Rectangular closed double magnetic circuit for vibration exciter with 1.2m stroke

High performance magnetic circuit offering long stroke is the key of developing a vibration exciter for ultra-low-frequency (ULF) vibration calibration. A rectangular closed double magnetic circuit (RCDMC) offering ultra-long stroke up to 1.2 m is proposed. The method of fabrication and assembly of NdFeB magnets with a dimension of 420 mm x150 mm x 50 mm is discussed and force simulation analysis is carried out. The maximum assembly force is less than 3kN with radial assembly method. A RCDMC prototype has been successfully developed and applied in a horizontal ULF vibration exciter Experiments are carried out with a RCDMC prototype developed for a horizontal vibration exciter. Experimental results show that a MFD of 102 mT and non-uniformity of MFD of 0.2% along 1.4 m air gap are realized, making the proposed RCDMC a solution for ULF vibration calibration.