A Holographic Measurement of Microscopical Sliding of Electrical Contact Due to Contact Spring Thermal Deformation

A deflection of a contact spring occurs with environmental temperature change or Joule's heat due to current flow, which causes a microscopical slide of the contact point and sometimes so-called fretting corrosion. In order to analyze the microscopic deformation due to thermal stress, it is essential to develop a measuring method of such a fine contact point displacement. The authors have developed a holographic pattern measuring system (HPMS) which combines both techniques of holography and graphic image processing, and the HPMS was applied to the thermal deformation of a contact spring. As a result, the microscopic displacement of the contact spring could be quantitatively measured in a noncontact way, and the distribution of the displacement could be shown automatically as a three-dimensional graphic image. From the above results, when thermally excited by the current flow through electric contact, the quantitative correlation between the slide of contact point and the thermal deformation of contact spring was obtained. In addition, the authors found some irregularity in contact voltage in case of the current flowed through the closing contacts. From the deformation analysis of the contact spring, the relationship between the contact voltage and the deformation of the contact spring due to current flow was made clear.