IEEE 421.1-2007 pdf download IEEE Standard Definitions for Excitation Systems for Synchronous Machines
3.8 automaticvoltageregulator(AVR: A term often used to desgnate either the voltage regulator alone or the complete control systemcomprised oflimiters, etc. See also: synchronous machine regulator. 3.9 autotracking:A function that causes the output ofa control channel in the standby mode to follow the acon ofan active contro channeforexample. autoacking ofthe mana control to flow the autcmatie control. Also called a follower.
3.10 suxiliary winding excitation system: An excitation system whose energy is derived from a separate dedicated pover winding in the main generaor’s stalor. NOTE-See Figure A.10.
3.11 brushless exciter: An alternator-rectifier exciter emploving rotating rectifiers with a direct connection tothe smchronous machine field. thus clminatng the need for brushes. NOTE-See Figure A.6.
3.12 bumpless trunsfer:A transter between two control modes that results in negligible change in synchronous machine output.See also: aull balance. 313ceilingcurrent:The maximum field current that the excitation system is desicned to supply. Typically.this is related to the themal capability of the excitation system equipment or the synchronous machne held crcunt capabubty.Seealso:overexcitation limiter.
3.14 celling voltage: The maximum direct voltage that the excitation system is designed to supply from its temminals under detned conditons.
NOTE 1-The noload ceiling voltage is detemined with the excitation system supplying minimal curren.
NOTE2-The ceiling voltage under load is determined with the excitation system supplying synchronous machine raled field cuurrent. NOTE3-Faran eucitatio system whose supply depends on the synchronous machine voltage and (if applicable) currentthe nature of power sysem disturbance and specifc design parameters of the encitation sysem and the syncronous machine intluencetheexctation sysem output For such systems, the ceiling volage is detennined codernga secied supely olageusaly raed woacc and spplicabici synchromoes mchine cu! NOTE4Forexciaionsysems employinga roating exciter, the ceiling voltage is deternined at rated speed
3.15 compound source-rectifer exciter: An exciter whose energy is derived from the currents and potentials ofthe ac terminals ofthe synchronous machine and converted to direct current by rectifiers. The exciter includes the power transformers (current and potential). reactors (if required), and rectifiers that may be either noncontrolled orcontrolled,including gate circuitry. It is exclusive of input control elements.
3.16 crowbar: In excitation system usage,a circuit designod to provide a conduction path for field current owto prevent excessive feld voltageTriggered semiconductors with serics resisors or inductors are commonly used.Non-linear resistors may abematively provide this function. NOTE-Sce Figure A.17b. 317 current boost An exciation system auxiliary supply that acts to increase the available power supplied to the field winding. typically during fault conditions where the terminal voltage is lower and current is higher than normal. 3.18 current beost exciter: An exciter whose energy is derived from currents at the ac terminals of the synchronous machine and converted to direct current by rectifiers. The current boost system output is added direetly with a potential source exciter rectifier as a separate rectifier system The current boost system mayinclude powercurentransformersand either noncontrolled rectifiers or controlled rectifiers, with gate circuitry.
IEEE 421.1-2007 pdf download
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