Need 4KV isolation

Thread Starter

mohan.n2293

Joined Jan 23, 2017
60
HI All,
how to know the isolation Between each pin of transformer.
let us take i need 4kv isolation between each pin what should be the pitch between each pin.
 

Janis59

Joined Aug 21, 2017
1,232
For 4 kV is every kind of insulation materials available, its not a 50 kV where only few good alternatives exist.
One is floor linoleum, those white colour elastic with no threads or textile inside. It stand at 2,5 mm thick about 40 kV. Other is teflon, even more strong. The ebonit (hard rubber) and getinax (paper in fenolic resin) - at least 8...10 kV is realistic for them. The PPE, PET, plexyglass, polystirol - good up to 10 kV, but last not likes the frequeancy over 30 MHz. Glass, quartz, ceramics - very strong and good, but difficult to form, need a diamond ring or torch. Powders like white-clay or silicon sand or MgO or AlO2 into 5% ortophosphoric acid - for 4 kV better to use about 1...2 cm, especially whilst not hardened well. Epoxides - any epoxide resin is more than good, however as lighter color as better voltage - up to 50 kV/cm or 5 kV/mm. The silicone rubbers including acetic tubes - second sort insulators but 1 kV/mm may be appropriate. Stirolic household glue-tubes (like liquid nails or instant mount etc) even better than acetic. Just the furniture lack, nitrolack, epoxy lack etc - very well up to 1 kV/mm or epoxy severe more. Just there is no restriction of any known insulation materials for Your case. Yes, and natural pitch is included however it is bit dirty material.
 

Thread Starter

mohan.n2293

Joined Jan 23, 2017
60
For 4 kV is every kind of insulation materials available, its not a 50 kV where only few good alternatives exist.
One is floor linoleum, those white colour elastic with no threads or textile inside. It stand at 2,5 mm thick about 40 kV. Other is teflon, even more strong. The ebonit (hard rubber) and getinax (paper in fenolic resin) - at least 8...10 kV is realistic for them. The PPE, PET, plexyglass, polystirol - good up to 10 kV, but last not likes the frequeancy over 30 MHz. Glass, quartz, ceramics - very strong and good, but difficult to form, need a diamond ring or torch. Powders like white-clay or silicon sand or MgO or AlO2 into 5% ortophosphoric acid - for 4 kV better to use about 1...2 cm, especially whilst not hardened well. Epoxides - any epoxide resin is more than good, however as lighter color as better voltage - up to 50 kV/cm or 5 kV/mm. The silicone rubbers including acetic tubes - second sort insulators but 1 kV/mm may be appropriate. Stirolic household glue-tubes (like liquid nails or instant mount etc) even better than acetic. Just the furniture lack, nitrolack, epoxy lack etc - very well up to 1 kV/mm or epoxy severe more. Just there is no restriction of any known insulation materials for Your case. Yes, and natural pitch is included however it is bit dirty material.

Thanks for your replay ,

Please can you check attached bobbin pin's can withstand isolation of 4kv
 

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Thread Starter

mohan.n2293

Joined Jan 23, 2017
60
Are you designing to any particular standard? If so, you should use the creepage distance.

There is a table on page 4 of this document that might be of some use to you unless you need to design to a different standard.

www.cui.com/catalog/resource/iec-60601-1-medical-design-standards.pdf

View attachment 135781

You can check the bobbin specification to see whether your creepage distance is greater than 8 mm for points 4 KV apart.
Thank for your reply sir,
But when i go through this attached documents im seeing that 3mm gap will be enough to give 4kv isolation please see page number 18
 

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DickCappels

Joined Aug 21, 2008
6,640
The highest page number I can see is page 14.

After another look at the bobbin datasheet, I do not see any voltage raging or creepage distances. 4 KV is a high enough voltage that you should be concerned about corona which can eat away at insulation, thus you should use 10 KV wire. If I were doing this I would probably use a piece of high voltage for the output lead instead of using a pin.

If you have not considered it already, you need to make sure the winding inside the transformer does not arc internally. Using appropriate insulating tape between layers, limiting the voltage between layers, and as the voltage goes up, leave more and more creapage distance between the winding and the edge of the tape, so the highest voltage layer has fewer turns than the lower voltage layer.

If only one end of that winding has high voltage on it, you can bring out the low voltage end of the coil on a pin, but it is best to bring out the high voltage on a separate high voltage wire.

The transformer should be potted or at the very least vacuum impregnated with a suitable varnish to prevent deterioration of the insulation on the wire.
 
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