B. Some Important relationship derived
Parameters of Motor Used: 0.5 H.P., 230V DC, 1.5A,
3000rpm
Magnetization characteristics of a DC motor is always non-linear hence the relation of Eb( back emf) and speed is derived
by fitting the experimental data of magnetisation curve. The
following relation is used for determining the back emf for any
given speed or vice-versa for any given value of field current.
Eb=N*(273.4*(If^3)-(582.5*If^2)+(609.5*If)+18.47)/1500..............(1)
Relationship between Pinput and speed of pump- motor set
is obtained by fitting the experimental data of a DC motor
driven centrifugal pump to a curve. The following relation is
used for determining the mechanical power required to drive
the pump- motor set at any given value of speed (N) or vice-versa.
Pinput=-(1.01*10^(-8)*N^4)+(4.242*10^(-5)*N^3)-(.06455*N^2)+(42.86*N)-(1.009*10^4).................(2)
I/V characteristics of PV array (where all the symbols used
carry their usual meaning)
Ipv=Iph-(Ir*(exp((Vpv+Ipv*Rse)/Vt)-1))-((Vpv+Ipv)*Rse)/Rsh)...........(3)
Utilization factor of Solar array is given by:
U.F.= (Load power absorbed/MaximumPower available at
array)…..(4)
Field Current in differential compound motor
If= Iffixed- dc*(Ia); where dc is degree of
compounding……(5)
Relationship between speed of motor-pump set and Q
(discharge rate in lit per litres/sec.) is obtained by fitting the
experimental data of a variable speed DC motor driven
centrifugal pump , to a curve.
Q=-(1.914*10^(-7)*N^2)+(0.0004492*N)-0.07947………..(6)
C. Proposed Schemes for Maximizing Water Output.
For maximizing the water output speed of the DC motor is
to be maximized. To maximize the speed following three
schemes are proposed so that the utilization factor of solar array
can be maximized over the day and maximum water can be
collected over the day.