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Power supply unit for a plasma plant
| Details |
Inventors: Boniger, Paul;
Assignee: Boniger; Paul (Zurzach, CH)
Primary Examiner: Shoop; William M.
Assistant Examiner:
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
A power supply unit for a plasma plant, in particular for a plasma spraying plant, comprises an isolating transformer for connection to three-phase mains, a current control array and a rectifier array. The rectifier array comprises silicon wafer thyristors in a three-phase bridge configuration, which thyristors are electronically controlled through a current control loop, and an exterior voltage control loop is provided for additional electronic control of the silicon wafer thyristors. In the output from the thyristor array, a filter with a transient voltage suppressor may be provided as high-frequency protection and with di/dt limitation. |
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DETAILED DESCRIPTION 1.
A power supply unit for a plasma plant, in particular for a plasma spraying plant, comprising an isolating transformer for connection to the main supply, a current controller and a thyristor assembly, the thyristor assembly being connected through a current control loop with a circuit supplied on the one hand with a reference voltage and on the other hand with the voltage existing at the plasma burner, and a potentiometer for adjusting the arc current, characterized in that (a) said circuit is formed as voltage regulator (2) permitting setting of a desired voltage for no-load operation, (b) the voltage regulator (2) is adapted to receive the plasma current by means of a current transformer (11), (c) the output of the voltage regulator is connected with the input of the current controller (5), (d) the current controller (5) is adapted to have its desired current value applied by means of said potentiometer (3) and additionally by means of a follow-up integrator (4) disposed in series to the tap of the potentiometer (3), (e) the input of the current controller (5) is adapted to receive the plasma current by means of the current transformer, and (f) the output of the current controller is connected to a control unit for the thyristor assembly (13).
Description:
The present invention relates to a power supply unit for a plasma plant, in particular for a plasma spraying plant comprising a isolating transformer for connection to three-phase mains, a current control array and a rectifier array.
In a known power supply unit of the aforedefined type the voltage of the three-phase mains is transferred through reduction in the isolating transformer, the induced current is controlled through transducers and then rectified through silicon diodes.
The rectified current reaches the plasma burner itself via a series reactor.
The plasma current is measured and the magnetization of the transducers is varied through a three-step controller and a regulating transformer as a function of the current measurement data
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