Transformers

Wednesday, 20 March 2019

5:29 PM

Symbols//

Air core - nothing in between

Ferrite core - double dashed line

Iron core - double solid line

 

Flux Leakage//

Flux leakage occurs when part of the flux breaks out of the core, reducing the output of the secondary coil

 

 

 

 

 

An Ideal Transformer

• Windings have no resistance
• Perfect coupling ()
• Permeability of the core is infinitely large
• Core losses are neglected

 

Instead of a mutual inductance arrow, there is a primary coil turn to secondary coil turns ratio (physically) above

 

 

 

The load  in a secondary circuit of a transformer is reflected into the primary circuit by transformer action

 

 

 

 

Reflected impedance

 

 

 

 

Oppositely wounded transformers - 180 degrees out of phase

 

Dot Rule for Transformers

 

 

If I_1  and I_2 both enter into or both leave the dotted terminals, use - turns ratio

If V_1 and V_2 are both positive or both negative at the dotted terminals, use + for turns ratio