Design and Optimization of Helmholtz Coils For Magnetic Fields

The objective of this work is to investigate the axial magnetic fields and radial magnetic fields of Helmholtz coils under copper chromium electrodes by using a pulse current generator. The vacuum circuit breaker electrode is the heart of its longevity. Based on the simulation results, COMSOL software was used to model the Helmholtz coils. It observed that the coils generate strong magnetic fields between copper and chromium electrodes. The novel Helmholtz coils have been tested through high voltage switching capacitor banks up to 2 kV. In the experiments, a pulse capacitor bank was used to generate arc voltage up to 50 kV. Furthermore, the generated arc voltage using Helmholtz coils was capable to propagate magnetic fields up to 55 mT. The Helmholtz coils influence on the arcs while producing magnetic fields were observed by a high-speed camera. Two types of magnetic fields were measured at different points using a Hall effect sensor. By using this switching technique, the Helmholtz coils increased the breaking capacity of the vacuum circuit breaker at high-speed velocities.

I. Introduction

Copper chromium electrodes are frequently used in vacuum interrupters due to their mechanical, electrical and thermal properties. The nanomaterials are boomed in 21st century due to their unique application. It is extremely difficult to manufacture these materials, which are made by different methods. Due to economic reasons, electric power systems must operate with an efficient power factor. Pulse capacitor banks are widely used in electric power systems to maintain the power factor. A typical energy management system regulates power by switching pulse capacitor bank [1]. The small size, long mechanical life, maintenance-free nature, and environmental friendliness of vacuum circuit breakers (VCBs) make them one of the most widely used electrical components [2]. When switching pulse capacitor banks, VCBs behave according to inrush current, not interrupted operations. When contacts are welded together during the previous capacitive-making process, a protrusion will form on the contact surface of the VCB. A vacuum circuit breaker is frequently used on the output side of pulse capacitor banks to operate them in this way. In power systems with middle voltages, vacuum interrupters are widely utilized because they require no maintenance and are environmentally friendly [3]. High voltage vacuum interrupters have been developed based on short circuit resistance and current carrying capacities [4]. Vacuum arc control and loop resistance are directly affected by electrode contact design, which primarily determines how much current can be carried over a short time period. Magnetic fields generated by electrodes can be significantly influenced by electrode design in order to achieve better vacuum arcs. In vacuum arc circuit breaking facilities, transverse magnetic fields (TMFs) and axial magnetic fields (AMFs) were the most investigated types of magnetic fields. There were first proposals for TMF contacts in the 1960 [5]. The vacuum arcs on the contact surface rotate in a perpendicular magnetic field generated by this kind of contact. Low resistance is a common characteristic of TMF contacts, which allows the rated current to be increased.