step down transformer

Discussion in 'The Projects Forum' started by wasanne, Dec 25, 2008.

  1. wasanne

    Thread Starter New Member

    Dec 22, 2008
    is it possible to build a cheap step down transformer that will accept a car ignition coil as the source power and privide a high amp output. I can't measure the voltage or amperage from a coil but I believe the volts to be at least 30,000 but the amps are only milliamps. Stepping down voltage must increase amps but how far can you step down the voltage and what possible amperage could be extracted from it. thanks. wasanne.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Transformers are devices that deliver power, but at different voltage and current.

    Let's say an ignition coil still has the same input as ones I am familiar with. The primary is driven with 12 volts and 7 amps, or 84 watts of power. Going the other way, the power it can handle stays the same. So driving the secondary with a high voltage pulse will still only be able to transfer 84 watts to the primary.

    There are better transformers for high current applications. How high is the current you wish to use, and at what voltage?
  3. SgtWookie


    Jul 17, 2007
    Well-designed transformers are fairly efficient, but you'll always lose some power when you exchange voltage for current (or vice versa), due to the resistance of the windings, eddy currents, and other losses.

    So, when you step up the voltage using an ignition coil, some of the power is lost in the form of heat due to the resistance of the windings. If you then use another transformer to step the voltage back down to increase current, you incur another loss due to the resistance of the windings. You wind up with less effective power than what you started off with.

    These losses are acceptable for long distance power transmission; your power company uses this very scheme for power distribution. High voltage at low current requires far smaller sized conductors than high current at low voltage.

    If you really wanted more current at a lower voltage, you would be better off to start with a step-down transformer to begin with.

    What is it that you're considering?