The Active Reactor

The Device

The device consists of an electronic control unit which controls an HID lamp in a pre programmed manner. The mode of operation of the device is variable power, constant light, as opposed to a conventional ballast which operates predominantly at constant power, variable light. These two different modes of operation greatly affect lamp energy consumption and lamp performance.

The device also controls a pre programmed lamp start up sequence for optimum lamp starting.

Because the device uses feedback in its operation and control strategy, the lamp it is immune, to a very large extent, to lamp disturbances such as variations in supply voltage and lamp temperature variations.

Figure 1.

Variable Lamp Power Operation

The Active Reactor varies the power to the lamp, starting with a low power for a new lamp and gradually increasing the power with lamp age to full power for an old lamp.



	Energy Saving


	Metal Halide Lamps	15-20% in energy saving

	High Pressure Sodium Lamps	20-25% in energy saving

Lamp life extension

Because lamps controlled by the Active Reactor run all their life below their rated power, the mechanisms which reduce lamp life and lumen maintenance are inhibited to a significant extent. These mechanisms are (in simplified form):

Running a lamp at lower power means the lamp runs at a lower thermal loading and consequently diffusion of the amalgam through the arc tube is reduced; moreover, chemical reactions within the arc tube (between the amalgam and the arc tube and the electrodes) are also reduced. Amalgam diffusion and reactions within the arc tube are the chief causes of lamp ageing.

Running the lamp at lower power also means the lamp (and electrode) current is lower and therefore the electrodes are not “burnt” to the same extent. Burnt electrodes (particularly from overheated lamps) are a major cause of lamp failure.

The Active Reactor also has a preset starting current during lamp ignition. This current is such that the glow to arc phase time is minimised which reduces electrode sputtering during lamp starting.

The above detrimental effects on lamp life and lumen maintenance are negated to a significant extent by the Active Reactor. Field and laboratory trials have indicated that increase in lamp useful life is typically


Metal Halide Lamps	greater than 25% increase

High Pressure Sodium Lamps	greater than 50% increase

Circuit and Operation

Circuit Diagram

The PCB is shown in figure 1 (above) and a schematic wiring diagram of the Active Reactor is shown in figure 2 (below). The following describes the operation of the circuit:

The Active Reactor is connected into the circuit be removing the standard reactor ballast and replacing it with the Active Reactor components. The power factor capacitor and ignitor remain in the circuit.

The Active Reactor components are:

a	the Active Reactor printed circuit board which contains the electronics to control the lamp power and lamp starting.
b	a Main Ballast which supplies approx 75% of the lamp power. For example, for a 400 watt HPS lamp this power is 300 watt.
c	a Current Injector (Control Ballast) which supplies approx 25% of the lamp power. For example, for a 400 watt HPS lamp this power is 100 watt.


	Active Reactor Legend


	MB		Main Ballast
	CB		Control Ballast (Current Injector)
	SW		Electronically Program Controlled Triac Switch
	PCB		Active Reactor Printed Circuit Board


	*Figure 2.*

Operation

The Active Reactor utilises the main ballast as the primary source of power for the lamp and injects additional current (and power) into the circuit via the control ballast to achieve the required lamp operating conditions.

The minimum power the lamp can run at is typically 75% rated power when the control ballast is turned off completely. The maximum power the lamp can run at is typically 100% rated power when the control ballast is turned on fully. Hence the lamp can run at any instant, at any point in its life, between 75% and 100% power by appropriate current injection into the lamp.

This operation is summarised below:



Main ballast	Control ballast	Lamp power


ON	fully OFF	75%


ON	fully ON	100%


ON	partially ON/OFF	75 -100%

The 25% variable power which can be delivered to the lamp is just enough to offset the 30% flux depreciation during the life of a lamp.

Operating Characteristics

If the Active Reactor electronics fails then the lamp runs only on the main ballast at 75% rated power for the remainder of its life.

On a new lamp the control ballast is substantially turned off while on an old lamp the control ballast is substantially turned on.

The Active Reactor can operate to specification for input voltage variations of +/- 10%. Above these voltage variations it will still operate but will not regulate the power to the specified value.

The Active Reactor monitors the supply voltage, ballast voltage, lamp voltage and lamp current to control the lamp power.

The Active Reactor uses the lamp voltage as the basis for determining lamp life. Typically the following values are used:



	MH lamp	HPS lamp


New Lamp	130V	90V


Old lamp	160V	170V

Thus if a lamp fails and is replaced by a new lamp it will automatically be adjusted in power to run at the same light output as it did before it failed, that is, at the same light output as all the other lamps in the installation.

The ballast losses of the Active Reactor compared to the losses of a standard reactor ballast are summarised below:



	Active Reactor	Standard ballast


New Lamp	80%	100%


Old lamp	105%	100%

Overall, throughout the life of a lamp the Active Reactor ballast losses are lower than the standard reactor losses.

Comparison with Electronic Ballast



		Mode of Operation


		Active Reactor	Operates by delivering variable power to a lamp resulting in constant light output Power is “ramped up” from a low value for a new lamp to full power for an old lamp


		Electronic Ballast	Operates by delivering constant power to a lamp resulting in variable light output Full power is applied to a lamp for all its life



		Energy Savings


		Active Reactor	Results in substantial energy savings by using variable power strategy Typically 20-25% savings for HPS lighting and 15-20% for MH lighting


		Electronic Ballast	Results in some energy savings by using electronic ballast over standard magnetic ballast Typically 5-8% for HPS and MH lighting



		Lamp Life Extension


		Active Reactor	Results in significant lamp life increase by “under-driving”a lamp for all its life Typically >50% increase in life for HPS lamps and >25% increase in life for MH lamps


		Electronic Ballast	Results in some lamp life increase over standardmagnetic ballast Typically 20% increase for MH lamps. No figures available for HPS lamps



		Failure Mode


		Active Reactor	If electronics fails lamp keep burning at lower power typically at 70% rated power


		Electronic Ballast	If electronics fails lamp extinguishes



		Lamp Types and Powers


		Active Reactor	Can be used on both HPS and MH lamps in the power range 150 watt – 2000 watt


		Electronic Ballast	Predominantly used on MH lamps in the power range 150 watt – 450 watt



		Size


		Active Reactor	Relatively compact size. Electronics hermitically sealed in IP66 metal cassette


		Electronic Ballast	Size is larger for low power lamps and very large for high power lamps



		Cost


		Active Reactor	Relatively low cost device over full range of lamp powers


		Electronic Ballast	High cost of device for low power lamps and very high cost for high power lamps



		Abbreviations


		Active Reactor	High Intensity Discharge (A term generally associated with high power 150 watt and above HPS and MH lamps)


		Electronic Ballast	High Pressure Sodium (A “yellow” light predominantly used in streetlighting)


		MH	Metal Halide (A “white” light predominantly used in industrial and sports lighting)

Comparison Table




Parameter	Active Reactor	HID Electronic Ballast



Lamp Types	Metal halide and high pressure sodium	Predominantly metal halide



Lamp Powers	150 – 2000 Watt	150 – 450 Watt



Lamp Frequency	50/60Hz (standard power frequencies)	100kZ (high frequency type) 120Hz (low frequency type)



Operating Strategy	Variable power-constant light Typically 70%-80% rated power at start of lamp life ramping up to 100% power at end of life	Constant power-variable light 100% of rated power throughout lamp life



Ballast Housing	Remote for higher wattages Integral for lower wattages	Remote for higher wattages Integral for lower wattages



Energy Savings	Metal halide : 15-20% energy savings High pressure sodium : 20-25% energy savings	Metal halide : Typically 5-8% High pressure sodium : Figures not available.



Lamp Life	Metal halide : Typ >25% increase High pressure sodium : Typ >50% increase	Metal halide : Typ 20% increase High pressure sodium : Figures not available.



Lumen Depreciation	Metal halide : Typ 15% improvement High pressure sodium : Typ 25% improvement	Metal halide : Typ 10% improvement High pressure sodium : Figures not available



Failure Modes	If electronics fails lamp keeps burning. Lamp operates through main ballast at 70% power.	If electronics fail lamp extinguishes



Costs	Low cost Similar cost for all lamp wattages	High cost Very high cost for higher wattage

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