Design, Construction, and Testing of an Electric Machine Test-bed for Use in Laboratory and

Research Education Trever J. Hassell, Aurenice M. Oliveira, and Wayne W. Weaver

Michigan Technological University - tjhassel@mtu.edu, oliveira@mtu.edu, and wwweaver@mtu.edu

Abstract—Research and education into various methods of improving energy efficiency for electrical devices has become increasingly important to meet future energy needs. Because of this need, an electrical machine test-bed was designed and built in collaboration with a senior design team for the purpose of furthering research and education in the area of power electronics and motor drives. Both the engineering education and research capabilities aspects of this test-bed have an important role in educating engineers with skills to quickly contribute to the power and energy related industry. This paper will discuss the design, construction, and testing of a research quality electric machine dynamometer and test-bed for use in undergraduate and graduate (UG/Grad) education, as well as for research into power electronics and motor control .

Keywords—electrical machine; dynamometer; test-bed; engineering education; power electronics

I. INTRODUCTION Dynamometer systems are used extensively in testing and

verification procedures in various applications relating to automotive, industrial, and manufacturing fields. The advantages of using a dynamometer are to simulate a wide range of loads a system may experience, precise controllability, and unit testing prior to the unit under test reaching the customer. Electrical machine drive systems are used invarying degrees of dynamometer systems for both research and design, and for product validation. In order to investigate some of the latest technology and control techniques for electric machine drives applications, an electrical machine test-bed was designed and built with the purpose for both research into these topics and to compliment undergraduate laboratory course in power electronics and motor drives.

II. ARCHITECTURE AND DESIGN The electric machine test-bed is a collection of various

commercially available and custom made components. It is designed to enable a wide variety of electric machine configurations and applications, as it provides a platform for testing of innumerous projects. The current configuration of the test-bed features two identical 20 HP ABB induction machines in a back-to-back testing configuration. The “dynamometer” is controlled via an ABB (full 4-quadrant) variable frequency drive. The “prime mover” machine is driven from a custom IGBT inverter and is controlled via a dSPACE embedded controller. A Himmelstein compact a compact digital torque meter measures both shaft speed and shaft torque. The power wiring of the test-bed is controlled by a Motor Controller and Safety System Enclosure (MCSSE), shown in Fig. 1. The MCSSE includes a standalone PLC system that controls the power flow throughout the system. The test-bed machine mounting tables were built in modular fashion to accommodate various machine types and size.

While designing the dynamometer test-bed, safety was a top concern. The test cell safety layout is shown in Fig. 2 and shows two zones of safety; the green zone and red zone. These zones are a mental construct used to indicate to the test cell user where the areas of concerns are located. There are no physical barriers, or markings, in the test cell to differentiate the zones. The green zone has virtually no added risk or safety concerns, whereas the red zone requires greater caution. The “green zone” is the intended area for the operator to be during any testing or computer use and has no greater risk due to the test cell components. The “red zone” has significantly greater risk of injury because of the test-bed table, cables and cable trays, and the exposed test cell electrical components; such as the inverter, dc power supply, transformer, dynamometer, and enclosure. These devices have adequate guarding to protect from injury, however the risk is greater around these components. To protect the torque sensor cables, a cable tray was placed on the floor below the workbench. The users should observe caution when working around the workbench. The workbench also has several electrical components that could cause risk of injury and the user should be cautious when working around this. For the mentioned reasons the “red zone” is determined to have an increased risk and increased user caution.

Fig. 1. Testbed Infrastructure Control Cabinet

978-1-4673-5261-1/13/$31.00 ©2013 IEEE

Throughout the entire test cell system there are several

varying power supplies with the majority of power supplies powering the inverter controls and control devices including 5 VDC and 15 VDC powers supplies to power the signal isolation and interface board. The MCSSE has only two external power sources, the “Main Power” source (MPS) (208 VAC 3ph) and the “Control Power” source (CPS) (120 VAC 1ph). Table I lists all of the electrical energy levels present in the system and the rated maximum current carrying (fused limited) ability of the circuit.

TABLE II. TEST CELL ELECTRICAL POWER OPERATION LEVELS

Name Voltage Max Current

Description

Main Powera 208 VAC 3ph 50 Arms Line feeds to Motors

Motor 1 208 VAC 3ph 50 Arms Load feeds for Motor1 (Prime Mover)

Motor 2 480 VAC 3ph 30 Arms Load feeds for Motor2 (Absorber)

Control Powera 120 VAC 1ph 10 Arms

Micrologix, Aux Fans, DC Power Supply

Control System 24 VDC 10 Adc

Test cell I/O, Stop PB, safety relay

a. denotes external power source

A. Electrical Power Stage Design The test-bed architecture was design for two electric

machines “back to back” testing. A one-line schematic is shown in Fig. 4 for the current system configuration. This system configuration allows a lower amount of energy supplied from the building infrastructure. At full load, the energy flow is in a clockwise direction and only the losses in the system are needed from the building power system. The “back to back” testing configuration consists of two identical induction machines that are mechanically coupled together via flexible motor couplings and torque sensor. There is only one source of electrical energy for the electrical machines, a 208 VAC 50 Amp 3 phase receptacle, which is supplied from a power panel from the building infrastructure. This source would supply two “loads”; the magna dc power supply/inverter and an ABB

frequency drive. The Magma dc power supply powers the APS inverter which supplies power, decoupled frequency, to the “Prime Mover” electrical machine, M1. Because the frequency drive operates at a different voltage than the main source power a transformer is needed. The frequency drive would then supply the “Absorber” electrical machine, M2.

B. Control Stage Design

The control state consist primarily of a custom design MCSSE that houses all of the test cell infrastructure controller hardware. The MCSSE includes five 60 A contactors that can control the flow of electrical energy in the test cell. The contactors are controlled via a Allen-Bradley Micrologix controller and a Allen-Bradley safety relay. The safety relay monitors the emergency stop push-buttons using two different electrical circuits for redundancy. If one of the contacts on the ESPB happens to malfunction, the safety relay will detect this and remove the electrical power to the outputs of the Micrologix, therefore opening the contactors, and removing the main power source to the electrical machines. If the safety relay does not detect an issue, the Micrologix controller has control on turning the contactors on and off, based on its user defined program. The advantages of having both devices controlling the contactor operation, is the reliability of the safety relay and functionality of the being able to program using the Micrologix.

The control stage power is derived from a separate power source than that of the electrical power stage. This allows the control stage to operate independent of the power stage being energized. This was a specific design choice to allow for commissioning and troubleshooting purposes. This design choice minimizes the exposure to high voltage and power wiring, when working with solely a control system issue. The power and control stage system level electrical schematics were developed and the MCSSE layout was design specifically to keep the high voltage ac power separate from the low voltage dc safety system power. Fig. 5 shows the MCSSE with the enclosure doors open. The green box indicates the low voltage dc wiring. This is done to minimize any induced voltage on the dc Safety System control circuits which may cause undesired behavior. The presence of the low voltage ac (120 VAC single phase) is necessary to power the dc power supply, Micrologix controller, enclosure ventilation fan, and the inverter heat sink fan, it is located inside the green box (upper right hand corner). This location was chosen to minimize any induced voltage on the low voltage dc circuits.

Fig. 3. Testbed Floor Layout

Fig. 4. One Line Testbed Circuit

C. Test-bed Modularity The test-bed system was design and built to be able to

incorporate various application and configurations. It’s designed is only constrained by the voltage and current levels off 600 V and 60 A respectively. The test-bed electrical machine table, shown in Fig. 6, was design with industry standard “T-slots” for mounting that are spaced with several mounting widths for various electrical machine sizes. The tabletop is also made considerably wider that the current induction machines, to allow for future expansions. The Micrologix controller was also purchase to allow for future expansion of I/O channels and possible future implementation of a Human-Machine interface touch panel.

III. COMPONENT DISCUSSION The test-bed is primarily comprised of off-the-shelf

commercial products. The components are integrated together to form a functional electric machine dynamometer test-bed. The one-line system is classified into two distinct portions; the “prime mover” and dynamometer. TABLE III lists the different subsystems within the testbed as seen in Fig. 7. The top branch of the circuit, or prime mover, consists of the subsystems A and B. The lower branch of the one-line diagram is classified as the dynamometer and consists of subsystems E through F.

TABLE III. TEST CELL MAJOR COMPONENTS

Abbr. Letter

Component Name

A Dc Power Supply B Dc-AC Inverter C Induction Machines D Motor Coupling Assembly E Isolation Transformer F Variable Frequency Drive G Controller Station H Control Signal Isolation and Interface

A. Prime Mover Components The “prime mover” components consist of the dc power

supply and inverter. These two components allow for control over Motor 1 via the dSPACE embedded controller. The dc power supply converts the three phase voltage supplied by the building infrastructure into a dc potential, which then feeds the 3 level inverter. The inverter uses common control switching techniques such as volts per hertz, field oriented control, and direct torque control to send the appropriate voltage and current waveforms to Motor 1.

The dc power supply is manufactured by Magna-Power Electronics and is available in a variety of input and output configurations. The model used in test-bed is a TSA400-36 and has a 240 volt, 3 phase input. Its nominal output power is 15 kW with a max dc output of 400 V and 36 A. It has three modes of operation; Normal, constant voltage, or constant current. For the “Normal” mode the TS series power supplies can be configure for control by rotary mode input, local sensing, internal control, and external control. With this configuration, the operator can select either a constant voltage or a constant current output using the front panel controls. The mode is determined by the limits of the voltage or current settings. During operation whichever limit is lower for that particular operating point it will determine the operation mode, either constant voltage or constant current, that will be governing the control. For the test-bed application the dc power supply is configured to be constant voltage control by setting the current limit to the maximum value. The embedded controller then sends an analog signal to the power supply governing the dc output voltage. However one major drawback

Fig. 7. Test-bed System and Component Integration Overview

Fig. 6. Dynamometer Test Bed Table

Fig. 5. Testbed Infrastructure Control Panel Layout

is the dc power supplies inability to sink current and absorb power from the electric machine.

The inverter can be configured as either dc to dc power converter or a dc to ac single/three phase inverter. It main function is to power and control the “prime mover” machine. The unit is manufactured by Applied Power Systems, Inc. The inverter, part number IAP75T120, is a standard IGBT sixpack configuration consisting of 6 IGBT arranged in 3 phases, each containing two IGBTs. The inverter can accept up to a 850 Vdc input, operates at switching frequencies up to 20 kHz, and has a maximum phase current of 75 A. It features built protection systems for output over-current, input over-voltage, heatsink over-temperature, control under-voltage, and short circuit protection. It also features opto-isolated (fiber-optic) gate drive and fault signal output for electrical isolation and noise immunity.

B. Dynomometer Components The dynamometer components consist of the isolation

transformer, variable frequency drive, and the second induction machine, Motor 2. The variable frequency drive (VFD), was donated from ABB Automation and Power based out of New Berlin, Wisconsin. It is intended to provide the load torque in the dynamometer system. It is an ultra-low harmonic (ULH) VFD, which minimizes the amount of harmonics injected from the grid or power supply. The VFD features insulated gate bipolar transistor (IGBT) controlling the supply side of the drive line connections to the dc link, known as an active front end (AFE). This is in contrast to the conventional diode bridge used in other VFD systems [1]. The AFE permits the ABB VFD to control the line current to sinusoidal waveform and the built in harmonic mitigation eliminates the need for additional, expensive equipment like transformers or line reactors. The AFE also ensures that the drives meet the harmonic distortion standards set by the IEEE 519 1992 standard. The ABB VFD also features Direct Torque Control, and open-loop dynamic speed-control with accuracy matching ac drives using closed loop flux vector control, Start-up Assistant estimates motor parameters by the user entering nameplate info, and Adaptive Programming.

The isolation transformer is needed because of the different potentials between the building supplied voltage level (208 Vac) and the required input voltage of the VFD (380-500 Vac). The transformer was purchase to be configured as a 30 kVA step-up, step-down, or isolation transformer. The ability to use the transformer in any one of these three configurations allows for future flexibility and varying electric machine voltage potentials while added only approximately 25 % more in purchase costs.

C. Electric Machine and Coupling Components The electric machines used in the current configuration are

20 HP dual winding induction machines; wired for 230 VAC or 480 VAC. They have a rated frequency of 60 Hz, rated speed of 3515 RPM, and a full load current of 22.5 A/45.0 A depending on their wiring configuration. Unfortunately there was no documentation for this donated equipment, so only nameplate information is available. Further machine values and parameters are discussed in section IV.

The motor coupling assembly is comprised of a torque sensor and two flexible coupling units as shown in Fig. 8. The assembly is a “mechanically floating” system. This means there is no support to the sensor holding off the test bed. Excluding the shafts, the only means of mechanical connection is strap (cable) used to mechanically “ground” and keep the sensor from spinning with motion of the shafts. The only force the mechanical “grounding” strap would need to provide is the frictional bearing force of the sensor.

The torque sensor is commercially available unit purchased

from S. Himmelstein and Company, which specializes in torque sensors of all type. It has a max continuous torque rating of 113 Nm and 226 Nm overload rating. It provides both shaft torque and speed information to the embedded controller from an external signal condition unit purchased with the sensor.

The torque sensor used is in conjunction with flexible couplings manufactured by Zero-Max. Theses couplings are intend to minimize any misalignment in the horizontal direction which would translate to axially torque that could possible damage the torque sensor. The flexibility comes from the composite discs that are a “clover” shape and are made of laminated, flexible sheets. The same flexible coupling units can be order with a variety of input and output shaft sizes, lending it to be appropriate with future configuration flexibility.

D. Test-bed Operational Controls The current test-bed operation control is comprised of three

independent interfaces. The inverter embedded controller, which sends the control signals to the inverter unit, is an ACE 1104 unit supplied from dSPACE. This system was chosen for its known behavior in laboratory classes and its relative ease of use. This controller features two digital signal processors (DSP). The “primary” DSP performs the control algorithm execution therefore performing the majority of the calculations, and executes at a rate of about 100 µs. The other DSP, or “Slave” DSP, controls the switching action sent to the inverter via pulse width modulation (PWM). The slave DSP can operate at switching frequencies in excess of 100 kHz. The DS1104 and breakout box features 8 ADC analog inputs (4 multiplexed, 4 parallel), 20 digital input/output (I/O), 8 channel DAC analog outputs, two DSP, serial communication port, and digital incremental encoder interface.

Fig. 8. Torque Sensor and Flexible Coupling

The VFD has several options for user control input such as front panel keypad, and using a fieldbus adaptor that can communicate on various industry communication protocols. For the test-bed configuration, the VFD communicates via Modbus RTU receiving its commands using LabVIEW from the test-bed computer. This configuration allows the VFD to be controlled through the common test-bed computer. From the user station, the VFD can be turned on/off, reference torque, and reference speed can be commanded.

The test cell infrastructure controls was designed to be a standalone system, independent of the VFD and inverter control systems. The test-bed infrastructure controls what power stage components are supplied the primary 3 phase power from the main power source. The test cell infrastructure controls consist of the power wiring, fuses, contactors, and a programmable logic controller (PLC). Based upon the user provided control inputs, the PLC decides the states of the outputs. Example of these control inputs are contactors, the safety relay, start/stop pushbuttons, fans, and indicator lights. The outputs of the system are the 3 phase power contactors as well as a few indicating lights. The high level control scheme of the test cell safety system puts the system in one of five states; “Ready”, “Enabled”, “Powered”, “ON” and “Fault”. These states dictate what, if any, combination of contactors and indicating lights are on.

IV. SYSTEM PARAMETERIZATION AND PERFORMANCE To utilize this system as an educational platform, its

behavior must be observed and quantified. There are several unknown areas, component efficiency, system response, and electric machine parameters that needed to be understood and characterized. These areas include induction machine parameter estimation, component operation efficiency, and system response data.

To employ any type of modern electric machine control techniques such as FOC or DTC [2]-[3], the induction machine parameters needed to be determined. Precisely knowing these parameters allows for accurately modeling and designing the control algorithms is used to command the system. The method used to derive the equivalent electrical machine parameters listed in TABLE V. Several tests were performed to estimate the parameters of the ABB 20 HP induction machines; No-load and blocked rotor tests. These tests were conducted according to [4]. The no-load test obtains the number of pole pairs by comparing ratio of the electrical frequency over the mechanical frequency are various values, up to rated speed. In addition the machine was operated at rated voltage and rated speed, and the data in TABLE IV was obtained.

TABLE IV. NO-LOAD TEST DATA

L-L Voltage (Vrms)

Line Current (Irms)

Freq. (Hz)

Speed (RPM)

Real Power

(W)

Apparent Power (VA)

220.04 7.463 60.044 3590 723 2808

TABLE V. MACHINE PARAMETER ESTIMATION SYMBOLS

Symbol Name Value Unit

Rs Stator Resistance 150 mΩ Rr Rotor Resistance 2.977 mΩ Lls Stator Leakage Inductance 303.57 µH Llr Rotor Leakage Inductance 202.38 µH Lm Magnetizing Inductance 42.7712 mH Np Number of Pole Pairs 1 -- J Moment of Inertia 0.0526 Kg-m2

The block rotor test involves a rotor blocking device that prohibits the rotor to spin. Since no commercially available device was available for the induction machines used, a custom rotor blocking fixture was designed and built. The blocked rotor test applies 25% rated frequency and rated line current. For this particular system the current test was about 90% of rated current due the lack of current source ability of the dc power supply. The blocked rotor data was collected as shown in TABLE VI.

TABLE VI. BLOCKED ROTOR TEST DATA VALUES

L-L Voltage (Vrms)

Line Current (Irms)

Freq. (Hz)

Speed (RPM)

Real Power

(W)

Apparent Power (VA)

16.68 40.301 15 0 719 1148

V. BENEFITS The test-bed was built to meet the demand for an easily

configurable platform to further research in the areas of power electronics, motor drives, and electric vehicle propulsion systems. Hence, it was built to be flexible in order to adapt to a variety of areas and be easily transformed to any future research or educational need.

A. Direct Project Interaction The test-bed was built with a relatively low cost which was

accomplished by incorporating the design and construction tasks into graduate and undergraduate students’ project work. By integrating senior design, faculty funded project and industrial partnership, the overall project cost was reduced, while increasing the direct student exposure to concepts they usually have no hands-on. Our industry partner ABB Inc. Medium Voltage Drives, Research and Development group donated several key components used in the test-bed.

The project team consisted of a graduate student and three undergraduate students. The team was led by the graduate student doing research in the areas of motor drives and electric machines. The undergraduate students received Capstone Senior Design credits for this project. The team members received numerous benefits from involvement with this type of capstone project that they would not get in a traditional senior design project. The first major benefit was working on a real collaborative multi-disciplinary project among faculty, undergraduate and graduate students. They also learned how to work with real system design requirements. Students were also exposed to industry tool such as CAD design and layout,

dSPACE embedded controller, National Instruments LabVIEW VFD control, PLC programming, Allen-Bradley Micrologix Program, communication (ModBus) integration, sensor integration, fault detection, OSHA safety standards. The senior design students will be able to apply in their career the technical knowledge from the use of the development tools they were exposed to during all phases of the project as well as some experience with complex system level problem solving.

B. Research Potential There are many research topics that the test-bed is intended

to be utilized. These topics include electric drive systems, electric or hybrid-electric vehicles propulsion, power electronic converter principals and topologies, and ac micro-grids components. Investigation into high performance machine control algorithms is a clear example of research opportunity. The initial test-bed system was characterized using a lower performance control algorithm, slip control. A higher performance induction machine control algorithms allow for a starting point in the machines controls research. This research topic is applicable to industrial companies in Variable Frequency Control of electric machines. Some applications are for Pump stations for both mining properties and municipals, fan control systems for HVAC.

The test-bed would also serve to investigate areas in an electric vehicle propulsion system. The prime mover described in Section III.A would be used to emulate an electric vehicle propulsion system. The current AC machine topology (asynchronous 3 phase induction machine) is the propulsion system for the Tesla Roadster [5]. Another electric propulsion topology utilizes an AC synchronous machine, specifically AC permanent magnet, is currently used in the Chevrolet Volt [6] and Nissan Leaf [7] propulsion systems. Given the modularity design of the testbed system, it could easy be modified to replace the prime mover machine with an AC permanent machine and emulate this propulsion topology.

The current system configuration has some limitations, specifically two quadrant machine operation. For full vehicle simulation the dc power supply would need to be replaced by a battery pack, because the current dc power supplies inability to sink current. If propulsion only drive cycle scenario, no regenerative braking conditions, a simulated battery voltage/current profile from the output of the dc power supply could be emulated. The current inductions machines could be used as common electric machine types for automotive propulsion systems or they would either be replaced with differing machines, as needed by the EV propulsion system architecture.

To utilize the test cell for a three phase ac MicroGrid, it would need to be modified according to the combination source and load desired. Minimal testbed hardware configuration would need to be changed, however the test cell infrastructure controller scheme would require substantial development, most notably if the test cell was not used as a machine type load. This changed relates to the order and timing of the contactors that control the power flow in Fig. 4.

The test-bed can be configured for an typical industrial motor drive type application by replace the dc power supply

with a 3 phase hex-bridge converter to converter the 3 phase line voltage to a dc bus voltage. This approach is known as an Active Front End (AFE) and is common in most modern motor drive systems. The AFE configuration allows for increase input power quality [8]. This would require a slight hardware configuration change however the control scheme and system signal would need to be altered significantly. Using an AFE over the current DC power supply would also have the added benefit of allow for current sinking ability and regenerative braking applications.

C. Undergraduate Laboratory Experiences The incorporation of this test-bed into the curriculum of the

power electronics and motor drives laboratory was one of the main objectives of the test-bed. The motor drives lecture and lab introduces engineering students to various types of electric machines and their control algorithms. Fig. 9 illustrates the actual academic bench top system. This bench top system has the same flexibility of changing to various machines types, both AC and DC. The advantage to this bench top system is the safety in size and reduced complexity. With this bench top system students study the major machine topologies such as DC machines, AC synchronous machines (permanent magnet), and AC asynchronous machines (induction).

Fig. 9. Academic Motor Drive System

One common topology used throughout industry is the induction machine. The motor drives lab focuses several weeks on this particular machine, where students characterize its behavior. However, the system which students perform their experiments is significantly different in power level and setup compared to an actual test electric machine testbed seen in industry. This is done to reduce the risk and complexity the students would experience and allow them to place focus to fundamental concepts.

The different level of complexity can be easily observed by comparing the electric machine test-bed (shown in Fig. 1, Fig. 5, and Fig. 6) to the academic bench top system (shown in Fig. 9). Even though the reduced complexity is beneficial for the students start learning these topics, many students commented that they do not know how the academic systems correlates to system they will see in an industrial setting. Exposure to the test-bed gives students an example of an industrial type setup. To reduce the complexity and safety the bench top system is at a very low power level and uses measurement data from the power electronic converter board. Using these on board sensor

circuits is not as accurate or consistent as separate measurement equipment. While this simplified method of data collection works for the educational objectives, it leaves a gap between how similar tasks are executed in industry. The test-bed also exposes students to industry quality data acquisition and measurement devices. The test-bed equipment consists of Yokogawa power analyzer, LEM current sensors, Himmelstein torque/speed sensor, APS power converters, ABB variable frequency drive, and Tektronix Mixed Domain Oscilloscope with smart voltage and current probes. This equipment exposes engineering students to the types of power and data acquisition device they will encounter in their engineering career.

This test-bed serves as an excellent platform to introduce students to industrial grade dynamometer systems and measurements devices. It relates the concepts the students are learning in the classroom to an actual industrial system. It also introduces students to think about subsystems within a more complex test-bed and how these subsystems interrelate to each other, which is crucial for systems engineers [9]. During the last lab experiment for the motor drive class, students solely focused on the electric machine test-bed system. Basics of energy flow and conversion principals are discussed in relation to their newly gain knowledge of motor drive concepts, obtained during the semester recitations and lab. Students also performed the same system performance test outlined in Section IV. This allowed them to see and interact with typical industrial type equipment.

The power electronics lecture and lab introduces engineering students to different types of electric energy conversion principals and topologies, and their control systems. Starting in Fall 2013 to the test-bed will be used to demonstrate some of the difficult topics including dc to ac conversion, Pulse Width Modulation, and power filtering. The test-bed will be used to discuss on how these topics interrelate within a system. Similarly to the topics discussed in a previous motor drives course, the test-bed will be used to focus an entire lab session to discuss the energy conversion process. These concepts are demonstrated and discussed using the inverter feeding electric energy to prime mover electric machine. In addition, students can see a direct use of the topics taught in lecture in a typical industrial application. In addition, the various electrical energy voltage and domains (discussed in Section II) will be presented demonstrating how these individual topics interrelated within the test-bed.

VI. CONCLUSIONS A research quality test-bed was designed and constructed

with emphasis placed on flexibility and integrated modular systems. This allows to easy adaption to future projects and research topics. The test-bed was also tested to demonstrate its functionality and to define a baseline for its operation. Its dynamic and steady state characteristics where also defined along with the characterization of the current induction machines. We discussed the use of the test-bed in various research areas that could be utilized based on current configuration or with some modifications. In addition to serve for research purposes, the test-bed is a very useful platform for engineering education in power electronics and motor drives,

exposing students to industry typical applications and configurations.

ACKNOWLEDGEMENTS The author would like to express their gratitude to ABB

Inc., Medium Voltage Drives, Research and Development group located in New Berlin WI for donating several key components used in the testbed.

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