The effect of active antennas on the hot-restrike of high intensity discharge lamps
Thomas Höbing, Andre Bergner, Bernd Koch, Freddy Manders, Cornelia Ruhrmann, Jürgen Mentel, Peter Awakowicz
JOURNAL OF PHYSICS D-APPLIED PHYSICS, Volume: 47, Issue: 20, Article Number: 205501, DOI: 10.1088/0022-3727/47/20/205501, Published: MAY 21 2014
The ignition voltage of high intensity discharge (HID) lamps with mercury as the buffer gas may rise from 3 kV for the cold state up to more than 15 kV for a hot lamp. By coating a lamp burner with an electrically conductive layer, which operates as an active antenna, the ignition voltage of HID lamps can be significantly reduced. An active antenna connected to one of the lamp electrodes transports the potential from this electrode to the vicinity of the opposite electrode and generates an enhanced electric field inside the burner. On applying a symmetrically shaped ignition pulse, a weak pre-discharge within the first half-cycle produces free charge carriers initiating ignition of the lamp within the subsequent second half-cycle. The authors present a set-up for electrical and optical investigations of hot-restrike in HID lamps. The ignition voltage is measured for two different polarities as a function of the cooldown time. An analysis of its reduction is given. Furthermore, the pre-discharge is investigated by means of short-time photography. It is demonstrated that a negative polarity of the active antenna within the first half-cycle and a positive polarity within the second one is the most effective succession.