Gear up your bearings

This article identified three electrical mechanisms that cause bearing damage. The three sources of bearing currents are electromagnetic induction (circulating current), electrostatic EDM coupled sources (mechanical or electrical coupled), and ground sources (backfeeding). This also presented field test measurements related to bearing damage. A field methodology was presented to identify electrical bearing conditions in motors that are still running. Mitigation actions are described and applied to two motor ASD application sites. Test measurements were taken to determine the effectiveness of the mitigation action. In most cases, two or all of the bearing current mechanisms can be identified by reviewing the installation and application of the motor with voltage and current measurements with time and frequency analysis. A combination of mitigation strategies is normally used on the basis of the bearing current coupling mechanisms.

[1]  John Boyd,et al.  The Conduction of Current in Bearings , 1959 .

[2]  Doyle F. Busse,et al.  The effects of PWM voltage source inverters on the mechanical performance of rolling bearings , 1996, Proceedings of Applied Power Electronics Conference. APEC '96.

[3]  Doyle F. Busse,et al.  Characteristics of shaft voltage and bearing currents , 1997 .

[4]  I. Kerszenbaum.  Shaft currents in electric machines fed by solid-state drives , 1992, 1992 IEEE Conference Record of the Industrial and Commercial Power Systems Technical Conference.

[5]  M.J. Melfi,et al.  Bearing current remediation options , 2004, IEEE Industry Applications Magazine.

[6]  H. E. Boyanton,et al.  Bearing fluting [motors] , 2002 .

[7]  P. J. Link,et al.  Minimizing electric bearing currents in ASD systems , 1999 .

[8]  Doyle F. Busse,et al.  An evaluation of the electrostatic shielded induction motor: a solution for rotor shaft voltage buildup and bearing current , 1996, IAS '96. Conference Record of the 1996 IEEE Industry Applications Conference Thirty-First IAS Annual Meeting.

[9]  Har Prashad.  Solving tribology problems in rotating machines , 2006 .

[10]  Hamid A. Toliyat,et al.  Handbook of Electric Motors , 2004 .

[11]  S. W. SAYLORS.  Motor bearing failure from VFD induced shaft to ground voltages in HVAC applications , 1995, IEEE Technical Applications Conference and Workshops. Northcon/95. Conference Record.

[12]  K. Reichert,et al.  Shaft voltages in generators with static excitation systems-problems and solution , 1988 .

[13]  D. W. Schlegel,et al.  Experience with variable frequency drives and motor bearing reliability , 1998, Record of Conference Papers. IEEE Industry Applications Society 45th Annual Petroleum and Chemical Industry Conference (Cat. No.98CH36234).

[14]  M. J. Costello,et al.  Shaft voltages and rotating machinery , 1991, Industry Applications Society 38th Annual Petroleum and Chemical Industry Conference.

[15]  Doyle F. Busse,et al.  System electrical parameters and their effects on bearing currents , 1996, Proceedings of Applied Power Electronics Conference. APEC '96.

[16]  Har Prashad.  Theoretical Analysis of Capacitive Effect of Roller Bearings on Repeated Starts and Stops of a Machine Operating Under the Influence of Shaft Voltages , 1992 .

[17]  J.A. Lawson.  Motor bearing fluting , 1993, Conference Record of 1993 Annual Pulp and Paper Industry Technical Conference.

[18]  A. Muetze,et al.  Don't lose your bearings , 2006, IEEE Industry Applications Magazine.

[19]  P. L. Alger,et al.  Shaft currents in electric machines , 1923, Journal of the American Institute of Electrical Engineers.

[20]  Doyle F. Busse,et al.  Bearing currents and their relationship to PWM drives , 1997 .

[21]  Thomas A. Lipo,et al.  Circulating type motor bearing current in inverter drives , 1998 .

[22]  J. Erdman,et al.  Effect of PWM inverters on AC motor bearing currents and shaft voltages , 1995, Proceedings of 1995 IEEE Applied Power Electronics Conference and Exposition - APEC'95.

[23]  Thomas A. Lipo,et al.  Bearing currents and shaft voltages of an induction motor under hard and soft switching inverter excitation , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.