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Thoma-Type High Voltage Transformer

Thoma-Type High Voltage Transformer

Thoma-Type High Voltage Transformer

(OP)
Hi Electrical Gurus

I'm looking for a design specifications/text material on Column-Type Variable Transformers(CTVT) and Thoma-Type Variable Transformers(THVT).

I went thru lots of books stores , google them but couldn't find any good design document on these transformers.

I have one pdf from phenix but that is not very helpful.
If anyone of you can point me to a book/URL on the design of these transformers will be appreciated.

Thanks
praveen
 

RE: Thoma-Type High Voltage Transformer

(OP)
I'm looking for some positive replies.

RE: Thoma-Type High Voltage Transformer

Never heard of either one of those. Maybe you can provide us with a hint, like what are they used for?

RE: Thoma-Type High Voltage Transformer

Would have been really helpful if you had posted that link to start with. So what are you wanting to know? The literature seems to explain the operating concepts. Have you tried to contact the manufacturer with your question?
 

RE: Thoma-Type High Voltage Transformer

(OP)
I'm sorry for not posting itbefore, I'm looking for a design doc or some text material on that.Yes, I contacted them and this is what they provided.

I'm concerned about the text book if available. Are we on the same boat about voltage/variable?

Is one of your post holds good enough for this as well.

RE: Thoma-Type High Voltage Transformer

I know both types of variable voltage transformers from my work at former employers, but unfortunately I cannot recommed any freely available material neither as a link nor in written form.

These kind of transformers are quite an old technology that has been used to control plating rectifiers, induction furnances or to regulate fluctuating AC line voltage.

Nowadays such transformers are replaced by power electronic alternatives in most of the applications due to lower cost and better efficiency.

If, for some reason, you still need information how to design I'd recommend to visit a library and review books on transformers and electric machines of the time frame 1900 to 1980. It's very unlikely that you find approbiate information on the internet.

Contrary to the descripion from Phenix you posted, I know the Thoma-Regulator as a wound-rotor induction motor with locked rotor that is used as variable voltage transformer
 

RE: Thoma-Type High Voltage Transformer

(OP)
I appreciate your response and I'm not looking for any freely available material even if I have to pay some decent amount for that I won't hesitate as well , but I'm really interested in the material.
Let me know if you know some author who worked in this area.

RE: Thoma-Type High Voltage Transformer

Based on electricuwe's description of the Thoma-type regulator you may find more success searching for a "wound rotor" "induction regulator", including the "".
  

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If we learn from our mistakes I'm getting a great education!
 

RE: Thoma-Type High Voltage Transformer

agpreveen,

the reference that you have given doesn't seem to have any reference to thoma tranformers at all.

we use both thoma variable transformers (I'll call them regulators from here on) and column type regulators to control high voltage test transformers.  essentially they are descriptions for designs of large variacs.

The column type units are designed in a similar way to regular circular variacs (just with column type cores rather than toroidal), as they either roll a contact across the turns of the winding, or drag brushes across the turns.  This produces a stepped output voltage, with the step size being proportional to the number of turns on the output side.

Thoma type regulators are continously variable as they roll a contact around the copper winding (or actually roll the winding around the contacts, which is where the dollars get spent).  This means that there is no step in the output voltage as you increase or decrease the voltage.  Thoma style regulators are more expensive due to the design and manufacturing involved to create the continuous rolling contact arrangement.

When chosing a regulators for a test transformer, you must ensure that if you go for a "stepped" output that non-Thoma designs will give you, then the step size of the output voltage is acceptable.  For example, if your output voltage is variable from 0-500V, and this is feeding a 0-500kV test transformer, and your step size on the output of the regulator is say 5V (exagerated to show a point), then you will find your output voltage on the high voltage side of the transformer increases in steps of 5000V, which can give you problems.  This example is exagerated, but using stepped output regulators can lead to large uncertainty figures for testing.

I'm not sure why you need such detailed info, are you wanting to design one, or are you trying to compare them for an assignment?

ausphil
 

RE: Thoma-Type High Voltage Transformer

(OP)
ausphil,
i appreciate your detailed explanation....and it is really helpful...yes i'm planning to design one such transformer.....
and that is the reason i'm looking for a design doc or some text material.

thanks
agpraveen

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