Example of a corona equipment
The equipment is composed of 4 basic parts: a generator module (power module), a high voltage
transformer, treater station and an exhaust system (optional). The pre-treatment itself is carried out in
the treater station, where a system of electrodes gives an efficient electrical discharge on the film. The
electrical power comes from the generator and the high voltage transformer. During the discharge in
the treater station, heat and ozone are created, which is why an exhaustion of the air in the treater
station is necessary.
The electrical system consists of a strong power supply, ensuring an efficient DC tension to the output
stage. The output amplifiers are designed with IGBT transistors in order to ensure a reliable working of
the high effects. The output signal from the generator is connected to the high voltage transformer,
which step up the power to the electrodes.
The control and monitoring parts are taken care of by a generator, to which the remote control/BUS
interface and the control signals are connected.
The electrical Corona principle is centered around a resonant circuit, that the web material is a part of.
The working frequency of the electronic system is controlled automatically by a feedback system to a
frequency between 10 - 40 kHz. This ensures a maximum efficiency and thus an optimum pre-
treatment.
The Corona effect comes from a specially designed iHP-transformer with a minimum power loss and
optimum output voltage. The discharge emanates from the electrodes on to the film surface on the roll.
The generator output power is controlled by a pulse width-modulation principle (PWM-power). Keeping
the power supply constant to the IGBT-switch-transistors and adjusting the power –i.e. the treating
effect - according to the time factor. This way you avoid the dangerous high tension potential, which
causes pinholes.
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