The high-voltage frequency converter has exellent regulating performance and obvious energy-saving effect.Along with decreasing its price and enhancing its quality

it has been adopted by more and more power plant to variable frequency retrofit for condensate pumps

but new problems after retrofit

such as the standby pump can't be started up under condition of losing power in operation mode of "one driving two"

and the water-level in deaerator lost control during the time of tripping the pump retrofitted to use variable frequency

and actuation of differential pressure protection for feed-water pump's sealing water under abnormal condition etc.

have occurred.For these

the problems occurred after retrofit have been analysed in detail

and corresponding solving measures being put forward.