i have YORK centrifugal water cooled chillers, Model# YK FD FD H45 CNE0,00 with Harmonic Filter and VSD, Capacity 500TR each, 400volt.3phase.50Hz, Manufactured by York Europe. According to the manual the system is warned for Harmonic Filter input frequency 49-51 Hz (on 50Hz power supply line). Unfortunately i am facing frequency fluctuation problem most of the time between 47-48.8Hz in the commercial power supply line which results is shutdown of chiller. The shutdown alarm is shown on the Chiller display as " 110% harmonic filter input current overload. When I look into the history detail of this alarm, the rms current derived by all the three phases of Harmonic Filter is within the acceptable limit. The problem is very critical. i want to know the root cause of this problem. i also want to have my York chillers run troublefree in between input frequency range 47-51 Hz. Also anyone who has the solution of this problem can guide me thoroughly as soon as possible.