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SINGLE
PHASE
TRANSFORMERS
1
1. components:
-- 2 adjacent coils
-- coils not physically connected to each other
2
2. operation:
a) AC in primary coil produces ∆ B
b) Secondary coil receives a ∆ in I & V
3
N
SN
SN
SN
SN
SN
S
N n
A
B
C
a
b
c
IA Ia
VAN
VAB
VCN
VBN Vbn
Van
Vcn
Vab
4
Wye / Wye connection
Load
Supply
Network
Transformer
Y-Y
Transformer LoadSupply Network
Xtr_s
Van Vload_an
VAN
Vnet_AN
Xnet
IA
Ia
N
n
A
a
5
Thr...
Wye / Delta connection
6
A
B
C
N
VAN
VAB
VBN
VBC
VCN
IA
Iba
Icb
VCA
a
b
c
a
b
c
Ia
Ic
Ib
Vab
Vbc
Vca
Iac
Ia
Ib
Ic
Vab
Vbc
Vca
VCN
VBN
VAN
A
B
C
a
b
c
Icb
Iba
Iac
Transformer
AC
AC
AC
IC
IB
IA
VAN
VBN
VCN
Supply
Iab
Ibc
Ica
Load...
Xtr_s
Van Vs_an
VAN
IA Ia
Vp_AN
Xtr_p
Rtr_p
Rtr_s
Xm
Rc
Tspe
Y-∆
8
Single-phase equivalent circuit of a wye-delta transfor...
Delta / Wye connection
9
A
B
C
n
a
b
c
VBC
IaIA
Ib
Ic
VAB
VCA
Vca
Vab
Vbc
Van
Vbn
Vcn
IC
IB
ICA
IAB
IBC
Delta / Delta connection
10
A
B
C
a
b
c
VAB
Ia
Iba
Iac
IA
IAB
ICA
Vab
 ratio of the # of turns in the
secondary coil to the # of turns in
the primary coil
11
P
S
N
N
TR =
 numerical factor i...
 ∆ in V is directly proportional to the ratio of
the # of turns in the secondary to the # of turns
in the primary
 Formu...
 Current in a transformer will be inversely
proportional to the TR of the transformer
 formula:
13
N
N
I
I
S
P
P
S
=
V
V...
 Based on TURNS RATIO
14
2. step-down
turns ratio < 1
VS < VP
IS > IP
1. step-up
turns ratio > 1
VS > VP
IS < IP
1. air core
--inside area of coil is
empty
-- inefficient induction
15
2. open core
-- ferromagnetic
material inside coils...
3. closed core
-- ferromagnetic ends
connected
-- ↑Β = ↑ induction
16
4. shell
-- lazy square eight
-- overlap of coils on...
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Transformer

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Transcript of "Transformer"

  1. 1. SINGLE PHASE TRANSFORMERS 1
  2. 2. 1. components: -- 2 adjacent coils -- coils not physically connected to each other 2
  3. 3. 2. operation: a) AC in primary coil produces ∆ B b) Secondary coil receives a ∆ in I & V 3 N SN SN SN SN SN S
  4. 4. N n A B C a b c IA Ia VAN VAB VCN VBN Vbn Van Vcn Vab 4 Wye / Wye connection
  5. 5. Load Supply Network Transformer Y-Y Transformer LoadSupply Network Xtr_s Van Vload_an VAN Vnet_AN Xnet IA Ia N n A a 5 Three-phase network supplies a load through a transformer. Xtr_s Van Vload_an VAN IA IaVnet_AN Xnet Equivalent circuit of the wye-wye Single-phase equivalent circuit for phase A of the three-phase wye-wye transformer system
  6. 6. Wye / Delta connection 6 A B C N VAN VAB VBN VBC VCN IA Iba Icb VCA a b c a b c Ia Ic Ib Vab Vbc Vca Iac
  7. 7. Ia Ib Ic Vab Vbc Vca VCN VBN VAN A B C a b c Icb Iba Iac Transformer AC AC AC IC IB IA VAN VBN VCN Supply Iab Ibc Ica Load VAB VBC VCA Iac Vca Vbc Vab N 7 Wye-delta connected transformer
  8. 8. Xtr_s Van Vs_an VAN IA Ia Vp_AN Xtr_p Rtr_p Rtr_s Xm Rc Tspe Y-∆ 8 Single-phase equivalent circuit of a wye-delta transformer.
  9. 9. Delta / Wye connection 9 A B C n a b c VBC IaIA Ib Ic VAB VCA Vca Vab Vbc Van Vbn Vcn IC IB ICA IAB IBC
  10. 10. Delta / Delta connection 10 A B C a b c VAB Ia Iba Iac IA IAB ICA Vab
  11. 11.  ratio of the # of turns in the secondary coil to the # of turns in the primary coil 11 P S N N TR =  numerical factor indicating relative change in PD across a transformer TR > 1 = V (step up) TR < 1 = V (step down)
  12. 12.  ∆ in V is directly proportional to the ratio of the # of turns in the secondary to the # of turns in the primary  Formula: 12 N N V V S P S P = NS secondary coil turns NP primary coil turns VS secondary voltage VP primary voltage direct relationship
  13. 13.  Current in a transformer will be inversely proportional to the TR of the transformer  formula: 13 N N I I S P P S = V V I I S P P S = IP primary coil current IS secondary coil current  I vs. V = inverse relationship
  14. 14.  Based on TURNS RATIO 14 2. step-down turns ratio < 1 VS < VP IS > IP 1. step-up turns ratio > 1 VS > VP IS < IP
  15. 15. 1. air core --inside area of coil is empty -- inefficient induction 15 2. open core -- ferromagnetic material inside coils -- ↑B = ↑induction
  16. 16. 3. closed core -- ferromagnetic ends connected -- ↑Β = ↑ induction 16 4. shell -- lazy square eight -- overlap of coils on same ferromagnetic core
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