Lamalam
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The note said ythat I should use thick copper wire to reduce resistance and hence the energy loss.

However for point 3, it also stated that I need to use laminated core to givw high resistance. Aren't they contradict each other?

And will the increase in resistance prevent the channeling of the magnetic field by the core?

Thank you!

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Zenarthra
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(Original post by Lamalam)
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The note said ythat I should use thick copper wire to reduce resistance and hence the energy loss.

However for point 3, it also stated that I need to use laminated core to givw high resistance. Aren't they contradict each other?

And will the increase in resistance prevent the channeling of the magnetic field by the core?

Thank you!

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I think eddy current causes the the core to heat up and energy is lost.
If you use a laminated core with high resistance, no current can flow therefore less energy lost.

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Lamalam
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(Original post by Zenarthra)
I think eddy current causes the the core to heat up and energy is lost.
If you use a laminated core with high resistance, no current can flow therefore less energy lost.

where does the energy come from? the primary power supply in the transformer??
and I am confused because copper wire is desired to be thick to reduce the resistance and now I need to get high resistance
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Fysiika07
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there are two elements in a transformer, the core and the copper wires wrapped around the core. the copper wires are for current to flow in primary and secondary coil respectively. the core is to channel the magnetic field from primary to secondary coil. as magnetic field flows through the core, eddy current generated in there, wasted as heat. Therefore, for higher efficiency, core consists of laminated metal piece, while copper wire in primary and secondary coil should have larger diameter.
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Lamalam
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(Original post by Fysiika07)
there are two elements in a transformer, the core and the copper wires wrapped around the core. the copper wires are for current to flow in primary and secondary coil respectively. the core is to channel the magnetic field from primary to secondary coil. as magnetic field flows through the core, eddy current generated in there, wasted as heat. Therefore, for higher efficiency, core consists of laminated metal piece, while copper wire in primary and secondary coil should have larger diameter.
It seems to me that the heat generated in core comes from nowhere? am I wrong?? or the heat is supplied by the primary coil?

will the eddy current affect the channeling of magnetic field in core?

thank you!
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uberteknik
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(Original post by Lamalam)
It seems to me that the heat generated in core comes from nowhere? am I wrong?? or the heat is supplied by the primary coil?
There are several sources for power losses in a power transformer:

I2R copper losses in the primary and secondary windings.
Eddy current losses
Hysteresis losses

But of all these, the biggest contributor is the I2R copper loss.

Copper losses:

These vary with the load connected to the secondary winding.

On the one hand, to deliver the maximum power to the load, the coil windings should be as low resistance as possible. However since current is dependent on resistance (I = V/R), and power = I2R, as the winding resistance reduces, the power dissipated in the coil windings goes up exponentially.

Eddy Currents:

The primary coil generates a magnetic field exactly the same way as a solenoid does. In fact, the transformer core is a solenoid core.

Because the core is made of iron, it is also a conductor and hence currents will also flow in the core.

But a solid core has a very low resistance (<<1 ohm) and the currents induced in the core will therefore be very high (I = V/R).

Waste heat is generated by core resistive losses: Power = I2R and as the core resistance falls, the power dissipated in the core goes up exponentially.

So in order to reduce those resistive power losses, the core is laminated to ensure any circulating eddy currents are confined to a small area (higher resistance). The induced currents circulating within the core are significantly reduced and consequently power losses are also significantly reduced.

Eddy current losses do not depend on the transformer secondary load and remain constant as they are a function of the primary coil only.

Hysteresis losses:

First magnetising and then demagnetising the core cyclically at the same frequency as the AC in the primary winding, will consume power because of core remanence and coercivity.

Hysteresis losses are a function of the core magnetic properties and magnetising current.



(Original post by Lamalam)
will the eddy current affect the channeling of magnetic field in core?
It has a very slight affect because the magnetic domains in the core are now slightly more seperated by the laminations. Hence this almost negligibly reduces the strength of the B field in the core.

In high power applications, copper losses and to a lesser extent eddy current power losses are significant, which is why high power transformers are forced air cooled, water cooled or immersed in oil and fitted with large cooling heatsinks to dissipate the heat generated.

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