Abstract
Starting methods for ac motors range across a broad spectrum from across-the-line starting to various types of reduced voltage starters; more recently, electronically controlled starting is being used. When rated voltage is applied to a motor at standstill, the inrush current is several times the rated load current. For motors in the medium ac size, the starting torque accompanying this high inrush current generally exceeds 100% of full-load torque, and for smaller horsepower sizes, starting torques of 200% or more are common. For most applications, these starting torques are adequate to start the load and, if the power system supplying the motor is not adversely affected by the inrush current, across-the-line starting can be used. However, if the power supply suffers a severe voltage dip when required to supply the motor’s inrush current, then an alternate type of motor starting control may be needed. Light flicker is a common symptom of voltage reductions that occur during motor starting. This is often tolerable, but if the voltage reduces to such a low level that the motor will not start the load, then some corrective action needs to be taken. Computers and production equipment may also be susceptible to voltage dips and may malfunction. If any of these problems create unacceptable conditions, then reduced voltage starting is indicated.
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References
NEMA Standards Publication No. ICS2, “Industrial Control Devices, Controllers and Assemblies.” Washington, D.C.: National Electrical Manufacturers Association, 1988.
Courtin, J.J. Ten part-winding arrangements in sample 4-pole induction Motor, IEEE Transactions, Part III, Power Apparatus and Systems, Vol. 74, 1955.
Veinott, C.G. Theory and Design of Small Induction Motors. New York: McGraw-Hill Book Co., 1959.
Veinott, C.G., and Schaefer, L.C. Fundamental theory of inherent overheating protection under running overload conditions, AIEE Transactions, Power Apparatus and Systems, 1949.
National Electrical Code, National Fire Protection Association, Boston, 1981.
“Guide for Construction and Interpretation of Thermal Limit Curves for Squirrel-Cage Motors Over 500 Horsepower,” P620, IEEE, New York, 1981.
NEMA Standards Publication No. MG1, “Motors and Generators,” Washington, D.C.: National Electrical Manufacturers Association, 1993.
Koerber, A.R. Surge protection for rotating electrical equipment, Plant Engineering, Sept. 7, 1972.
Shankle, D.F., Moses, G.L., and Mole, C.J. Steep-front surges endanger windings of powerhouse motors, Electric Light and Power, November, 1966.
Andrä, Walter and Sperling, Paul-Gerhard. “Winding Insulation Stressing During Switching of Electrical Machines,” Siemens Review, XLIII, No. 8, 1976.
Walsh, G.W. A review of lightning protection and grounding practices, IEEE Transactions on Industry Applications, Vol. IA-9, No. 2, March/April, 1973.
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© 1994 Springer Science+Business Media New York
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Jordan, H.E. (1994). ac Motor Control and Protection: Starting, Running Protection, and Surge Protection. In: Energy-Efficient Electric Motors and their Applications. Springer, Boston, MA. https://doi.org/10.1007/978-1-4899-1465-1_8
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DOI: https://doi.org/10.1007/978-1-4899-1465-1_8
Publisher Name: Springer, Boston, MA
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