A comparison between DC and AC drives as regards their behaviour in the presence of voltage dips: new techniques for reducing the susceptibility of AC drives

Electrical adjustable speed drives are sensitive to voltage interruptions. The occurrence of voltage dips in the power supply to pieces of equipment may cause them to stall, and cause production losses. Here, an examination is made of the behaviour in the presence of voltage dips in supplies for thyristor controlled DC drives, and of different kinds of AC drives. A discussion on AC equipment sensitivity attenuating techniques, and on the options which manufacturers incorporate into their equipment in order to minimize that sensitivity is presented. A a description of the strategy used at the MEP (Spain) for the purpose of examining the cases brought in by customers whose equipment is affected by the voltage dips is also detailed. There are details on two cases that were examined, plus the suggested proposals for their solution. The paper is based on studies that have been conducted by MEP in conjunction with IBERDROLA, as were developed under the Electro-Technical Research Plan financed by Spain´s electric power utilities, with coordination by the Electro-Technical Research Coordination Office (OCIDE).