The case for elimination of stray currents and magnetism in turbomachinery is being recognized as an issue to be dealt with in industries that design and operate rotating machinery. Of main concern are bearings, seals, gears, couplings, etc. Resulting problems extend from surface damage to unit crashes. It is important to recognize the symptoms, to heed the warnings, and to enact preventive and corrective measures. Recommendations are to eliminate or minimize the source, and to bond the machinery to ground, especially the shaft, with a reliable shaft brush and a qualified current monitor. Information and guidance are provided from MPS job files covering some of the 200 installations visited in the past 15 years.

Issue Section:
Technical Briefs
Topics:
Currents, Machinery, Magnetism, Bearings, Couplings, Damage, Design, Gears, Turbomachinery
1.
Alger
P. L.
, and
Samson
W.
,
1924
, “
Shaft Currents in Electric Machines
,”
AIEE Trans.
, Vol.
43
, pp.
235
–
245
.
2.
Ammann, C, Reichert, K., et al., “Shaft Voltages in Generators With Static Excitation Systems—Problems and Solutions,” Swiss Federal Institute of Technology, Zurich, Switzerland; Brown Boveri Company, Baden, Switzerland.
3.
Nippes, P. I., and Sohre, J. S., 1978, “Electromagnetic Shaft Currents and Demagnetization of Rotors of Turbines and Compressors,” presented at the 7th Turbomachinery Symposium, Texas A&M University, Houston, TX.
4.
Nippes, P. I., and Sohre, J. S., et al., 1981, “Panel on Electromagnetic Shaft Current Control,” presented at 10th Turbomachinery Symposium, Texas A&M University, Houston, TX.
5.
Nippes, P. I., 1992, “Detecting and Identifying Vibration Problems in Rotating Electrical Machinery,” presented at the 16th Annual Meeting of the Vibration Institute, Williamburg, VA.
6.
Rosenberg, L. T., 1955, “Eccentricity, Vibration, and Shaft Currents in Turbine Generators,” AIEE Transactions, Apr., pp. 38–41.
7.
Salomon, T., 1959, “Harmful Effects of Electrostatic Charges on Machinery and Lubricating Oils,” J. Inst. Pet., Vol. 45, Mar., No. 423.
8.
Schier, V., 1965, “Selbsterregte Unipolare Gleichstrome in Maschinenwallen,” Elektrotechnische Zeitschrift, Nov. 12 [in German], Translation #3925, “Self-Excited Homopolar Direct Currents in the Shafts of Machines,” Associated Electrical Industries, Ltd., Power Group, Research Laboratory, Trafford Park, Manchester 17, United Kingdom.
9.
Wilcock, D. F., 1949, “Bearing Wear Caused by Electric Current,” Electric Manufacturing, Feb., pp. 108, 111.
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 by The American Society of Mechanical Engineers
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