Linear Induction Motor (LIMO) Modular Test Bed for Various Applications

Transcription

1 Linear Induction Motor (LIMO) Modular Test Bed for Various Applications ECE 4901 Senior Design I Fall 2013 Fall Project Report Team 190 Members: David Hackney Jonathan Rarey Julio Yela Faculty Advisor Professor A. Bazzi Office: ITEB 331 Phone: (860) bazzi@engr.uconn.edu University of Connecticut Department of Electrical and Computer Engineering 1

2 TABLE OF CONTENTS I. INTRODUCTION 1 II. III. IV. BACKGROUND STATEMENT OF NEED PROJECT DESCRIPTION V. PROJECT DESIGN 5 VI. PROJECT PHASES AND MILESTONES 6 VII. BUDGET VIII. PROJECT COLLABORATORS 7 8 2

3 I. INTRODUCTION A linear induction machine will be designed and fabricated to be used as a modular testing platform for multiple applications. Up to four stators will be used in conjunction with two variable frequency drives (VFD) to supply the flux required to move the rotor of the machine and provide precise movement control. The rotor, stator and rotor guide will be adjustable so the user can change air gap and other geometric parameters of the machine. The user will be able to remove stators as needed to run the machine with one or two pairs of stators. Rotor material can be removed and replaced easily to allow for testing of different materials and rotor designs. Optical linear encoders will supply feedback to the control loops of the VFD s to allow for accurate speed, position and force control. The two VFD s will communicate through Modbus protocol and will be controlled through a LabVIEW GUI which will convey pertinent information the use and allow for intrinsic control. II. BACKGROUND The history of linear motors date back as far as the 19 th century with the work of Charles Wheatstone in Great Britain. Charles s linear reluctance motor and Nikola Tesla s invention of the induction motor led to the first linear induction motor (LIM) in 1905 by the German inventor Alfred Zehden. The linear induction motor is an AC asynchronous motor which provides a rectilinear motion in contrast to a rotational motion found in conventional motors. A major advantage of linear motors is the capability to produce a direct thrust without the need of converting rotational energy into translational energy. Disadvantages linear induction motors mainly consist of low efficiency as compared to a rotational induction motor. Linear movement is required for many applications such as industrial robots, liquid metal pumping, machine tools and propulsion systems. An interesting application is the Electromagnetic Aircraft Launch System (EMALS) which being developed and is currently on the second phase of testing by the United States Navy. EMALS is designed to launch aircrafts off carriers using a linear induction motor to replace the conventional steam pistons. Another example is the use of linear induction motors to drive conveyor belts. They can be found in factories, coal mines, and shipping facilities where movement of merchandise and heavy material is needed. They provide economical and cheap maintenance to the owners and have adjustable speed. These are just a few examples, as there are unlimited applications for a linear induction motor. III. STATEMENT OF NEED In order to begin modeling and developing linear induction motors for different applications, it is necessary to have a modular test bed. To allow for maximum experimental utility the setup will be designed to allow for different rotor materials, highly accurate sensors to provide a fast response, and acceptable motor efficiency. Position sensors will allow us to monitor the position of the rotor and adjust VFD output to adjust rotor movement. The modular LIM test bed will allow customization in order to accommodate several applications and designs. Some of the designs include air gap manipulation, stator tooth, and a quad stator topology. We will also interface LabVIEW with a variable frequency drive (VFD) to control the speed and force of the LIM. 3

4 IV. PROJECT DESCRIPTION The proposed project will be design with the main goal of having a high degree of modularity. The linear induction motor test bed will have an interchangeable rotor, specific rotor guides, variable stator designs and the ability to adjust the air gap. These adjustments will allow us to test or implement different ideas in order to improve efficiency and control. For example, we can observe the effect on position by changing the rotor material from copper to silver. Another example is observing the effect of different stator teeth design topologies or even test out new topologies proposed by the team. The linear induction motor test bed will use a rail system to support the rotor and provide a smooth movement. An example of a rail system that will be used is shown in Figure 1. This rail system will slide back and forth with the movement of the rotor. Either long or short rotors can be used on this rail system. The team will create a rail system with maximum size of 6 feet. Table 1 shows the summarized technical specifications of the project. Fig, 1. An example of the rail system. V. PROJECT DESIGN The design of the linear induction motor is largely dependent on a combination of two items. First, the team has performed an extensive literature review surveying designs of linear induction motors for a multitude of applications. The purpose of this literature review is to determine baseline parameters for this design so that they may be optimized. The second determining factor in the design is the testing and optimization of the design using a magnetic simulation program. The program the team has chosen to use is made by ANSYS Maxwell and trial licenses of the program have been granted through Professor Bazzi. Testing using ANSYS Maxwell is currently underway and when finished the design will be sent out for manufacturing. 4

5 As shown in Table 1, many of the baseline parameters for the design are chosen but still need to be evaluated using ANSYS Maxwell. Preliminary parameters such as stator, rotor and rail system length will most likely not change. However, certain parameters such as stator stacking depth and width as well as stator tooth design will be simulated to optimize the design before manufacturing. These are crucial to the efficiency of the machine and need to be evaluated. The rail system will be developed in the future and will look similar to the example shown in Figure 1. The control aspect of the design is another important piece of the project. As mentioned previously, the linear induction motor will be controlled via one or two Yaskawa A1000 VFDs. Each VFD is capable of controlling two stators and in the case of a quad-stator design, two VFDs will be necessary. The VFDs will communicate through Modbus protocol and will be controlled through a LabVIEW GUI. Optical linear encoders will supply feedback to the control loops of the VFDs to allow for precise speed, position and force control. The team has decided to use Avago linear encoders for this project as shown in Figure 3. Fig. 2 Image of common Yaskawa drives Fig. 3 Avago linear encoders 5

6 The linear encoder will observe the speed of the rotor and determine its position. Encoder tape will be affixed to the rotor so that the linear encoder can "see" the position change of the rotor. An example of a linear encoder tape is shown in Figure 4. The encoder tape has precisely marked divisions which will allow for precise position and speed control of the linear induction motor. The ends of the stators will also have LEDs and sensors to ensure the rotor is not ejected from the stator. Table 1. Technical specifications Mechanical Specifications Stator Length ~ 15 inches Stator Stacking Depth ~ 2.5 inches Stator Width Depended upon FEA Stator Material M19 Electrical Steel Stator Tooth Shape Rectangular (Open slot) Rotor Length ~ 20 inches Rotor Material Aluminum Rail System Length < 6 feet Electrical Specifications Input Voltage to VFD Three-phase 208V Input Frequency to VFD 60 Hz Power < 2.2 kw per VFD VFD Output Frequency Range Hz Fig. 4 Linear encoders tape 6

7 Figure.5 Block diagram of the quadstator control system 7

8 Figure 5 shows a block diagram of the control setup of the proposed topology quadstator. The three-phase AC source is connected to a bus which connects to two the VFD. The VFDs are then interfaced with LabVIEW for control operations. The output of the VFDs are connected to the stator pair (in this setup) to provide a controllable voltage and frequency value. An encoder is connected to the rotor and back to the two VFDs to provide position control. A double sided linear induction motor (DSLIM) as shown in Figure 7 can be implemented as shown in Figure 5 block diagram but without the need of the extra VFD and a stator pair. Figure 6 shows the preliminary parameters for a single stator that will be simulated in ANSYS Maxwell. Once simulations results are achieved, the parameters will vary in order to provide the best results. Figure.6 Preliminary parameters for a single stator. Figure.7 DSLIM diagram. 8

9 VI. PROJECT PHASES AND MILESTONES The project has been divided into multiple stages of development. The two main delineation points will be the fall and spring semester, however, we will work on the project over the winter break. The main focus of September and October will be literature review and commercial product research of traditional induction machines and for potential VFDs and corresponding controls. CAD designs of the linear induction motor will be created between October and November. A large amount of time will be spent on the design and simulation of the linear induction motor using ANSYS Maxwell during November and December. As mentioned previously, ANSYS Maxwell will allow for thorough modeling of the linear induction motor to understand its operation and essential parameters. This information is critical to the success and further progress of the project. The same time slot will be used for sensor research to determine effective control methods for the motor. The VFDs will be ordered by the end of October or early November and the order for the stator, rotor, and sensors should be done by late December. Bridging December and January will be the graphical user interface (GUI) work which will be implemented with LabVIEW as well as control testing. January will also be spent assembling the linear induction motor after required parts come in. This will leave the last three months of the spring semester open for machine optimization, application integration testing and to take care of any emerging task from last semester. Figure 5. Timeline of the work to be done on the linear induction motor VII. BUDGET The budget will be provided through our advisor Professor Bazzi. Table 2 below shows a breakdown of the linear induction motor cost estimate. A large portion of the budget will be spent on the two Yaskawa A1000 VFDs to be implemented in the design. Figure 2 above is an example of common Yaskawa drives. They will cost approximately $1,000 each for a total of $2,000. The 9

10 next largest cost incurred will be the manufacturing of the stator at an estimated $1,000. It is very likely this figure will change depending on manufacturer and stator parameters. The rotor and rotor guides for different applications are estimated to be $200 each and the wiring necessary to wrap to stator teeth will be approximately $150. Various sensors to monitor position of the rotor will and corresponding electronics will be around $300 and interface boards to tie these components together are estimated to be around $200. This is a total preliminary budget of $4,050 and is subject to slight modification as the project progresses. Table 2. Cost of the linear induction motor modular test bed Name Approx. Cost (2) VFD $2, Stator $1, Rotor $ Rotor Guides $ Wire $ Sensors and Electronics $ Interface Boards $ Total $4, VIII. Project Collaborators University of Connecticut Electrical and Computer Engineering David Hackney o Senior Design Team Member o Electrical Engineering Major o david.hackney@uconn.edu Jonathan Rarey o Senior Design Team Member o Electrical Engineering Major o jonathan.rarey@uconn.edu Julio Yela o Senior Design Team Member o Electrical Engineering Major o julio.yela@uconn.edu Professor Ali Bazzi o Faculty Advisor o bazzi@engr.uconn.edu Illinois Institute of Technology (IIT) Electrical and Computer Engineering Professor Ian Brown o ibrown1@iit.edu Sources [1] Wells, J.R.; Chapman, L.; Krein, P.T.; Walls, T., "Linear induction machine design for instructional laboratory development," Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference, Proceedings, vol., no., pp.319,322,