Design Guideline of Contactors: Optimal Use of Assembled Contacts

Real performance of a large number of 18.5kW contactors available on the market are presented with their evolution over the last 10 years. Significant disparities were observed. They are mostly independent of electrical contacts implemented. By contrast, a strong presumption is issued on the dependence of the contact force which becomes weaker and weaker. In preamble, the evolution on test machine of an electrical contact during all its service life is presented. This study highlights the potential of AgSnO2 optimally used. A reasonable increase of the contact force of a real contactor is then performed in order to study the real impact of this parameter. The contactor chosen provides AC3 performances in the general average and one of the weakest contact forces. Contacts remain strictly unchanged. Results obtained in temperature rise and AC3 endurance are presented and a first explanation of the gains obtained is given. A further improvement is proposed. It should allow getting the best possible rate of use of contacts implemented. To conclude, recommendations are made to allow a maximum reduction of current and future costs of the contactors.