7.2 Influence of ambient temperature on ballasts and luminaires. Osram HQI-E 150 W/NDL CL
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7.2 Influence of ambient temperature on ballasts and luminaires
As the ambient temperature increases, the temperature of the luminaire components also increases at the same rate. The lamp reacts to a higher ambient temperature with an increase in lamp voltage and lamp wattage. This can accelerate corrosion and aging processes. An increased re-ignition peak can result in failure by the lamp going off at an earlier point in the service life.
Temperature and ignition voltage are critical, because the effects of exceeding the limit values are often only detected after a longer period of time.
This results in a sudden, not gradual, decrease in service life.
Please note that lamps vary in wattage (permitted up to +12%) and temperature, and that according to IEC 60926, ignition units may generate output voltages of up to 30% above the nominal value.
Higher temperatures at choke and ignition unit mean a reduced service life for these parts or also earlier failures. The limit temperatures for chokes is generally
130 °C, and 70 °C to 105 °C for ignition units (consider manufacturer’s instructions). A higher ambient temperature means that luminaires are increasingly switched off, triggered by the thermal protection.
It can therefore be assumed that the high ambient temperature has a distinctly negative influence on the service life of lamps and luminaires.
Luminaire design has a great influence on the temperature of the parts. Heat-generating parts such as chokes and filter coils can be mounted on materials with good heat conducting properties and adequate ventilation openings to ensure there is ample heat dissipation. The greatest possible spacing should be kept between heat-sensitive parts such as ignition unit and capacitors, and heat-generating parts. If necessary, forced cooling should be provided by ventilation elements.
At the end of the lamp service life, far higher temperatures than normal can occur in the pinch area caused by outer bulb discharges (see also chapter 6.2 “Failure mechanisms of metal halide lamps”). The socket in the immediate vicinity of this point must be rated for that temperature.
• Ignition voltages:
The socket must be rated for the corresponding ignition voltage.
When mounting the socket and the supply leads in the luminaire, it is important to consider the required creepage distance and clearance, as well as distances in the insulation. The luminaire IEC
60598-1 standard corresponding to EN 60598-1 defines the safety requirements for ignition voltage regarding creepage and clearance distances.
Particularly when using high-pressure discharge lamps with Edison bases E27 and E40, care is required to ensure that the sockets are approved for discharge lamps. Suitable sockets are marked with the value to max. “5 kV” and comply with the increased creepage and clearance distances required in the socket standards IEC 60238 or
EN 60238 (VDE 0616 Part 1). In the same way, the other base systems are subject to the socket standards for special sockets IEC 60838-1 or
EN 60838-1 (VDE 0616 Part 5).
CAUTION : Do not use sockets for incandescent lamps, e.g. E27 or R7s. Sockets for discharge lamps must be used to handle corresponding ignition voltage.
7.3 Lamp holder
Metal halide and high-pressure sodium lamps have many different bases. These include for example RX7s,
Fc2, G8.5, GX10, GX8.5, GU6.5, G12, G22, GY22, E27,
E40 and K12s, depending on whether the lamps are single- or double-ended. All sockets must be rated for the typical conditions for discharge lamps, i.e. high ignition voltage and high temperatures. It is up to the user to make an appropriate selection and to ensure that the lamp holders are installed correctly according to the corresponding regulations (e.g. IEC 60598 / VDE
0711, IEC 60335 / VDE 0700). Sockets consist of several parts, each with their own function limits. Exceeding these limits causes premature failure of the sockets.
• Temperature code Txxx (continuous use temperature)
This is the highest temperature for which the socket was designed. The temperature of special holders is measured at the socket contact according to 60838-1 (all holders for high-pressure discharge lamps except Edison sockets). If the heat resistance of insulation, terminals and leads deviate from this temperature limit, then separate limit values are stated. In the case of Edison sockets (according to IEC 60238 ), the rated temperature is valid for every point in and on the socket.
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