Research on Assessment Method of Pick-up Voltage Qualification Rate for Batch Balanced Force Relays Considering Permanent Magnet Degradation

The permanent magnet(PM) is the core component of the electromagnetic system in a balanced force electromagnetic relay. Its magnetic property degrade over time, thereby affecting the performance of relay and even the qualification rate of batch relays. Therefore, this article investigates the impact of PM degradation on electromagnetic force based on degradation model, and obtains the changes in pick-up voltage. Furthermore, predicts the qualification rate of batch relays after a certain period of time. Firstly, a simulation model for static electromagnetic attractive force is established based on the Preisach model and the finite element method. Based on the established model, a single factor analysis was conducted on each parameter to determine the key parameters that significantly affect electromagnetic attractive force and pick-up voltage in electromagnetic system. Using the Kriging model, a fast calculation method for electromagnetic torque is established with the selected key parameters as inputs. Then, accelerated degradation test of PM is conducted and surface magnetic strength data is collected to establish a index degradation model about time and temperature. Generate virtual samples of batch relays, use Kriging fast calculation model to obtain the distribution of initial electromagnetic attractive torque, and use theoretical calculation to obtain the distribution of initial mechanical counter torque. Randomly match the attractive torque and counter torque when the coil voltage is the lower limit of pick-up voltage, and obtain the assessment result of qualification rate of pick-up voltage after 10 years of PM degradation.