Download presentation
Presentation is loading. Please wait.
1
MARK LEAKEY KOK WAI, WONG WAN HAZLIN ZAINI
TRANSFORMERS MARK LEAKEY KOK WAI, WONG WAN HAZLIN ZAINI Reference :
2
DEFINITION Device used to transfer energy from primary winding to secondary winding by electromagnetic induction. Based on Faraday’s Law of induction Where:- ε – EMF (V) ΦB – Magnetic flux (Wb)
3
TRANSFORMER USES Impedance matching Electrical Isolation
AC power transmission STEP-UP Transformer STEP-DOWN Transformer
4
HISTORY 1831 – Michael Faraday invented the Induction Ring.
1881 – Lucien Gaulard and John Gibbs exhibited a device called secondary generator. 1885 – William Stanley developed the fist commercially used practical device while working for Westinghouse Electric Company in US.
5
INDUCTION THEORY ε – EMF (V)
Transformers behaviour is based on Faraday’s Law of Induction Where:- ε – EMF (V) N – No of turns of wire ΦB – Magnetic flux (Wb)
6
INDUCTION THEORY Reference:
7
TRANSFORMER MODELS Ideal Transformer
Np = No of windings on the primary Ns = No of windings on the secondary ip = Current into the primary is = Current out from the secondary Vp = Voltage across the primary Vs = Voltage across the secondary
8
Primary and Secondary Relationship
VP = NP = a = iS VS NS iP Note; a < 1 = Step up transformer a > 1 = Step down transformer Voltage and current angles are NOT affected hence, θP = θS = θ
9
LOSSES Transformers have losses and these losses must come into consideration. Copper losses (I^2 R) Leakage Flux losses Core losses Eddy currents Hysteresis losses
10
REAL TRANSFORMER LOSSES
Copper losses (I^2 R) Leakage Flux losses Core losses Eddy currents Hysteresis losses
11
Approximate Transformer Model referred to the primary side
EQUIVALENT CIRCUIT Approximate Transformer Model referred to the primary side
12
TYPES Auto-Transformer
Used to change a desirable voltage by only a small amount. For example: 120/132 V IH VL VSE NC NSE VH ISE IL
13
Three Phase Transformers
TYPES Three Phase Transformers Three phase transformers can be constructed in two different ways i.e. :- A three phase bank consists of three single phase transformers. Three windings wrapped around a common core. Reference : Electric Machinery and Power System Fundamentals, Stephen J. Chapman
14
THREE PHASE TRANSFORMER CONNECTIONS
Delta – wye (Δ – Y) Delta – delta (Δ – Δ) Wye – delta (Y- Δ) Wye – wye (Y – Y) Reference : Electric Machinery and Power System Fundamentals, Stephen J. Chapman
15
TYPES Two types of special purpose transformers used in power systems for taking measurements. Potential Transformer Current Transformer Reference : Electric Machinery and Power System Fundamentals, Stephen J. Chapman
16
EFFICIENCY Efficiency (η) is the ratio of the power out to the power in of a transformer. η in an Ideal transformer, no power losses PIN = VPIP cos θP POUT = VSIS cos θS PIN = POUT = VPIP cos θP = VSIS cos θS SOUT = SIN = VPIP = VSIS ηIdeal = 100%
17
Efficiency for a single phase real transformer
As mentioned previously, losses occur in a real transformer and these losses must be taken into count. Hence, ηReal = POUT x 100% PIN = POUT x 100% POUT + PLOSS = VSIS cos θS_________ VSIS cos θS + i2R + (VP/a)2 RC
18
VOLTAGE REGULATION Voltage regulation (VR) is the ability of a system to provide near constant voltage over a wide range of load conditions. Also it compares the VO at no load to VO at full load. An Ideal transformer has a voltage regulation, VR = 0% Reference :
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.