Help bypassing over current protection circuit.

Discussion in 'The Projects Forum' started by chrisblack604, Jan 14, 2016.

  1. chrisblack604

    Thread Starter New Member

    Dec 31, 2015
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    I have a 12v DC Fan made by SPAL. It is rated @ 40amps. The fan is used in cooling a radiator on my engine dyno. The fan cycles on and off about once per minute for 10 minutes at a time.

    It is currently drawing power from a car battery which is connected to a 2.5 amp battery tender. I wanted to eliminate the battery and tender and use a AC to DC power supply. So I bought the venom ps600 40 amp power supply.

    The problem is that the power supply goes into protection mode as soon as the fan turns on. Turns out the ps600 has an over current protection circuit.

    Can someone explain what I need to do to either bypass the protection circuit or reduce the inrush current of the fan?

    Thanks
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Last edited: Jan 14, 2016
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    If you bypass the current sense, you risk blowing up the psu, better to use inrush resistors.
     
  4. chrisblack604

    Thread Starter New Member

    Dec 31, 2015
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    would I need a 40amp resistor?
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Click the "View training module" in the first link in post #2 for guidance on NTC selection. It's directed at capacitive applications, but much of it would apply to other apps. You might want to consider bypassing the NTC (as mentioned in that module) after the inrush has occurred.
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    No, resistors are measured in Ohms not Amps.

    Can you measure the current when connected to the battery, when its running?
     
    Last edited: Jan 15, 2016
  7. #12

    Expert

    Nov 30, 2010
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    Your ignorance about the starting current of electric motors has led you to eliminate a perfectly good power supply and buy the wrong size of power supply. I recommend you get your money back and use the supply that works.
     
  8. chrisblack604

    Thread Starter New Member

    Dec 31, 2015
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    #12
    how can I determine the starting current? And how do I determine I am buying a supply that works?

    Dodgydave
    I understand that the resistors are typically measured in ohms. The ntc inrush current resistors on the website listed above are rated in amps. I still need to watch the videos to understand more about them.
    I don't have anything to measure the amperage when the fan is running. What do I need to buy?
     
  9. #12

    Expert

    Nov 30, 2010
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    Electric motors need seven to ten times their run current to start. If there is a label for Locked Rotor Amps, that is the start surge. This 10X current requirement makes buying an electronic supply a Pain In the Butt because you end up paying for 90% of what you aren't using.:mad:.
     
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