2S12: Understanding the Twice-Line-Frequency vibration

Jason Tranter, Founder and CEO, Mobius Institute


Have you ever wondered why there is a peak at twice line frequency? Have you wondered why that vibration changes in amplitude? This presentation will answer all of those questions and also help you to understand how induction motors work and why we see some other faults in induction motors. Using lthe Mobius simulations and animations, Jason will provide an explanation for how electric motors are powered (even from VFD’s) and why that creates a magnetic force at twice the line frequency (e.g. 100 Hz or 120 Hz in United States and a few other places). Even if you are mechanically oriented and have never considered the electrical side of an induction motor, this presentation will be perfect; finally revealing what is happening inside the motor and why the vibration changes, particularly at twice line frequency.


Jason Tranter (BE Hons) has been involved with condition monitoring and vibration analysis since 1984. In 1986 Jason formed his Australian company, ARGO, which was heavily involved in vibration monitoring and systems development. In 1990 he sold that company and the “ALERT” product line to DLI Engineering in Seattle (now AzimaDLI). Jason was in charge of product development, and later in charge of vibration products. In 1996 Jason returned to Australia and for the next three years he developed the ExpertALERT (EAV), DCX data collector, and DCX Online products for DLI Engineering. In 1999 Jason formed Mobius and began the development of the iLearnInteractive series of computer-based products for vibration and alignment training and analysis, including iLearnVibration, iLearnAlignment and Interpreter. These products have been used by thousands of people in over 90 countries to learn and become certified. Mobius was awarded the Victorian Regional Exporter of the year and was a finalist in the Australian Export Awards for 2007 and 2008. In 2005 Jason formed the “Mobius Institute” for expanded distance learning and public courses, and courses that comply with ISO and ASNT standards for certification. Mobius has offices in Australia, the United States and Costa Rica, and training centers in over 40 countries. In 2010 Jason formed the Mobius Institute Board of Certification, a not-for-profit organization to make it possible for vibration analysts anywhere in the world to achieve certification per ISO 18436-1. Jason has delivered technical papers around the world, and has had articles published in numerous international magazines and journals.