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Q & A: superconducting transformers

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Most recent answer: 02/16/2011
Q:
What is the benefit of a superconducting transformer? I once asked a transformer factory and they claimed that the core material was far more important than the coil material.

On the other hand, how would the core material be affected if it is being cooled to cryogenic temperature? Could the performance of the core material be actually lowered by such a low temperature?
- Joseph (age 30)
A:
I assume that the issue here is how to prevent losses., i.e. the dissipation of energy. These occur by
1. Electromagnetic radiation
2. Electrical resistance of the wires
3. Lagging response in the core.

No doubt that manufacturer was right that for typical applications the core response is most important. However, superconducting transformers not only eliminate the electrical resistance in the wires but also allow the construction of useful transformers without a core. The core will generate heat as the magnetic domains are constantly flipped in the alternating field of the windings of the transformer, and this is the biggest energy loss in most practical transformers.

To explain, the main role of the magnetic core is to allow much larger magnetic fluxes to be created by a given current. (The core also helps guide the flux between coils in some transformers.) Now the main point of that is to transfer more power to the secondary for a given power to the primary. The primary dissipates power mainly because of its electrical resistance. In a superconducting transformer the primary dissipates no power except for a small electromagnetic radiation term, so near 100% efficiency can be obtained with no core at all. That's a pretty effective way to eliminate core losses.

Mike W.

(published on 10/22/2007)

Follow-Up #1: superconducting transformer

Q:
how superconducting transformer is constructed without core
- Sreevani (age 21)
Hyderabad,AP,India
A:
So long as the secondary stays superconducting, its net flux cannot change, since no magnetic field lines cross the superconductor. (Here we need for it to be Type I or Type II below the lower critical field.)  As the current in the primary changes, that would make flux changes in the secondary. The secondary makes currents to cancel that flux.

Mike W.

(published on 06/07/2010)

Follow-Up #2: superconducting transformer

Q:
what exactly is a superconducting transformer?what does it do?sir actually i have a technical seminar about the topic in our college.so need to explain it briefly.pls help.thanking you in advance!!!
- vishwanath (age 20)
hyderabad,andhra pradesh,india
A:
Let's fill in the previous explanations.

Take a coil of superconducting wire looped near another superconducting coil. As current flows through the first, that would make a magnetic field on the second. However, at low field conventional superconductors do not allow any magnetic field to penetrate. The way that the field on the second coil can be kept to zero is for just the right current to flow in it to make a field to cancel the field from the first coil. So a current in the first coil forces there to be a current in the second coil.

Among the advantages of this is that it actually works dc, not just ac, unlike a standard transformer.

Mike W.

(published on 02/15/2011)

Follow-Up #3: superconducting transformer

Q:
Is there any difference between a HTS Transformer and a Superconducting Transformer or are they the same??
- vishwanath (age 20)
hyderabad,andhra pradesh,india
A:
I assume the HTS stands for high-temperature superconductor.  A transformer of that type operates in the same way as a low-temperature superconductor. Each superconductor has its own maximum magnetic field and current density at any particular temperature, so there are practical differences between them. The huge advantage of the HTS is that it may operate at liquid nitrogen temperature, and liquid nitrogen is cheap and easy to store.

Mike W.

(published on 02/16/2011)

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