Control gear for fluorescent lamps

Discharge lamps have to be operated with control gear to limit the current. There is a choice of conventional, low-loss or electronic control gear. An important factor as far as quality is concerned is their power loss which, together with the lamp wattage, is used to calculate the system wattage.Electronic control gear (ECG) In contrast to conventional control gear, ECGs operate at frequencies at or above 30 kHz which means they offer significant gains in efficiency. These gains are based essentially on two mechanisms:
A reduction in electrode losses.
An increase in luminous efficacy, which is due almost entirely to more efficient conversion of electrical energy into the UV lines of the mercury atom at 185 nm and 254 nm.The use of modern ECGs, above all for fluorescent lamps, has led to significant increases in lighting comfort, economy and reliability.
Lighting comfort
Flicker-free starting
Pleasant flicker-free light with no stroboscopic effects
Silent operation with no annoying hum from chokes
No flashing of faulty lamps
Automatic restart of replacement lamps
Economy
Up to 30% savings in power input compared with CCG operation
More than 50% longer lamp life compared with CCG/LLG thanks to preheat start
Low maintenance costs
Suitable for use in emergency lighting systems to VDE 0108
Reduction in energy costs for air-conditioning systems
Reliability
Safe shutdown of defective lamps
Compliance with the specific standards for safety and EMC
Protective circuit to guard against transient voltage surges and prolonged overvoltages
Dimmable electronic control gear enables compact fluorescent lamps to be dimmed smoothly and without flicker from 100% to 3% luminous flux and tubular fluorescent lamps from 100 % to 1% luminous flux. Control is via a separate 1-10 V interface or a digital addressable lighting interface (DALI).
Conventional control gear (CCG):
This is a simple self-inductance comprising an iron core around which copper wire is wound. Because of its ohmic resistance there is considerable power losses and from self heating. The system wattage for a 26W compact fluorescent lamp operated with conventional control gear is 32 W; in other words, the power loss is 6 W (23%). By contrast, the system wattage with an ECG is 28 W, which corresponds to a power loss of only 7.5%. The various operating modes are as follows:
Switch-start operation
Starter less operation
Control gear with temperature limitation
Switch-start operation can be described as follows:
The voltage needed for the starter to generate a glow discharge between the bimetallic contacts, is lower than the ignition voltage of the lamp with cold cathodes. When mains voltage is applied, the starter generates a glow discharge, the current of which heats up the cathodes. The bimetallic contacts then close and the full short-circuit current of the choke flows through the cathodes of the lamp. As the bimetallic contacts cool down they spring open again. A high voltage pulse is generated by the choke to ignite the lamp. Once the lamp has ignited only the lamp voltage is across the starter. This voltage is too low to cause the starter to initiate a glow discharge, so does not attempt to light the lamp.Special lamps are needed for starter-less operation. Whereas fluorescent lamps connected to a European 230-240 V mains can be operated with simple chokes and an additional preheating transformer or a sophisticated double resonance choke is needed for starter-less operation. The voltage for lamps connected to American 120 V supply systems has to be transformed with two additional heater windings on the control transformer, which involves little extra outlay. For this reason, starter-less circuits are widespread in the USA. Control gear with temperature limitation help ensure that dangerous overheating does not occur as lamps reach the end of their lives. This protection is provided by thermal cut-outs approved in VDE 0712 T10 The European Ballast Directive (2000/55/EC) has classified all fluorescent ballasts in terms of their energy efficiency. The most inefficient types will be legally banned from sale in Europe from May 2002. The aim of the Directive is to encourage the widespread use of electronic control gear which are the best in terms of energy efficiency. Low-loss gear (LLG): Compared to conventional control gear, low-loss gear has a lower power loss but are larger and are more costly to manufacture because of their improved design and larger iron cores. The system wattage for a 26 W compact fluorescent lamp, for example, is around 30 W