Page 158 - Industrial Power Engineering and Applications Handbook

6/138 Industrial Power Engineering and Applications Handbook
Pump head

0 4 4
Capacity 'Q'-
(a) Discharge versus suction head

Capacity 'Q' -
0 4 4 Q,

(b) Discharge versus pump power

Figure 6.41 Power saving with the use of static control compared to throttle control

Considering the efficiency of slip recovery system as 95% 6.16 Application of static drives
and 300 operating days in a year, the power feedback to the
main supply source through the slip recovery system in 20%
of the time, 6.16.1 Soft starting (Vlf control)
= [0.95 x 791 . [0.2 x 300 x 241 This facilitates a stepless reduced voltage start and smooth
= 108 072 kWh acceleration through control of the stator voltage. The
smooth voltage control limits the starting torque (T,J
And in terms of costs at a tariff rate of Rs 1.2 per unit, and also the starting inrush current (IJ a5 illustrated in
= RS 1.2 x 108 072 Figure 6.43. This is achieved by arranging a full-wave
phase-controlled circuit by connecting two SCRs in anti-
= Rs 129 686.4 per year parallel or a triac in each phase as illustrated in Figure