Experimental study of electromagnetic disturbances generated by variable speed drives for direct link DC motor

Abstract

Electromagnetic interferences (EMI) are generally recognized as the main reason for failure in digital circuits. They cause problems of interactions between parasites all control components and the variable speed drives control structure. In particular, for power inverters, one of the most common problem in the optimal definition is the analysis of electromagnetic interferences, which usually works digitally. In this paper, the analysis shows that electromagnetic interferences depend mainly on individual configurations circuit control board and also the absolute level of emission control devices which reaches a maximum value around some particular frequencies. It's possible to work on the level which ensures maximum transmission control signal error under a certain value. Therefore, the variator can be designed to operate at a frequency which doesn't generate major disruptions, hence there will be no need for solution to decrease the distance between the control circuit, power supply and the load. The objective is to establish the permissible disturbance level for the speed controller circuit. These operations of major default, when the electromagnetic disturbances generally coming from the control part of the speed variator have an amplitude which give rise to undesirable changes in the state of the logic signals. By way of example, a DC speed variator based on the MOSFET power transistor assembled with a DC motor constitutes the assembly which is tested in this work. Some detailed results of the electromagnetic disturbance analysis are presented in this article.