Loading ...
Sorry, an error occurred while loading the content.
 

Re: Headlight operates on AC

Expand Messages
  • Keith Simmonds
    ... it pulses bright/dim at idle speed? It only gets current half the time? Must be. ... Mike, following your letter, I just came back to the group to see
    Message 1 of 10 , Apr 1, 2006
      --- In royalenfield@yahoogroups.com, michaelszoke@... wrote:
      >
      > Interesting that the headlamp operates on AC current. Is that why
      it pulses bright/dim at idle speed? It only gets current half the
      time? Must be.
      >

      Mike, following your letter, I just came back to the group to see what
      the conversation was about.
      As far as a lamp bulb (standard, quartz, halogen, whatever) is
      concerned, ac/dc makes no difference, it's power (volts x amps =
      watts) which matters.

      AC supply (mains or motorbike) is delivered as a sinewave, where (for
      a given power requirement) the actual peak voltage and current
      delivered is slightly higher that the DC current and voltage which
      would be supplied. *BUT* the *effective* AC voltage and current is
      0.707 of the peak value. This is known as the r.m.s. (root mean
      square) value of an AC supply and is the direct equivalent of the DC
      which would be supplied. RMS is defined as the value of an AC supply
      which will produce the same amount of heat in an electrical load as
      that of a DC supply.

      The bright/dim pulsing is nothing to do with it only getting current
      for half the time (it doesn't). It is because the AC sinewave is only
      being produced very slowly, which gives the lampbulb time to cool down
      (dim) before the next sinewave peak comes along.
      The lampbulb will produce light on both positive and negative parts of
      the AC waveform, but it takes a finite time for the AC current &
      voltage to reach a sufficiently high level to heat (light) the lampbulb.
      Also, the fact that the alternator is turning slowly means that the
      power output from the alternator is reduced from that produced when it
      is turning quickly, so the lampbulb never reaches quite the brightness
      it does at higher revs.

      Hope that clears up any confusion

      KeithS
    Your message has been successfully submitted and would be delivered to recipients shortly.