transformer turns ratio and core losses

Thread Starter

logicman112

Joined Dec 27, 2008
69
Does the turns ratio of a transformer effect the core losses?

When 220 volts AC is connected to a simple DC adaptor, it heats the transformer(maybe because the turns ratio is high), but how if the turns ratio is 1:1?

The transformer will become cooler?
 

t_n_k

Joined Mar 6, 2009
5,448
Core losses are all related to the magnitude and rate of change of the core magnetising flux.

The number of turns on the primary (exciting) winding are important insofar as they determine the magnetising flux for the given physical core properties, applied primary AC voltage and operating frequency.

Turns ratio has no direct effect on core losses.
 
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Thread Starter

logicman112

Joined Dec 27, 2008
69
thank you for the reply. What are the magnetizing flux and current?

Hysteresis loss is the energy that is consumed to change the orientation of magnetics domains. When magnetic orientation changes, the core is magnetised and we have a total flux named Qm inside the core.(Qm is the total flux resulted from i1 and i2, the currents of primary and secondary windings).

So why the core still needs an extra current named im (magnetisation current) to be magnetised? (does the electromagnetic rules dictate the existence of such current?) and where is the magnetisation flux? Is it part of Qm?
 

t_n_k

Joined Mar 6, 2009
5,448
The classic form of Faraday's Law of induction as it relates to transformer magnetisation is given by

\[V_{rms}=4.443fN\Phi_{max}\]

This shows the relationship between the applied primary rms voltage and the peak core flux occurring in a sinusoidally excited transformer. The other parameters are the number of primary winding turns [N] and the sinusoidal frequency [f].

As you can possibly see, one doesn't need to consider the current at all.
 
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