Name of the staff member: A. Siva Sankar, L/EEBranch :Electrical and Electronics Engg.Name of the institution: Govt.ol!technic, roddaturSemester : "#$a%or &o'ic : Single hase &ransformersSub(&o'ic : "deal transformer on loadSub.)ode*&itle : EE+,-.* A) $achines+"/uration : 0- min.&eaching Aids:&, Animations1 EE 403.11DEPARTMENT OF TECHNNICAL EDUCATION ANDHRA PRADESH Recap 1"n the 'revious class the 2orking of ideal transformer on no+load 2as discussed.1&he 'rimar! current on no+load 2as onl! to set u' flu3 in the core and to meet the iron losses.1"n this session the change of currents and flu3 in the core, and voltages 2hen the transformer is loaded is to be discussed.2 EE 403.11Objective:Objective:4n com'letion of this 'eriod !ou 2ill be able to understand1 5hat is ideal transformer61 &he o'eration of ideal transformer onload.1&he develo'ment of 'hasor diagrams3 EE 403.11Ideal tran!"r#er:Ideal tran!"r#er:1&he theor! of o'eration of a transformer is best understood b! vie2ing the transformer as an ideal device.1An ideal transformer has no losses1&he 'rimar! and secondar! 2indings have 7ero resistance1&he leakage of the 2indings is 7ero1&he 'ermeabilit! of the core is infinit!4 EE 403.11Ideal tran!"r#er "n l"ad:Ideal tran!"r#er "n l"ad:Whenthetransformerisconnectedtosupplysource,the primarywindingdrawingcurrentI0setsupafluxin the core as shown in fig.(a).Fig (1): Ideal transformerwhen primary is only excitedI05 EE 403.115hen transformer is loaded, the secondar! current 8"9: is set u'. &he 8"9: sets u' its o2n flu3 ;9 o''osing the main 'rimar! flu3;< as sho2n in figure=b>.?ig =9>: &ransformer on load @ ;9 established6 EE 403.111 5henthe secondar! flu3 o''oses the 'rimar! flu3, the reduction in the net flu3 in the core causes to dra2 an e3tra current from the su''l! kno2n as load com'onent of 'rimar! current "9:1&he additional 'rimar! mmf =N9"9:> set u' a flu3 ;9: 2hich is eAual and o''osite to ; as sho2n in fig B.Fig (): !"# neutrali$ing the !"7 EE 403.11Since ;9 C ;9: , the net flu3 in the core is, therefore, the same as at no+load as sho2n in fig =d>&herefore ,", inductive=lagging ?> or ca'acitive=leading ?>.11 EE 403.11P$a"r Dia%ra# "! Ideal tran!"r#er !"r reitive l"ad :V1I2E2I2I0=II10= 901Fig ' : phasor diagram for resisti(e load12 EE 403.11P$a"r Dia%ra# "! Ideal tran!"r#er !"r ind&ctive l"ad10= 902V1E2I2I2I0=II1Fig ()): phasor diagram for inducti(e load13 EE 403.11P$a"r Dia%ra# "! Ideal tran!"r#er !"rCapacitive l"ad0= 90E222I0=IV1I2I21I1Fig (*): phasor diagram for capaciti(e

load14 EE 403.11&he follo2ing figure sho2s the 'hasor diagram of ideal transformer for inductive load 2here the no+load current "- is neglected2V1E2I2I2 I1=2Fig (+): phasor diagram of ideal transformer for inducti(e load15 EE 403.111 As no+load current is 9+0G of rated current , it can be neglected.1 &herefore," .- degreesb> K- degreesc> L0 degreesd> NoneIF"J.. &he mutual flu3 in the core of a transformer ++++++++++++++++a> "s al2a!s constant b> #aries 2ith loadc> /e'ends u'on the su''l! voltaged> /e'ends u'on the turns ratio 20 EE 403.11IF"J,. &he 'rimar! current of a transformer is 0A. &he secondar! current, if the transformation ratio is ,, is++++++++++++++++++++++++a> 9- A b> H-A

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