Design och framtagande av mätanordning för ström och effek på trefas ledare
Josi Periferi strömmeter
EffektmätningTrefasledareFörstärkarkretsAsymmetriskt magnetfältMatlabNational InstrumentDaq usb-6211Standalone.
The assignment is issued by Scania Maintence AB seeking a new approach to detect power changes in their industrial processes. The work has taken place at Ångströmslaboratoriet and tests have been performed at Scania AB Södertälje.Today?s society consumes enormous amount of energy. In both economically and environmental view, it is important that the processes are effective, with high power factor. There are many ways to measure power in the industry, what they all have in common is that the installation is advanced, requires time and planning. Only a competent electrician may install the measuring device in the distribution box. The purpose of the project is to build a prototype for power measurement that can be easily used outside the distribution box, thus simplifying the procedure and shortening the time required. By attaching sensors around the supply cable, the magnetic field asymmetric flux density can be used and induce voltage proportional to the current in the cable.The result is an instrument that with a computer calculates current, phase angle and power. Measurements of the current rms value showed that the maximum difference between our prototype and Scania Maintenances equipmentis up to 29 percent. However, for a longer time (> 15 minutes) the differences between the mean values are only 1.2 percent and the accuracy is calculated to +/-3.67A with 95% confidence intervals. Phase angle accuracy measured to plus 6 minus and 15 percent.