In order to meet the European directive 89/336/EEC Electro-Magnetic Compatibility (EMC)
The equipment manufacture, systems integrator and installer shall comply with the requirements of the directive.
Electrical & Electronic equipment shall be constructed such that:-
Compliant equipment shall carry the CE mark.
Electromagnetic interference problems associated with VSD’s:-
Need to consider the mains interference and harmonic distortion. Harmonics are a sinusoidal component of the mains fundamental frequency (50 Hz). Harmonics are generated by equipment such as, power electronics, drives, transformers and arc welders.
Distortion caused be harmonics on the mains supply effects the correct operation of other equipment on the supply system. (Overheating problems, causing failure).
Therefore this is an important issue for the electricity authorities. Hence legislation, level. Requiring the reduction of harmonics level.
The high frequency voltage rises (dv/dt) travels along the cable to the motor, stresses the motor insulation causing insulation deterioration and premature ageing.
Earth and Shield (screen) cables have to be installed according to the instruction manual and the relevant EMC guidelines. Correct screening and earthing is very important in reducing the effects of interference to other equipment and also correct and safe installation of VSD & filters.
1) EMI. Causes distortion of the mains 50 hz waveform.
2) RFI. High frequency signal superimposed on mains 50 hz waveform. Generated by communication equipment and high frequency electronic equipment.
Up to 10 Mhz is usually conducted.
Above 30 Mhz is radiated.
3) Filter leakage current must be taken into account in terms of safety and its effect on RCD devices.
Attenuation up to 30 Mhz.