METHOD AND SYSTEM FOR REDUCING ELECTROMAGNETIC INTERFERENCE IN A REFRIGERATION SYSTEM

摘要

The present invention relates to a technique for reducing the levels of electromagnetic interference in refrigeration systems equipped with frequency inverter. The technique, known as Jittering, consists of cyclically varying the switching frequency of the bridge inverter. One of the ways in which the present invention may be embodied is by a method of reducing electromagnetic interference in a refrigeration system, said system comprising a variable speed electric motor (10) controlled by a bridge inverter (15) activated by a PWM modulation signal, said PWM modulation having a modulation period (T_PWM) which varies between a maximum modulation period (T_PWM-MAX) and a minimum modulation period (T_PWM-MIN), said method comprising a step of continuously varying the modulation period (T_PWM) between the maximum modulation period (T_PWM-MAX) and the minimum modulation period (T_PWM-MIN), SO as to gradually increase and decrease the period (T_PWM) between the maximum and minimum values in each new PWM modulation period to attenuate the amplitude of the PWM signal at its fundamental frequency and its harmonic frequencies.