Basic Concepts of A Machine

Transcription

1 asic Concepts of A Machine

2 asic Concepts of A Machine (1) tator: stationary portion of the achine Rotor: rotating portion of the achine haft: the stiff rod that the rotor is ounted on Air gap (Gap): between stator and rotor

3 asic Concepts of A Machine (2) Load current: the current that varies with load Magnetizing current: provide agnetic field and independent of load Arature: the winding that carries only load current Field: the winding that carries only agnetizing current dc achine: the input/output current is dc ac achine: the input/output current is ac; two categories: synchronous achine induction achine (no field winding, siilar to transforer)

4 asic Concepts of A Machine (3)

5 asic Concepts of A Machine (4) round rotor salient pole rotor

6 Electrical vs Mechanical Frequency N N N N At steady state echanical speed f n f e 2 f revolution/inute (rp) n 1 60 n 60 rev/second

7 lots and Coils (1) Double Layer Lap Winding botto top tooth slot top botto

8 lots and Coils (2) coil end coil side coil leads coil side coil end Nc turns, 2Nc conductors

9 On arature lots and Coils (3) Each slot has 2 positions: top and botto (double layer winding) Each coil needs to occupy 2 positions: top position of one slot and botto position of another slot Nuber of arature coils = Nuber of arature slots () phase achine: Nuber of coils per phase: ph Nc Nuber of turns per phase: Nph phnc Nc 2 Nuber of conductors per phase: Cph 2 Nph = Note: The above three equations are independent of the nuber of poles (). For balanced -phase design, ph should be an integer.

10 3 phase, 24 slots lots and Coils (4) 8 coils, 8N c turns, 16N c conductors per phase 13 N ph N c turns N ph / 2 4 N c turns pole, hase A, full-pitch 4 pole, hase A, full-pitch

11 lot itch lot pitch in electrical angle is defined by 2 where is the echanical angle between two adjacent slots: 2 The slot pitch is also defined as the arc length between two slots on stator inner circle (with diaeter D): s D phase, 24 slots, 2 pole hase A, full-pitch D

12 360 o ole itch ole itch: angular distance between two adjacent poles on a achine. 2 (in echanical degree) Regardless of the nuber of poles on the achine, a pole pitch is always 180 o or in electrical degrees. The pole pitch is also defined as the arc length between two adjacent poles on stator inner circle (with diaeter D) : D (in eter or inch) Nuber of lots per ole: Note: ay not be an integer. 36s8p

13 Coil itch Full-itch Coil: If the arature coil stretches across the sae angle as the pole pitch, it is called a full-pitch coil. The coil spans across slots, if is an integer. Fractional-itch Coil: If the arature coil stretches across an angle saller than a pole pitch, it is called a fractional-pitch coil (or shortpitched coil, chorded coil). The coil spans less than slots. Let c be the nuber of slots that the coil spans. Let be the echanical angle that the coil spans or c. Coil pitch in electrical angle is defined by c 2

14 Fractional itch Coil (1) slots, 2 pole, 3 phase hase A, full-pitch hase A, (11/12)-pitch o o

15 Fractional itch Coil (2) 24 slots, 4 pole, 3 phase hase A, full-pitch o o hase A, (5/6)-pitch o 75 5 o 150 6

16 Group (1) 4 pole, 3 phase, 24 slot achine hase A, (5/6)-pitch This group consists of 2 coils. q Nuber of tator lots ( ) Nuber of coils per group: Nuber of phases ( ) Nuber of poles ( ) q Nuber of coils = Nuber of slots for double layer winding Nuber of groups = Nuber of poles () for double layer winding 3 for 3 phase achine

17 q can take fractional nuber Group (2) 18 q q pole, 3 phase, 18 slot 2 pole, 3 phase, 9 slot

18 UCF Torque T T R F 0 R F How to understand torque: ut the thub in the direction of torque. The other four fingers point to the direction of rotation. wrench on a nut

19 UCF Torque fro a Current Loop loop df1 Idxax Idx( yaz za y) 1 R1 dya y 2 1 dt1 R1 df1 dya y Idx( yaz za y) 2 1 dxdyiya x 2 1 dt3 R 3 df3 dya y ( Idx)( yaz za y) 2 1 dxdyiyax dt1 2 dt dt dxdyi a 1 3 Likewise y x dt2 dt4 dxdyixa y Idxdy( a ) Id z Note: Define d is in the sae direction of loop and both are proportional to I d Id d d dt d = k loop T k loop

20 UCF Torque roperty of a Machine (1) sin R R k T k T ince R net sin ) ( net R net R R net R k T k k T

21 UCF Torque roperty of a Machine (2) R net 6 pole synchronous achine

22 UCF Torque roperty of a Machine (3) otor T k R generator