UV Lamp Ballasts
Additive Ballasts Controlled
|Mercury Vapor Ballasts
vapor ballasts are
designed to drive tubular medium pressure ultraviolet lamps.
There are two types of mercury vapor lamps. The most common
is the medium pressure lamp with no metal additives. This
lamp is available in arc lengths of 1 to 120 inches. The
other type of lamp is a metal-additive-mercury-vapor lamp.
The additives used in the lamp create changes in the lamps
spectral output enhancing different portions of the ultraviolet
spectrum. The ballast initiates and controls the arc in
mercury and metal additive curing lamp. This is accomplished
by providing an instantaneous high voltage to strike the elements within a mercury vapor lamp, creating a plasma that, once initiated, is sustained by the ballast. Total wattages up to 50 kilowatts can be designed. Our constant wattage ballast consists of a transformer, capacitors and igniter.
The advantage of a constant-wattage ballast is that it allows for wide variations in input voltage to affect output wattage by only a few percent.
These ranges can be customized to meet your applications requirements. Typical designs have an output variation of only +/- 3% with an input voltage varying over a range of -15% to +10%. Constant wattage is accomplished by a resonant tank circuit in which the lamp winding is in controlled magnetic saturation with the AC capacitors, such that voltage swings on the input side have a very small impact on lamp current. An interesting feature is that these current-limiting capacitors can be switched (see schematic) in and out of the circuit to provide various lamp power levels.
additive ballast is required for metal additive lamps.
In addition to needing a higher open circuit voltage
a metal-additive lamp requires a special wave-shape
to main the arc plasma. The metals inside the lamp
create electrical noise in the ballast secondary
circuit, which normally would cause the lamp to extinguish
during lamp warm-up, if a standard ballast were used. The
metal additive ballast uses a special bridge gap
design to successfully shape the waveform and absorb
From the user
standpoint the metal-additive ballast has the same
schematic as the mercury ballast. And can be used
to operate a mercury lamp, but a mercury lamp ballast
can not be used for an additive lamp.
Ballasts are available
in sizes from 400 watts to 50kW in 50, 60, or 50/60Hz.
Typically, input power factor is better than ninety
(90%) percent at nominal input voltage. Ballasts
are constructed using silicon grain oriented steel,
UL rated copper wire, UL Class H insulation system
and impregnated with a unique epoxy varnish for maximum
ballast offers a linear variation of output power
from 40 to 100%. A standard ballast switches capacitors
in and out of the circuit to change lamp power as
a step function.
With a Controlled-Ballast,
lamp power is adjusted by varying the conduction
time on an inductor, which negates capacitance in
the circuit allowing enhanced control of lamp current.
Lamp current is sensed in a closed feedback loop
circuit that can instantaneously respond to changes
making the necessary adjustments.
is that since the controls are on the secondary of
the ballast all the electronics are protected from
power problems found on the primary side. A PLC interface
is available to communicate with the ballast in order
to vary lamp output. In order to protect all of the
control circuitry from power problems typically found
on the primary the control circuits are all located
on the secondary of the ballast.
- Continuously variable output power
from 40% power through 100% power
- Precise regulation, less than a
2% change in output power over an input range of
+l0% to - 20%.
- Low input current distortion seen
on SCR controlled designs.
- No need for mercury relays.
- Very high input power factor. Typically
better than 0.90
- Low lamp current crest factor, 1.5
- High watt efficiency
- Controllable via a Programmable
Logic Controller (PLC). A 4ma to 2Oma signal is preferred
with 0 to 5 volt or 0 to 10 volt option.
- All components are pre-wired and
tested at the factory
- Easy to wire. Just six wire connections
need to be made to make the system operational
- Capable of running either a standard
mercury lamp or metal halide lamps
- Secondary wave-forms are designed
to improve lamp life
|If your application
requires an accurate variation of lamp output power
over a range of 30% power to full power, saturable
reactors are available to provide a smooth, linear
variation of lamp power
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