Some Observations on Multiplicity and Operating/Processing Modes of PC Loads with UPS

Presently computer loads and systems are extensively used almost in every field of daily life, where computers have to play very important and decisive role like healthcare, banking, safety systems etc. These critical facilities rely on uninterruptible power supply (UPS) to maintain a continuous supply of power, during power failure and to provide reliable service. The UPS supplies the mean power to PC load connected to it, but this combination of LIPS and PC load works as a harmonic source. This paper reports some experimental measurement results about harmonic currents generated by single and multiple personal computer (PC) loads connected with UPS, as in most practical conditions the UPS is found connected to PC load. Furthermore, to investigate the impact of UPS connected with PC load, a comparative study is also presented, where measurements are taken under two different conditions, i.e. PC load without UPS and with UPS. Two processing modes are investigated, i.e. idle mode, and hard disc drive (HDD) processing mode. The measurements taken for these two processing modes are combined with two different conditions of monitor status: with monitor power ON and with monitor power OFF. Parameters considered for investigation are mis load current, its harmonic distortion, power consumption and harmonic spectrum of load current. Attenuation of harmonic components due to multiplicity of PC load is also studied.