Superimposed pulse ignitors are the most reliable method of starting High Pressure Sodium and Metal Halide lamps operating in wire wound ballast circuits. The lamp arc is struck by applying a number of high voltage pulses, which are superimposed on the lamp voltage waveform. Unlike impulser type or parallel ignitors, the superimposed pulse ignitor generates the high voltage pulses within the ignitor itself. The ballast is not subjected to the high voltage; no ballast tapping is required, and long term circuit reliability is greatly enhanced. The determining factors for successful lamp ignition are pulse height, width, phasing, distance between pulses, and number of pulses per cycle. For cold lamps a pulse height of between 1 and 5kV is required, depending on lamp type. Once the lamp is hot, the standard ignitor will not be able to re-strike the lamp until the arc tube has cooled. Re-strike time is typically in the range of 30 to 60 seconds for High Pressure Sodium (SON) lamps, and 5 to 15 minutes for Metal Halide lamps. LIL ignitors, in standard or timer versions, are available for lamp ratings from 35W to 2000W on voltage supplies of between 110 and 415 Vac at 50 to 60 Hertz.

Ignitor Selection

Lamp manufacturers data will specify the required conditions for ignition. However, for commonly available lamps, the mains voltage and wattage are the only factors normally required to enable correct ignitor selection. (See Lamp Data Section). Most SON and Metal Halide lamps require an external ignitor. However, there are some lamps that include built in starters and some that operate only with special electronic power units.

Lampholders must be rated for use at the specified ignitor pulse voltage. Hot restrike ignitors, with pulse heights of greater than 5kV, can only be used with double ended TS or D2 lamps.

Timer Ignitors

The use of timer type ignitors is recommended for additional safety. LIL S.I.P. ignitors are available with digital timer cut-out control, set to 2, 12 or 15 minutes


Ballasts are not subjected to very high voltages when used in superimposed ignitor circuits and, therefore, all normally available ballasts are suitable. The ignitor taps provided on some ballasts are not required, and should not be used in conjunction with superimposed pulse type ignitors.

Ballast Thermal Protection

Use of a ballast equipped with a thermal safety cut-out is recommended for additional safety.

Response and Cut-out Voltage

These are the voltages at which the ignitor respectively starts to operate and ceases to operate, and are measured without a lamp in circuit. A low response voltage enables the ignitor to operate under poor mains supply conditions. A high cut-out voltage ensures that the ignitor stops pulsing after the lamp has struck.

Pulse Voltage

The quoted maximum pulse voltage applies only if the load capacitance is within the limits stated. The value given is the highest peak voltage achieved by any one or more pulses in any sequence.


Load capacitance should be kept to a minimum by positioning the ignitor as close as possible to the lampholder. The maximum cable length depends on cable capacitance but the total capacitance must not exceed the quoted value, under any circumstances. Some typical values for the capacitance of PVC insulated cables (1.0 to 4.0mm2) are as follows :

1. Unsheathed single cores, loose packed in earthed conduit 70pF/m

2. Unsheathed single cores, tight packed in earthed conduit 120pF/m

3. Twin and Earth (Flat section) 115pF/m

4. Twin SWA/Multicore SWA/Unarmoured Multicore 300pF/m

During lamp running the lamp current, passing through the ignitor windings, will generate an internal heat rise in the ignitor. The value of the limiting temperature, as stated on the casing, should not be exceeded and the ignitor should be located in the coolest possible position, within the limits permitted by load capacitance considerations. Standard LIL Ignitors are intended for installation within a luminaire or suitable enclosure. For special applications contact our technical team.


High voltage cables must be suitably rated and insulated. All terminals must be tightened securely and firmly. Circuits must only be wired strictly in accordance with the wiring diagrams and the restrictions given herein.

Quality & Compliance

LIL Ignitors are produced under strict quality controls. Certificates of Conformity are available upon request. LIL ignitors are designed to comply with the requirements of EN60926 and the relevant European safety directives.

Lamp Ignition Ltd. 41 Vanalloys, Stoke Row. Oxon. United Kingdom. RG9 5QW Tel:+44(0)1491-680444 Fax+44(0)1491680444 e.mail: