IEEE C37.18-1979 (R2003) pdf free.IEEE Standard Enclosed Field Disch arge Circuit Breakers for Rotating Electric Machinery.
IEEE C37.18 applies to all low-voltage power-circuit breakers that are intended for use in field circuits of apparatussuch as generators,motors,synchronous condensers,or exciters and embodying contacts for establishing fielddischarge circuits.
NOTE — In this standard, the use of the term “circuit breaker”shall be considered to mean “field discharge circuit breaker used
in enclosures for rotating electric machinery.”
In performing their function of interrupting field circuits of rotating electric machinery, field discharge circuit breakersare subject to the following conditions not met within the interruption of ordinary direct-current power circuits.
1) In alternating-current machine field circuits, in addition to the problems usually encountered in switching
highly inductive direct-current circuits, there is superimposed upon the voltage generated by the exciter, avoltage induced in the field windings by the transient current in the machine armature under alternating-currentshort-circuit conditions. These result in large pulsating currents in the field circuit as illustrated in Fig 1.2)Due to the large amount of magnetic energy stored in the machine field circuit, the interruption of the circuit
results in an unusually high transient voltage under alternating-current short-circuit conditions, unless specialmeans are provided for dissipating the energy.
3) A discharge resistor must be connected across the terminals of the machine field by the discharge contacts of
the circuit breaker just prior to disconnecting the field from its excitation source in order to provide fordissipation of the stored energy of the machine field and to minimize the transient voltage.The voltage acrossthe field discharge circuit breaker main contacts following interruption of the excitation source current isillustrated in Fig 2.
4) In addition to the above conditions, there is the usual direct-current short-circuit condition wherein the field
circuit may become short-circuited.
To cope with these unique conditions, this standard for field discharge breakers has been developed to establish therating structure and test requirements not encountered in other ANSI Standards which apply to other low-voltagecircuit breakers.
The dielectric test values given in Table 7A,ANSI C37.16-1979,Preferred Ratings, Related Requirements, andApplication Recommendations for Low-Voltage Power Circuit Breakers and AC Power Circuit Protectors, reflect thechange in dielectric test requirements in ANSI C50.13-1977 Requirements for Cylindrical Rotor SynchronousGenerators.IEEE C37.18 pdf download.
IEEE C37.18-1979 (R2003) pdf free
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