Air-gap Effect on Single Axis Vibration Analysis of Electromagnetic Braking Using Eddy Current on Bearing Cage M.Z.Baharom 1,a , M.Z.Nuawi 1,b , M.S.Salleh 1,c , G.Priyandoko 1,d , C.K.E.Nizwan 1,e 1 Advanced Structural Integrity and Vibration Research Group (ASIVR) Faculty of Mechanical Engineering, Universiti Malaysia Pahang, 26600 Pekan, Pahang, Malaysia. 2 Department of Mechanic and Material Engineering, Faculty of Engineering and Build Environment, Universiti Kebangsaan Malaysia, 43100 UKM Bangi, Selangor, Malaysia. a zairi@eng.ukm.my, b zaki@eng.ukm.my, c msazali@ump.edu.my, d gigih@ump.edu.my, e eddy@ump.edu.my Keywords: Electromagnetic braking vibration, eddy current, air-gap, Dasylab. Abstract. An electromagnetic braking system using eddy current experiment was conducted to study the behaviour of the system in terms of vibration. Brake disc use which is Al6061 has a displacement in z-axis direction which occurred because of the repulsive force generated on both sides of the disc as drag force from electromagnetic braking. This study aims to analyze the vibration behaviour when braking occurred in different initial speed of DC motor and different air- gap case. Smaller air-gap will produce high braking torque due to the increasing of magnetic field density. The higher the force generated, the vibration of the disc may illustrates different behaviour of the vibration in the structure. Test rig developed using sensor of accelerometer and data acquisition of NI-DAQ with the use of Dasylab for the measurement and instrumentation purposes. Findings shows that the electromagnetic braking force generated in smaller air-gap between electromagnetic poles and rotating conductive disc during the braking using eddy current has damped the vibration occur in the structure of bearing cage. Introduction Movement of a conductor through a stationary magnetic field or a time varying magnetic field through a stationary conductor will generates electromotive forces. Eddy current generated when a non-magnetic conductive metal is placed in a magnetic field. These eddy currents circulate in such a way that they induce their own magnetic field in opposite direction of the applied force. This situation will cause a resistive force [1]. Electromagnetic braking using eddy current is not limited to be used as an alternative braking system only. In the field of dynamic system, the continuous movement of the conductive metal in the magnetic field region will produce changes in magnetic flux [2]. This will induce electromotive forces which will allow the currents induced to produce repulsive force [3-5]. The force produced is proportional to the velocity of the conductive metal which in this case is the disc brake. In this study, the use of eddy currents had been explored as a damper for the dynamic systems. Eddy currents will act like a viscous damper and control the vibration of the structure which is bearing case. Therefore, aims of this study to see the vibration behaviour when the electromagnetic braking takes place. Rotating element which is the aluminium disc brake used in this study is connected to a frame which accelerometer been placed. The vibration measured in single axis which is parallel to the repulsive force direction.