Development of testing apparatus for investigating electromagnetic dynamics of contactors: A pilot study

It is easy to find electromagnetic contactors in modern electromechanical devices owing to their advantages, which encompass a simple structure, ease of use, and low cost. However, these devices also have inherent drawbacks, including heat dissipation, contact erosion, and inefficient power consumption during long-term operation. This has sparked interest in contact soft-landing, which aims to reduce issues like contact bounces, contact welding, and arcing. This paper presents the development of a testing apparatus for investigating the electromagnetic dynamics of contactors or mechanical relays, aimed at developing an open-loop model-based controller for contact soft-landing. Theoretical equations based on physical theorems are derived to describe the behavior of the electromagnetic coil under varying factors. Additionally, a pilot study was conducted using the proposed testing apparatus to explore the relationship between heat dissipation, flowing current, air gap, and the Lorentz force produced by exposing ferromagnetic material to the magnetic field surrounding the electromagnetic coil. The experimental and simulation results showed good fitting, with a normalized root mean squared error ranging from 2.5% to 4.5% for various scenarios. Notably, it was found that the flowing current passing through the electromagnetic coil can be controlled by changing the duty cycle of the pulse width modulation signal driving the conductivity of the MOSFET. However, the results suggest that a modulation frequency greater than 5 kHz is not suitable for driving the electromagnetic coil.