Isolation

Discussion in 'General Electronics Chat' started by bte, Feb 7, 2013.

  1. bte

    Thread Starter New Member

    Aug 15, 2012
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    0
    I have a circuit below, both coils are located very close to each other (wrapped ontop of one another). The DC-DC converter is isolated from the input to the output. The insulation on the coil wires cannot block 4kv, will this damage the battery or apply a large voltage to this circuit or will the isolation provided by the DC-DC converter protect the low voltage side?

    Could I use a diode string to protect the low voltage side? What can I do to ensure the 4kv doesn't feed back to the low voltage side?

    The circuit is simplified.

    Thanks for any advice.
     
  2. #12

    Expert

    Nov 30, 2010
    16,269
    6,782
    First, read the specifications on the DC converter. They will tell you its isolation voltage. I used one for a 5 volt filament on a rectifier tube with 400 volts DC and it worked because it was designed to work that way. 4000 volts is not likely to be survived by a DC to DC converter.

    Then your coils, close together and not built to withstand 4000 volts. No amount of diodes will fix that. You are in for trouble. Change your design!
     
  3. bte

    Thread Starter New Member

    Aug 15, 2012
    8
    0
    The DC-DC converter is a standalone package that takes 0-15vDC and outputs 0-4kv DC. I can't change that, the voltage must be 3-4kv and the coils must be located closely.

    From the DC-DC converter datasheet:

    ELECTRICAL SPECIFICATIONS*3 SEE SHEET 2
    INPUT VOLTAGE: See Table FOR
    INPUT CURRENT*1: (NO LOAD) < 500mA MECHANICAL
    DETAILS
    (FULL LOAD) <1.5A
    TYPICAL TURN-ON VOLTAGE: 0.7 Volts
    ISOLATION: 3,500 Volts + Vout
     
  4. #12

    Expert

    Nov 30, 2010
    16,269
    6,782
    Good. You confirmed that the DC to DC converter will survive.
    Now, all you have to do is design coils that can be close to each other and survive 4000 volts. I have some spools of 5000 volt test lead wire so I am sure you can buy the wire that will survive. Look for wire with 5000 volt insulation.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    You might want to try to wrap some kapton tape between the windings.

    However, the output side has 4KV across it, so unless you wrap it in a single layer it could short to itself.
     
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