An electric machine is a general term for machines using electromagnetic forces; it is a device that converts mechanical energy into electrical energy (Generator) or vice versa (Motor). Electric machines also include transformers, which do not make conversion between mechanical and electrical form and do not have any moving parts but they convert AC current from one voltage level to another voltage level keeping the same frequency. The Test bench, proposed here by De Lorenzo, is a multipurpose bench for the study and the deepening of Eurolab (0.3 kW) and Unilab (1.1 kW) laboratories. It is composed of a prime mover controlled by an inverter, a user interface with data acquisition software using the Modbus protocol and developed in LabView, an HMI gateway allowing the use of the prime mover as drive or load and instruments that carry out mechanical as well as electrical data. Beside this basic bench, the client can choose from a complete list of machines and accessories what he needs to study in depth. It is recommended for high schools and first years of university.
The DL EM-TEST is a multipurpose bench for the study and characterization of the Eurolab series (0.3
kW) and Unilab series (1.1 kW) electric machines using an automated test approach.
The system is composed of the following main sections:
• Prime mover: A squirrel cage three-phase asynchronous machine controlled by an inverter in four quadrant operation providing the mechanical power and torque necessary for the characterization of the machine under study.
• Data acquisition software for electric machines: performs the test automation and provides the user interface to execute the experiments.
The SW developed in LabVIEW communicates with the acquisition devices via serial port using the Modbus protocol, reading electrical and mechanical data from instruments.
• HMI gateway: provides the commands to the prime mover, so it can be used as drive, load or a speed and torque control to put the machine under test in a specific working condition or to simulate different load profiles such as fan, lift, etc.
• Instruments: collect mechanical (speed, torque and temperature) as well as electrical data (AC and DC, Voltage, current and Power).
The didactic acquisition and automation software guides the student through the different experiments available for the study of various types of single and three-phase AC, DC and brushless machines, motors and generators, through an intuitive user interface.
The automated test approach enables the student to monitor and control several variables of the electric machine under test in real-time, to easily observe their behaviour and interaction under several operating conditions such as load, no load, variable speed and torque, or different excitation
values. The characteristic curves that can be obtained with the system provide accurate information to create a model of the machine, tune its controller and study the machine applications.
According to the machine under test, the studies that can be performed include:
• Motor and generator operation
• Torque vs. speed characteristic
• Torque vs. current characteristic
• Voltage vs. speed characteristic
• Generator synchronization with network
• Power factor.