Isolation Requirements in High Voltage Transformers

Thread Starter

JimmyCad

Joined Jul 1, 2019
6
Hi All,

I have a question regarding the insulation requirements of high voltage transformers and how they can be reduced. For an application that requires an output voltage of 5kV, the insulation should be higher than this, say 10kV or the like. I was wondering, is there any way transformers with lower insulation can be used? Here are some ideas that I had:

Centre-tapped secondary - I read on an article in regards to a HV application that having a centre tapped secondary reduces the insulation requirements of the transformer. Why is this so? There will still be the full voltage across the transformer, so why would the insulation requirement reduce?

Using voltage multipliers - if using voltage multipliers, the voltage at which the secondary is rated at is reduced, because the transformer is actually only subject to a smaller voltage than is actually present at the output. Therefore, can the insulation requirement be reduced in this way?

Using multiple transformers - if a transformer is to be rated at 700W power, with an output voltage of 5kV, required an insulation of 10kV. Would using two transformers connected in primary parallel, secondary series (PPSS) mean that the transformers would be each rated at 350W power, each delivering 2.5kV, and therefore the insulation requirements for the transformers reduce to 5kV each (2.5kV x 2).

It might be obvious that I'm a bit of a noob when it comes to transformer design, so these are just some ideas that I've had/seen in articles recently.

Sidenote: I won't be actually working at these voltages, just curious as to these points outlined above.

Thanks in advance.

Jim
 
Last edited:

Papabravo

Joined Feb 24, 2006
21,261
Keep thinking along those lines and you might be in the running for a Darwin Award.
They are normally awarded posthumously, but I notice that exceptions have been made.
 

Thread Starter

JimmyCad

Joined Jul 1, 2019
6
Keep thinking along those lines and you might be in the running for a Darwin Award.
They are normally awarded posthumously, but I notice that exceptions have been made.
I'm sure in the same breath you'll win the Nobel Peace Prize for being such a great person. Clearly you cannot read the text that appears before you create a reply to a thread. I did state that I am not new to this and needed help - but thanks for your "input" anyway. Have a great day.
 

shortbus

Joined Sep 30, 2009
10,049
I'm sure in the same breath you'll win the Nobel Peace Prize for being such a great person. Clearly you cannot read the text that appears before you create a reply to a thread. I did state that I am not new to this and needed help - but thanks for your "input" anyway. Have a great day.
Berating a well established member of the forum in your first few posts will take you far in your membership here.
 

Thread Starter

JimmyCad

Joined Jul 1, 2019
6
Berating a well established member of the forum in your first few posts will take you far in your membership here.
That's fair enough, but at the same time it's hardly fair to put someone down for actually attempting to put forward some ideas instead of just saying "give me a solution". It's only fair to expect to be berated in return if you are willing to be nasty to someone for absolutely no apparent reason.
 

Papabravo

Joined Feb 24, 2006
21,261
There is a reason and that reason is safety. You are starting a thread which suggests that cutting corners is an acceptable engineering activity. It is not. I leave it to the component engineers at the components company to provide me with components that are safe and effective. They do that job because they know I can buy components from their competitors. I may in fact test their devices to verify their claims, but I wouldn't think of asking them to cut corners and safety for a few pennies. That was my point. Go ahead and feel berated, it's nothing compared to doing what you did for a boss with high ethical standards. That'll get ya fired.
 

Thread Starter

JimmyCad

Joined Jul 1, 2019
6
There is a reason and that reason is safety. You are starting a thread which suggests that cutting corners is an acceptable engineering activity. It is not. I leave it to the component engineers at the components company to provide me with components that are safe and effective. They do that job because they know I can buy components from their competitors. I may in fact test their devices to verify their claims, but I wouldn't think of asking them to cut corners and safety for a few pennies. That was my point. Go ahead and feel berated, it's nothing compared to doing what you did for a boss with high ethical standards. That'll get ya fired.
You've clearly misunderstood - I am not cutting corners, I actually outline that I will not be working at these voltages whatsoever - I am purely talking theoretical. I suppose if I worked for a company and was trying to manufacture and sell engineering equipment that was obtained by "cutting corners" then you'd have a point - but I am not. I am a beginner in transformer design and was curious as to a few thoughts that I had, which to be honest I did think were not correct - hence why I asked here for clarification. Nowhere do I claim to be attempting to manufacture/profit/be deceitful to any customers or anything remotely of the sort.
 

WBahn

Joined Mar 31, 2012
30,243
MOD NOTE: The TS made it clear that this is a theoretical discussion only. It seems that they are simply trying to understand the issues that determine what rating is proper/needed in various configurations.
 

profbuxton

Joined Feb 21, 2014
421
It also depends on the primary voltage! Are you talking about step up or step down? Are you talking about power distribution txs?
Most power dist. txs have one side or other referenced to ground.
In your centre tapped case there is still 10Kv across the windings and depending on how its wound and internal clearances I would not want reduced insulation ratings.
In the case of series connection there also still 10Kv at the windings( one end connected to ground). Since either end may be grounded I would still want full insulation rating. I assume you mean 10Kv rms, remember peak voltage is much higher as is the test voltage for this stuff. .
I'm sure that experienced designers could come up with better answers and there are many years of designing and building txs that will explain the reasons for the insulation requirements
 
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