The Electroil inverters have a switching frequency of the IGBT on the power terminals variable between 5 and 7.5 kHz depending on the models. This relatively high frequency, compared to 50 Hz of the power line, in presence of connection cables between inverter and motor longer than 20 meters, can determinate the arising of leakage capacity currents towards ground on the motor connection cable. These leakage currents may cause high impulsive over-voltages on the motor, with a peak value sometime higher than 1000V which may limit the life of the insulations of the motors itself, if such a materials are not of adequate quality.
For the operation with inverter and motors connected with long cables, independently from the utilisation or not utilisation of the output filter, we always suggest to use pumps with motors with good quality insulations and in particular it’s goods that there are :
phase-separators on the head of the stator, in order to avoid that the insulating enamels, stressed by high peak voltages, can deteriorate as time passes;
insulated bearings (ceramic) in order to avoid the closing of high frequency leakage currents, on the armature shaft, which may damage the balls.
The sinusoidal output filters we offer are highly recommended in case the motor-pump does not comply with one or more of the conditions indicated as above and the motor cable is longer than 20 meters.
Therefore, the sinusoidal output filters are extremely useful for the EMC noise suppression that could affect electronic systems very susceptibles like, for example, video-cameras, alarms, or audio/video data transmission signals, in case the data networks of these devices are installed on the same pipelines of the inverter-motor supply cables, also if shielded (system solution strongly discouraged).
Our output filters are of high quality (always produced in Italy or in Germany), with low heating and low voltage drop, for supplying of single phase or three-phase motor-pumps; they are LC types filters (inductive and capacitive) in order to make the most possible sinusoidal, and free of peaks, the voltage waveform that arrives to the motor; they can be delivered in the standard version, at sight, or encased in a metallic box IP54.
For the efficiency of the filter, it must be placed as close as possible to the metallic case of the inverter, downstream of the same inverter, at the beginning of the motor supply cable.
All output filters offered by Electroil have been tested combined with Electroil inverters, and if used combined with the EMC filters connected on the input, in presence of long motor cables, besides limiting the overvoltages on the motor, such a filters also help by increasing the efficacy of the interferences suppression.