Study on electrical discharge machining (EDM) in motor bearings
Lam, Jin Seng
Date of Issue2017-05-19
School of Electrical and Electronic Engineering
Rolls-Royce @ NTU Corporate lab
With the significantly improved characteristics and declining prices of power electronics equipment e.g., PWM variable frequency drive (VFD) have dramatically increased the use of electric propulsion in ships since the 1980s. Despite their excellent characteristics, PWM produce time-varying common-mode voltage (CMV), which, via different mechanism, can lead to motor bearing pitting, fluting, and premature failure. Consequently, new drive installations can fail within months resulting in unplanned and costly system downtime. This research was put to the test with high gain and switching frequency for industrial grade motor bearing. Providing an understanding to how bearing damage occur. More will be shown on the relationship between bearing discharge and external applied shaft voltage together with the dynamic impedance of the motor showing the different methods of measurement to be used. The project will focus more on Electrical Machining Discharge (EDM). Where a test rig is fitted with a VACON NXP series inverter is set up to provide a practical understanding towards what is the cause of bearing failure in modern AC drive system today. High gain and switching frequency will be subjected on the test rig with an external bearing set up to study the motor bearing under such conditions. The second portion will be used to understand the cable impedance using a bode100 measuring device.
Final Year Project (FYP)
Nanyang Technological University