Laboratory investigation of the input current characteristics of modern domestic appliances for varying supply voltage conditions

The past decade has seen major changes to the appliances which comprise the domestic load. Appliances which may have been considered to be passive loads are now supplied through power electronic front ends. These new loads are known sources of power quality disturbances, predominately harmonic currents. While examinations have been made of the electrical behaviour of first generation electronic appliances, there is little literature dealing with the performance of more modern loads. Understanding the behaviour of modern loads is essential if accurate models of equipment connected to the power system are to be developed. This paper examines the input current characteristics of a number of modern domestic appliances. This includes an analysis under undistorted rated voltage input conditions along with examination of the impact that varying input voltage conditions has on appliance input currents. Characterisation of the appliance input current is achieved through a laboratory testing regime using a programmable power source. On the whole, it can be noted that many modern appliances have input current performance which is better in terms of harmonic content compared to older appliances with power electronic front ends. With respect to variation of the input voltage, it has been found that harmonic distortion has a larger impact on the input current of appliances than variations in fundamental voltage magnitude.