DC Motor Building Assignment

Assignment Description

The purpose of this assignment is to give you practical experience with DC motors. The DC motor assignment consists of two parts. The first is a computing task that will help you design and simulate your DC motor prior to construction. The results of this analysis will be used to make important design decisions for your actual motor. The second part is to construct a DC motor that will be demonstrated in Week 11.

This assignment will be completed by GROUPS OF FIVE STUDENTS. You may select your own groups, which will be done using the Blackboard groups system.

Knowledge Requirements

Before you are able to complete your DC Motor Assignment you will need to know:

- DC motor parameters and how these affect motor performance.

- How DC motors are physically constructed.

- How to test DC motors to assess performance.

- How to use Excel and MATLAB.

Part A - Computing

1 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 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, formatted graphs including titles, axes labels, colours and legend where appropriate

Part B - Motor

1 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.