MODELING A PERMANENT-MAGNET DC MOTOR CENTRIFUGAL PUMP ASSEMBLY IN A PHOTOVOLTAIC ENERGY SYSTEM

Direct current (DC) motors and centrifugal pumps operate at variable s peed in a photovoltaic pumping system. However, the characteristics of motors and pumps are usually only given for a single voltage and spee d. To analyse the diurnal operation of a pumping system, where the sol ar radiation varies causing Variation in the photovoltaic power, the i nput/output relationship of the motor-pump assembly must be determined . In this article we show that pump similarity laws may be applied to the analysis of centrifugal pump performance for variable speed operat ion. Modelling equations of the motor-pump assembly are derived from s ingle speed pump characteristics and a no-load motor test. The applica tion of the modelling equations in conjunction with the equation chara cterising the photovoltaic array yields the relationship between solar radiation and pump flow rate for a given pipeline. (C) 1997 Elsevier Science Ltd.