i have YORK centrifugal water cooled chillers, Model# YK FD FD H45 CNE0,00 with Harmonic Filter and is VSD, Capacity 500TR each, Manufactured by York Europe. According to the manual the system is designed 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 inturn causes tripping off chillers. the problem is very serious. i want to change the design parameters of Harmonic Filetr Input Frequency range of the York Chillers. i want new range in between 47-51 Hz so as to avoid the shut down of chillers. Someone can help me in doing so and can guide me in this matter? Also plz cooperate me and tell me what will be the effects of new Range (47-51Hz) of Harmonic Input Frequency on other operational segments of chiller like VSD, ISN etc.