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I'm building a 40KV hv transformer very low power, is going to have 16,000 turns on the secondary, and is going to be in oil, after how many turns should I consider insulation between each layer and what would be a good material? I'm planing to use 38AWG wire, and the inner diameter of the core is approximate 20mm
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
This will depend on the aspect ratio of a cross-section of the winding.
The potential difference between any two adjacent wires in the winding must not exceed the breakdown voltage of the enamel insulation specified by the wire manufacturer, and, in practice, must be a lot less than that - perhaps one third of the RMS voltage, so that the winding will be able to resist voltage transients, and of course, back EMF due to the collapse of the magnetic field in the inductor.
Kraft paper is the most common insulation used in oil-filled high voltage transformers, but great care must be taken to ensure that the paper is saturated in the dielectric oil, and that there are no voids where arcing and consequent breakdown could occur. Vacuum impregnation is the usual means for achieving this.
Registered Member #3700
Joined: Sat Feb 19 2011, 12:59PM
Location:
Posts: 107
Andre :
Anyway, please provide a sketch of the core with dimensions, and:
Operating frequency, [Hz]
Primary voltage [V], primary number of turns, Np
Desired insulation between the beginning of secondary and primary [kV], desired insulation between the beginning of secondary and the core. [kV]
Them we may figure out the insulation bewtween prim and secondary, insul. between secondary and core. as well as the insul between layers, in milimeters
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276
i would think, if you can, try to do a -20Kv-0-+20Kv output, then you have less to insulate and still get 40Kv across both of them, depends on your project however i guess.
thanks but I'm doing +40KV and -40KV, I'm doing insulation in every layer of the secondary, I did some research and that what people are doing. I'm operating at 40Khz the size of the core is about 20 mm diameter
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
That's not going to work. A 16000 turn coil will have a very low resonance frequency, way below 40kHz, so most of your drive voltage will end up across the leakage inductance.
so what would be the correct way to do it? I'm trying to achieve a transformer with lowest inductance leakage possible, I will like to have a rectangular pulse shape with a fast raise, I been reading this design guide, eventually I will like the pulse to be 30hz also what would be the best copper wire to use?(type on insulation) so I will have minimum to no insualtion between layers.
well Wolfram it been 48 hours of silence, since you havent reponded I'm going to tell you the answer, if is an 100 layer coil it does not matter if you start insulation from a layer 25 or 50 or 75, it would be the same as not putting insulation at all, because at 40000 KV you would have about 400V in each layer, so as __=|(:3)-|--{__ said best way to separate in 2 diferent transformer or put the insulation in every layers, if you think I'm wrong you can prove me with science(formulas) not philosophy.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
Just to be sure, when you say 30 Hz do you mean one short square pulse every 1/30th of a second ... or do you mean a near square wave at 30 Hz? (Pretty sure you can't get close to that with the size of transformer you want.)
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after how many turn on a HV transfomer you start insulation
