The variable speed adjustment for feed water pumps has well energy saving performance.However

whether the feed water pump can keep running with a high efficiency under variable load conditions has not been researched yet.Thus

suggestion that applying the cooperative regulation in large and medium-sized units under variable load conditions and with main steam turbine in sliding pressure operation and the boiler main feed water pump employing variable speed regulation was proposed.By taking a single set of tandem pumps in feed water system of a 200MW unit boiler as the example

calculation on this scheme was conducted.The results show that

when the cooperative regulation is put into service

the main feed water pump keeps running with the maximum efficiency

which is higher than both the feed water pump efficiency and booster pump efficiency when only the variable speed regulation is applied;the total power consumption of the pumps is lower than that when only the variable speed regulation is applied.Moreover

with a decrease in unit load

the energy saving ratio increases remarkable.It reaches about 58% when the unit load drops to 50%.