop at once.
Therefore a maximum of two group members are able to use the workshop at any one time, at the discretion of the technical staff. A service is also available to supply custom laser cut MDF parts. Please discuss the file format requirements with the technical staff on S-Block level 9.
1.5 Testing
The standard dual power supplies available in S-902 may not be suitable for the testing of your motor. There will be two suitable power supplies available from the store on S-Block level 9. These can be booked out for short term loans with your student card, but must be returned as soon as you are finished with them. Test rigs will also be available; information regarding the testing rigs will be announced at a later date.
It is strongly recommended that you test the reliability of your motor before testing to ensure that you achieve the best possible result.
2 Report and Documentation
Only one report is to be submitted for each group of students. The report should consist of two sections, one for computing and one for the motor. The design process should reference the calculations performed in the computing labs. The report should include (however is not limited to);
Part A: Design Phase
- Calculation, planning, materials selection, etc.
- Excel Spread Sheet analysis of field and armature windings
- Expected speed and torque graphs
- Acceleration graphs from MATLAB
Part B: Construction and Testing
- Construction iterations if any,
- Test procedures at various stages
- Quality assurance for winding insulation
- Results of speed, power input, power output, efficiency, operating characteristics and output torque
Review Phase
- Team work breakdown, reflective analysis of the phases, analysis of how concurrent engineering modified your thought process and ultimately the outcome, recommendations, and future improvements.
You may use these headings as a guide, or organise the report as you see fit, it is always refreshing to read unique reports and it certainly puts the marker in a much better state of mind when considering your report.
You may write as much or as little as you see fit, however please note that conciseness is listed on the criteria sheet. Anything over 30 pages may be considered too extensive, anything under 10 might not contain enough depth. Approximately 4000 to 6000 words should be sufficient. Use this as a guide only.