2.2 Motor model
Since the output produced by PV generators is DC power, a
DC motor is usually employed instead of AC motors in the
PV pumping systems, because DC motors can be more easily
interfaced with PV generators without using DC to AC power
conversion. Therefore, the overall system cost and complexity
will significantly reduce. In this work, a permanent magnet
DC motor is used to drive a centrifugal pump load. The
permanent magnet DC motor has some advantages such as
reliability, high efficiency and relatively infrequent
maintenance [8]. Moreover, the PMDC motor coupled with
centrifugal pump has suitable matching characteristics with
the PV array characteristics and its starting low torque is low
compared to other PV electro-mechanical systems [8] and [9].
Figure (2) illustrates the equivalent circuit of the permanent
magnet DC motor with the pump load.