Large Generator and High Power Drive Content of lecture 1. Manufacturing of Large Electrical Machine 2. Heating and cooling of electrical machine 3. Eddy current loe in winding ytem 4. Excitation of ynchronou machine 5. Deign of large ynchronou machine 6. Wind generator and high power drive 7. Force in big ynchronou machine Source: Siemen AG, Germany 4/1
4. Excitation of ynchronou machine 4.1 No-load and hort-circuit characteritic 4.2 Determination of neceary field ampere-turn 4.3 Phaor diagram of aturated ynchronou machine 4.4 POTER reactance 4.5 Stator current root locu Source: Neidhöfer, G., BBC, Switzerland 4/2
4. Excitation of ynchronou machine 4.1 No-load and hort-circuit characteritic No-load characteritic: - Stator open circuit - Rotor driven by auxiliary motor - Variable rotor excitation f - Stator: No-load voltage 0 i back EMF p Short-circuit characteritic: - Stator hort circuited - Rotor driven by auxiliary motor - Variable rotor excitation f - Stator: Steady-tate hortcircuit current k Synchronou reactance x d (per unit): x d = X d / Z N = 1/k k k k : No-load/hort-circuit ratio 4/3
4. Excitation of ynchronou machine No-load characteritic Meaured and calculated no-load characteritic: Line-to-line voltage veru field current at 3000/min, 50 Hz, 2-pole turbine generator, 400 MVA, co N = 0,75 cap. meaured X calculated Source: AEG, Germany 4/4
4. Excitation of ynchronou machine Saturation at no-load, no aturation at hort-circuit At tator hort circuit tator air gap flux linkage k = L d k i oppoite to rotor air gap flux linkage p = L d f. t nearly cancel rotor air gap field, o reulting air gap flux linkage h = L d m i mall ( magnetic operation point A ). A tator voltage i zero, induced tator internal voltage h = L d m mut balance voltage, which i induced by tator leakage flux: h = L d m = L k. So h i mall, iron i unaturated. 4/5
4. Excitation of ynchronou machine Meaured no-load and hort-circuit curve: 2000 MW generator S N = 2222 MVA, co N = 0.9 over-excited, 27 kv, Y, 50 Hz, 1500/min, N = 47.5 ka Olkiluoto 3: 2 GW turbo generator Source: Siemen, Germany 4/6
4. Excitation of ynchronou machine Meaured reactance: Turbine generator 2000 MW Olkiluoto 3: 2 GW turbo generator Source: Siemen, Germany 4/7
4. Excitation of ynchronou machine Tranfer ratio for rotor field current Amplitude and phae hift of p : may be decribed in equivalent circuit by fictive AC tator current f : X Thi define tranfer ratio of field current ü f : p h f f i the equivalent tator AC field current, that flow in tator winding and by elf-induction caue the ame back EMF p a the real rotor DC field current f doe by rotation of rotor. X h f f X h Example: Turbine generator: Rotor m.m.f. fundamental: Stator m.m.f. fundamental: p, B B p, N f Vˆ 2 f k p 2 mn Vˆ p wf k f w f Vˆ f Vˆ 1 ü f f we get: 1 ü f f ü f mnk 2N k f w wf 2 4/8
4. Excitation of ynchronou machine Fundamental of rotor field of turbine generator Example: q r =2 Rotor m.m.f. and air gap field ditribution have tep due to lot and contain fundamental ( = 1): Vˆ f Bˆ k k p 2 N f ( k p, f kd, f ) f p Vˆ f, N 0 f 2 p qr N fc in W f in( / 3) 2 p in( / 6) f, kwf k q in( /(6q )) p, Rotor field winding i one phae of a three phae ditributed winding, which i pitched by 2/3 and fed by DC current. d, r r pf 3 2 k df 4/9
4. Excitation of ynchronou machine Bruhle excitation armature and diode wheel Source: Siemen AG, Mülheim/Ruhr, Germany 4/10
4. Excitation of ynchronou machine Static excitation collector via two lip ring and carbon bruhe Source: Siemen AG, Mülheim/Ruhr, Germany 4/11
Large Generator and High Power Drive Summary: No-load und hort-circuit characteritic - No-load characteritic: Back EMF over excitation current at open-circuit - Non-linear voltage curve due to iron aturation - Short-circuit characteritic: Stator current over excitation current at hort-circuit - Small reulting air gap flux linkage No aturation -Back EMF p may be decribed by equivalent tator current: - Rotor excitation method: - External with lip ring and bruhe - Bruhle with rotation diode bridge f 1 ü f f 4/12
4. Excitation of ynchronou machine 4.1 No-load and hort-circuit characteritic 4.2 Determination of neceary field ampere-turn 4.3 Phaor diagram of aturated ynchronou machine 4.4 POTER reactance 4.5 Stator current root locu Source: Neidhöfer, G., BBC, Switzerland 4/13
4. Excitation of ynchronou machine 4.2 Determination of neceary field ampere-turn Calculation of magnetizing current, conidering main flux aturation: Magnetizing current Magnetic point of operation E of main air gap flux linkage h i determined by internal voltage: h h Thi i given for any arbitrary load (,, ) and determine magnetizing current: h X h m 4/14
4. Excitation of ynchronou machine Determination of field current f from phaor diagram - n order to get field current f from m, we need to know addition of tator and rotor current. - From phaor diagram we get f. With knowledge of ü f we calculate f. 4/15
4. Excitation of ynchronou machine Calculation of neceary field current for load point (,, ) A) B) A) n order to get field current f from m, we need to know addition of tator and rotor current. From phaor diagram we get f. With knowledge of ü f we calculate f. B) f machine i already built and meaured, we can take ü f from hort-circuit characteritic. t i the ditance between F and C, if the curve i given in dependence of f. 4/16
4. Excitation of ynchronou machine Calculation of field current for load point (,, ) in ONE diagram nput:,, u: under-excited, ü: over-excited Output: f 4/17
Large Generator and High Power Drive Summary: Determination of neceary field ampere-turn - Magnetic point of operation i determined by internal voltage h - Magnetizing current i read from the no-load characteritic h m ˆ 0 - Equivalent current f from phaor diagram - Tranfer ratio needed for determination of the excitation current - May be taken from the no-load/hort-circuit characteritic - ually calculation i done in ONE diagram f 4/18
4. Excitation of ynchronou machine 4.1 No-load and hort-circuit characteritic 4.2 Determination of neceary field ampere-turn 4.3 Phaor diagram of aturated ynchronou machine 4.4 POTER reactance 4.5 Stator current root locu Source: Neidhöfer, G., BBC, Switzerland 4/19
4. Excitation of ynchronou machine 4.3 Phaor diagram of aturated ynchronou machine Magnetic characteritic i linearized in magnetic operation point E to determine (fictive) back EMF for aturated load operation point. 4/20
Large Generator and High Power Drive Summary: Phaor diagram of aturated ynchronou machine - Linearization of the magnetic characteritic - Fictive back EMF in aturated load operation - n cae of load hedding: Terminal voltage i real no-load voltage, not fictive back EMF 4/21
4. Excitation of ynchronou machine 4.1 No-load and hort-circuit characteritic 4.2 Determination of neceary field ampere-turn 4.3 Phaor diagram of aturated ynchronou machine 4.4 POTER reactance 4.5 Stator current root locu Source: Neidhöfer, G., BBC, Switzerland 4/22
4. Excitation of ynchronou machine 4.4 POTER reactance n d-axi rotor tray flux f ~ f i ADDNG to main flux h, o it will increae pole haft iron aturation. Epecially at over-excitation (big f ~ f ) thi aturation may become very high. 4/23
4. Excitation of ynchronou machine Wort-cae over-excitation (maximum f ~ f ) at pure inductive load of ynchronou generator Phaor diagram for pure inductive load of generator at rated voltage and current: = N, = N, co = 0 over-excited C Due to thi big rotor tray flux the rotor iron aturate trongly, yielding an increaed demand of excitation ampere-turn f. H d 2 N f pole f 2N f, (, pole f f ) 4/24
4. Excitation of ynchronou machine ncreaed demand of field current i conidered in phaor diagram by POTER reactance X P intead of tator leakage reactance X Pole haft aturation i maximum at pure rated inductive load 4/25
4. Excitation of ynchronou machine POTER reactance X P - ncreaed iron aturation will lead to decreae in main reactance. - ually thi influence i not conidered by reducing main reactance, but by introducing POTER reactance! - ncreaed field current give (at fictively contant main reactance X hd ) a fictively increaed back EMF p. Thi ha to be compenated by a fictively increaed leakage reactance X, which i called POTER-reactance X P : p X hd f p X hd f h X hd m X P X 4/26
4. Excitation of ynchronou machine Meauring POTER reactance with method of FSCHER-HNNEN RP f - No-load & hort-circuit characteritic are meaured and field current for pure inductive rated load (RP) - Magnetic point of operation E of internal voltage h include terminal voltage N and voltage drop X P N - Subtracting from field current f the tator current N. ü f yield magnetizing current m. ü f, o we get h ( m ) = 0 ( m ) from no-load characteritic. - N. ü f i viible in hort-circuit characteritic. There iron i unaturated, o X P N = X N. - Paralleling unaturated no-load characteritic and ampere-turn of hort-circuit condition i alo poible to determine h, intead of taking N. ü f (which need knowledge of ü f ) 4/27
Large Generator and High Power Drive Summary: POTER reactance - Rotor tray flux i adding to main flux in d-axi - ncreaed iron aturation of the pole haft - ncreaed demand of excitation ampere turn - Wort cae: Over-Excited pure inductive load - The influence i conidered by introducing POTER reactance X P X - Meaurement via the method of FSCHER-HNNEN for pure inductive rated load (RP) 4/28
4. Excitation of ynchronou machine 4.1 No-load and hort-circuit characteritic 4.2 Determination of neceary field ampere-turn 4.3 Phaor diagram of aturated ynchronou machine 4.4 POTER reactance 4.5 Stator current root locu Source: Neidhöfer, G., BBC, Switzerland 4/29
4. Excitation of ynchronou machine Cylindrical rotor ynchronou machine: (R 0, = cont., p = cont.) ( X ) d 4.5 Stator current root locu X p d e 4/30
4. Excitation of ynchronou machine Stator current root locu of cylindrical rotor ynchronou machine - neglected tator winding reitance R 0, - tator grid voltage i contant = cont., - different excitation level f ~ p 4/31
4. Excitation of ynchronou machine Operational limit of the cylindrical rotor ynchronou machine 1) Max. exciter current 2) Max. tator current 3) Max. load angle (< 90 ) 4) Minimum exciter current 5) Max. real power 4/32
4. Excitation of ynchronou machine Real and reactive power limit of the cylindrical rotor ynchronou machine P Q m m N N N co in S m N P / S Re / N m m N N N N Re m N ~ Re ~ m Q / S m / The power limit i directly proportional to the tator current limit! N Over-excited = capacitive nder-excited = inductive Conumer reference = negative real power in generator mode Example: 2-pole turbine generator A: Thermal limit of exciter winding ( f,max ) B: Thermal limit of tator winding (,max ) C: Ditance to tability limit D: Rated power: co = -0.9 overexcited 4/33
4. Excitation of ynchronou machine Regulation curve and V-curve of a cylindrical rotor ynchronou generator Curve can be directly taken from the tator current root locu diagram: Regulation curve: ( f ) for co = cont. V-curve: ( f ) for Re = cont. Re co 4/34
4. Excitation of ynchronou machine Regulation curve and V- curve of a ynchronou motor Regulation curve: ( f ) for co = cont. V-curve: ( f ) for Re = cont. P m Re cont N. Operation of the motor at the rigid grid: = cont. Data: x d =X d /Z N = 1.33, k K =1/x d = 0.75, No-load exciter current: f0 4/35
4/36 4. Excitation of ynchronou machine Contruction of the tator current root locu of a alient pole ynchronou machine, R = 0 (1) e p p e e e e 2 co q e e e e ) ( 2 ) ( in d d d p q X 2 p d d p q d e e X e X 2 q q d q q q d e e X e X X ) 1 1 ( 2 ) 1 1 ( 2 d q 2 q d d p q d X X e X X X e
4/37 4. Excitation of ynchronou machine Contruction of the tator current root locu of a alient pole ynchronou machine, R = 0 (2) ) 1 1 ( 2 ) 1 1 ( 2 d q 2 q d d p X X e X X X e
4. Excitation of ynchronou machine Stator current root locu of alient pole ynchronou machine - neglected tator winding reitance R 0, - tator grid voltage i contant = cont., - different excitation level f ~ p 4/38
4. Excitation of ynchronou machine Stator current root locu of alient pole ynchronou machine w Re b m 4/39
Large Generator and High Power Drive Summary: Stator current root locu - Cylindrical rotor machine: circle with radiu proportional to f (for R = 0) - Operational limit: min./max. exciter current, max. tator current, max. load angle, max. real power, tability limit - Salient pole machine: Pacal limacon - For zero excitation: Reluctance circle - Regulation curve: ( f ) for co = cont. -V-Curve: ( f ) for Re = cont. 4/40