Investigation of the Series Inductance Value of Step-Up Transformers for HID Lamps Igniters

Among the two main possibilities of connecting electronic igniters (series and parallel connection), the series one is widely used. In steady state operation, the series igniter should behave like a short circuit, in order not to affect the operation of the lamp-ballast system. The main disadvantage of this configuration is the high value of the secondary winding of the step-up transformer used for providing the high voltage pulses to the lamp. In this paper, an investigation of the influence of the series inductance of the secondary versus the capability of igniting the lamp is carried out. Firstly, the characteristics of the starting pulses for a 35W MH lamp are fixed, accordingly the technical literature and the standards found (in this first approach, no hot re-starting of the lamp will be considered). Later, a design of an igniter based in an E30 E-core is done. From this basic design, some characteristics of the ignition are found (pulse width, non-saturation, etc.). After that, the proposed modifications are shown, in order to maintain the ignition capability of the transformer lowering the series inductance of its secondary winding. Conclusions show how the series inductance can be made as low as 100muH for a transformer in an igniter for 35 metal halide (MH) lamps. Several igniters have been built and tested upon 10 35W MH lamps, in order to verify the obtained results