Overview Electrical Machines and Drives

Transcription

1 Overvew Electrcal achnes an Drves 7-9 1: Introucton, axwell s equatons, magnetc crcuts : agnetc crcuts, Prncples : Prncples, DC machnes : DC machnes an rves : I ntroucton, I prncples 25-9 Guest lecture Emle Brnk : I equvalent crcuts an characterstcs : I rves, S : S, PAC : PAC, other machnes 19-10: rest, questons 9-11: exam 1

2 Synchronous machnes Introucton, constructon Synchronous generators / motors Voltage equatons, equvalent crcuts an phasor agrams Power an torque characterstcs Capablty curves Spee control 2

3 Constructon Stator comparable to I: lamnate strbute stator wnngs Rotor hgh-spee: cylnrcal (p 4) wth strbute wnng low-spee lentpole (p 4) wth concentrate wnng 3

4 Synchronous machnes Introucton, constructon Synchronous generators / motors Voltage equatons, equvalent crcuts an phasor agrams Power an torque characterstcs Capablty curves Spee control 4

5 Synchronous generator p n n 60 1 p or 1 50Hz requency o the stator voltage or exctaton voltage synchronous spee o the rotor p n s (rpm)

6 P-pole machnes p s the number o poles (n some other books: number o pole-pars) N p N a ( θ ) sn( θ ) ˆ p B s ( θ, t) B cos( θ ωt) p θ θ 2 e m 6

7 Synchronous machnes Introucton, constructon Synchronous generators / motors Voltage equatons, equvalent crcuts an phasor agrams Power an torque characterstcs Capablty curves Spee control 7

8 Open crcut characterstc E 2π 1kw 1N1 2 Φ p 8

9 Poston n the gr 9

10 Connectng to the gr (nnte bus) Beore a synchronous machne can be connecte to the nnte bus, 1. voltage 2. requency 3. phase sequence 4. phase o the synchronous machne an the gr must be the me. 10

11 Synchronous motor connecte to the gr Not sel startng, thereore: - amper cage or asynchronous startng an ampng oscllatons - requency converter 11

12 Synchronous machnes Introucton, constructon Synchronous generators / motors Voltage equatons, equvalent crcuts an phasor agrams Power an torque characterstcs Capablty curves Spee control 12

13 Dervaton o voltage equatons The sketche stator an rotor wnngs are concentrate, but they represent strbute wnngs How can we erve voltage equatons an equvalent crcuts? 13

14 14 Voltage equatons t R u λ sr sc sb b b sc sr sc b sb b sb sr sc b sb b L L L ) ( ) ( ) ( π θ λ π θ λ θ λ 0 sc sb sr sc b sc sr sb b sb sr b L L L ) ( ) ( ) ( ) ( ) ( ) ( π θ λ π θ λ θ λ axwell, Faraay: No star-pont connecton

15 15 Voltage equatons, equvalent crcut c sc s sc sr sc s sc sc b sb s sb sr sb s sb sb a s sr s e t L R t t L R u e t L R t t L R u e t L R t t L R u ) ( ) ( ) ( π θ π θ θ b s L L Usng

16 Armature reacton The rotatng magnetc el conssts o two parts 1. the el create by the three-phase stator currents 2. the el create by the rotor exctaton Φ r Φ Φ a Generator conventon: λ E t E jωλ 16

17 Equvalent crcuts Generator conventon: λ E t E jωλ 17

18 easurng the synchronous nuctance 18

19 Phasor agrams Generator: V E RI jωl I t a s a otor: V E RI jωl I t a s a 19

20 Synchronous conenser Synchronous machne that behaves lke a capactor or nuctor may use or reactve power compenton n power systems has no mechancal loa Can you sketch the phasor agrams or capactve an nuctve operaton? 20

21 Synchronous machnes Introucton, constructon Synchronous generators / motors Voltage equatons, equvalent crcuts an phasor agrams Power an torque characterstcs Capablty curves Spee control 21

22 Power characterstcs R 0 Vt Vt E E (cos( δ ) jsn( δ )) s S V I V S (cos( δ ) jsn( δ )) V * t 3 t a 3 t j X s V E sn( δ ) V E cos( δ ) V 3 3 j X X 2 t t t s E s * Vt E P 3 sn( δ ) X s 22

23 Torque characterstcs T P ω m Vt E 3 sn( δ ) Tmax sn( δ ) ω X m s Stablty lmts Also or negatve loa angle 23

24 Torque-spee characterstc 24

25 Synchronous machnes Introucton, constructon Synchronous generators / motors Voltage equatons, equvalent crcuts an phasor agrams Power an torque characterstcs Capablty curves Spee control 25

26 Complex power locus S V E sn( δ ) V E cos( δ ) V 3 3 j X X 2 t t t s s What happens the power s ncrease? What happens the el current s ncrease? 26

27 Capablty curves Capablty s lmte by armature heatng el heatng steay-state stablty lmt 27

28 Synchronous machnes Introucton, constructon Synchronous generators / motors Voltage equatons, equvalent crcuts an phasor agrams Power an torque characterstcs Capablty curves Spee control 28

29 Spee control o synchronous machnes How can the spee o synchronous machnes be controlle? 29

30 Frequency control VSI s mportant. The cycloconverter s not scusse n ths course. 30

31 Flux weakenng 31

32 Overvew Electrcal achnes an Drves 7-9 1: Introucton, axwell s equatons, magnetc crcuts : agnetc crcuts, Prncples : Prncples, DC machnes : DC machnes an rves : I ntroucton, I prncples 25-9 Guest lecture Emle Brnk : I equvalent crcuts an characterstcs : I rves, S : S, PAC : PAC, other machnes 19-10: rest, questons 9-11: exam 32