- F1 and F2 – the simultaneously pressing of these bush-buttons is used for moving to mode of review and editing (fig.10) by means of several screens of threshold values of the following parameters: analog channels for measuring of DC voltage and DC current, operating frequency range, maximum DC voltage and minimum DC current in state „Ready”, parameters of the PID-regulator. - ◄ and ► – these push-buttons are used in editing mode for reaching to the desired parameter and when the power supply is in state „Error” – for reaching to the corresponding error state; - + and – – these push-buttons are used for setting of the necessary power level for heating in percents as well as for correction of the threshold values of the parameters in editing mode; - and × – these push-buttons correspond to buttons „Enter” and „Cancel”. They are used in „Error” state for reaching to the errors description screen or for leaving it. In editing mode these buttons are used for confirmation or canceling of the corrections. Input-output subsystem of the main controller includes two parts: digital inputs and digital outputs. Most of input signals enter to inputs located on the main controller PCB and some of them – to inputs of the input-output expander. The control system of the main controller has a purpose to fulfil several functions. First – measuring of the operating frequency in all power supply states except in a state „Idle”. Second – realizing of a „soft” start of the power supply after starting of highfrequency energy generation. Third – maintaining of the specified operating power. The control subsystem performs these functions with the assistance of main controller analog subsystem where the values of inverter DC voltage and DC current are measured. The communication subsystem of the main controller ensures the connection with power supply remote unit, with an interface converter RS422/MODBUS to Ethernet network and with an external programming device. This is very important feature since it ensures a possibility for a comfort distance operating or with the power supply HFG-4-500 or monitoring of the heating process from external network device – PLC or PC.
3.1.4. Block of operative circuits and elements This block combines all the electrical components (circuit-breakers, contactors, transformers, lamps, switches and push-buttons) and all the electrical connections between them used for realizing the logics of switchind on, diagnostics, starting, stopping, visualizing and control of heating process parameters. This block includes also all the components and connections of power supply water cooling system, system for temperature control of power devices operation and leakage protection.
10