Steady State Operating Curve: Speed UTC Engineering 329

Transcription

1 Steady State Operating Curve: Speed UTC Engineering 329 Woodlyn Knight Madden, EI September 6, 7 Partners: Megan Miller, Nick Rader Report Format Each section starts on a new page. All text is double spaced. The pages are to be numbered. There is to be a footer that has your name and the date on it. If the report is lacking some substantial component, it will not receive a grade.

2 Introduction The purpose of this set of experiments was to render a plot of the steady state operating curve with uncertainty bars. The system, speed, was given an input percentage of full power and a time interval to apply that power. For each input, a plot of time vs. output was rendered. The steady state portion of this plot was used to render the final plot, the steady state operating curve. The objective of all this is to familiarize the students with the equipment, applications, and report formats that will be used throughout the semester. This next section is the Background and Theory. It will describe all of the information required to understand the Procedure section. Logically, the Procedure section follows. This section presents the actions that produced the results. The Results section describes the observations and plots of the results. The Discussion discusses the results and how they are significant. The Conclusions and Recommendations section concludes the report and gives the professor feedback on how the experiment can be improved. The Appendices includes all raw data, references, and other miscellaneous background information. Background and Theory The speed control system is essentially an electric motor that is connected to an electric generator. The motor input is measured as a percentage of the maximum motor power. The maximum motor power produces the maximum motor speed of 1rpm. The steady state operating curve (SSOC) represents the motor speed at a given input power. To generate the SSOC, the system must be run at a constant input until the system reaches steady state. The steady state is when the motor speed stops increasing appreciably. Averaging the motor speed over this steady state time will generate one point on the SSOC. Twice the standard deviation of the motor speed will bracket the uncertainty of the motor speed to within 95% certainty. Procedure The first step in generating the SSOC is collecting the raw data. This is accomplished by running the Speed Control System at 1% input and downloading the raw data in an excel spreadsheet. Now the system is ran with an input 1% higher, and this is repeated until 1% is reached. The raw data in excel is then plotted as output versus time. The plot is used to define the region that the system is at steady state. Once the region is defined, the average output is found over the time interval. Now the standard deviation is found for the average output. Using the input percentage, average output speed, and output standard deviation, a single point with uncertainty bars on the SSOC is generated. This analysis is repeated for other input values, and the result is a SSOC.

3 Describes the engineering background of the lab, including equations and schematic diagrams

4 Results Using the procedure from above, Figure 1 was rendered. The uncertainty bars in Figure 1 do exist, but they are so small that the actual data point is graphically larger than the bar itself. Uncertainty bars are highlighted in red and data points are green to show contrast. Steady State Operating Curve: Speed 1 Output Motor Speed, c (rpm) Input Power Percentage, m (%) Figure 1: Steady State Operating Curve for the Speed Control System. Discussion The slope of the SSOC is constant, so the input and output is linearly dependant on each other. The slope of the SSOC is 17.2 rpm/%. The largest standard variation was found at an input of 1% total power. The standard deviation at this point was 5.9rpm. This represents a variation of only 7.4% of variation with 95% confidence from the average. At higher motor speeds, the deviation does not increase numerically. It only decreases as a percentage of the total motor output.

5 Conclusions and Recommendations Based on the results of this set of experiments, I believe the control system for speed is set up so that the motor input percentage is actually the percentage of total motor output speed. I draw this conclusion, since most variable speed electric motors do not operate from their minimum speed to their maximum speed in a perfectly linear fashion related to the frequency of the driving voltage. In this experiment, a steady state operating curve was found for the speed control system. In order to render the SSOC, several plots were generated from the raw data of several experiments. From these plots, the steady state portion was averaged and standard deviations were found. In working out this analysis, I have become more familiar with the equipment and report formats for control systems. Appendix The following ten plots were used to find the SSOC. Primarily, they were used to identify what selection of the raw data was steady state. The plots are minimized to save space, and the raw list of data can be found in the file exchange. 1% Input 2% Input Figure 2: Plots of 1% and 2% motor input.

6 *"No surprises" means that you can not put some sentence in this section that has not been justified in an earlier section.

7 3% Input 4% Input Figure 3: Plots of 3% and 4% motor input. 5% Input 6% Input Figure 4: Plots of 5% and 6% motor input.

8 7% Input 8% Input Figure 5: Plots of 7% and 8% motor input. 9% Input 1% Input Figure 6: Plots of 9% and 1% motor input.