Electron beam heating system (EBH System) is intended for controlled heating and melting of charge by means of electron beam, generated by gas-discharge electron gun, in vacuum melting chamber of electron-beam melting furnaces.
Basic set of electron beam complex consist of:
- Gas-discharge electron-beam gun of KV type;
- High-voltage power supply (HVPS);
- Electron beam control unit (EBCU).
EBH System can be connected to the computer remote control of melting furnace via serial port RS-485 of EBCU.
Electron beam gun KV needs to be connected to the supply system of the working gas mixture of technically pure hydrogen and oxygen, which is produced by hydrolytic generator and fed into the gun chamber, where glow discharge is occurs under the influence of high-voltage.
In addition, electron KV type gun and high-voltage power supply HVPS must be connected to self-contained water cooling system.
At the request of the Customer the basic set of EBH System can be supplemented any of these systems.
Gas-discharge electron beam gun of KV type:
At operation of gas-discharge electron beam gun an operating gas mixture is supplied to discharge chamber of a gun. High-voltage glow discharge burns in discharge chamber of a gun under accelerating voltage between cathode and anode. Plasma generating under discharge emits positive ions, which are accelerated by electric field in zone of cathode potential drop and bombard the cathode, causing electron emission. The same field accelerates electrons and forms a converging electron beam, which passes to focus-and-scanning system through a hole in bottom of the anode.
The magnetic field, created by the first focus coil, forms an electron beam under the form close to cylindrical. Hereupon it passes to the melting chamber through focus-and-scanning system practically without power losses. By means of the second focus coil the beam is focused on a heating surface. Specified scan of beam is carried out by the deflection coil.
Distinctive features of gas-discharge electron beam guns KV:
- no need for additional pumping of the vacuum in space of guns by individual high-vacuum pumps;
- weak sensitivity to changes in pressure in the melting chamber, to vapors and even to spray metal during the smelting process;
- compact size, light weight, simplicity and reliability;
- long operating life of the cathode.
|Construction scheme of KV:
||1 - cathode;
2 - anode;
3 - discharge chamber;
4 - inlet of operation gas mixture;
5 - feed bar of current.
|Parameter of gas-discharge electron beam gun KV
|Range of power regulation, kW
||0 - 150
||0 - 250
||0 - 320
||0 - 450
|Maximum accelerating voltage, V
|Deflection angle of beam from gun axis
|Range of operating pressure in internal space of gun, Pa
||0.1 - 10
|Permissible leakage rate, l*Pa/sec
|| 1,5 * 10-6
|Maximum consumption of operating gas (CP hydrogen) with pressure of 0.1▪106 Pa, l/sec
| 8 * 103
|Operating life of the cathode, hour
|Consumption of circulating cooling water, l/sec
High-voltage power supply (HVPS):
In HVPS a high-frequency conversion of electric energy due to IGBT (Insulated Gate Bipolar Transistor) is applied. Microprocessor’s control on a base of high end digital signaling processors DSP allows realizing flexible operation algorithm of supply during breakdown in gas-discharge electron beam gun (this feature ensures continuity of melting process) and interfacing by means of RS232 optical or RS485 connectors between supply control system and central computer without additional devices.
High-voltage power supply is very compact and simply engineered; it can be installed directly near GGE gun.
High-voltage power supply (open):
1 – high-voltage unit;
2 – pulse transformer;
3 – input automatic device;
4 – high-frequency chokes;
5 – rectifiers;
6 – control unit;
7 – control chains power supply.
In case of breakdown in load automatic release of inverter with following auto re-inclusion is provided. If the repeating rate of auto re-inclusion is less, than 5 sec-1, so, number of auto re-inclusion are unlimited. If the repeating rate of auto re-inclusion is more than 5 sec-1 so power supply is switched-off with appropriate signaling. The level of steady-state value of power supply load current under breakdown is not more than 1.2 in comparison with nominal value.
Regulating range of interval between auto re-inclusion is 0.002 – 0.999 s.
Energy incoming from power supply to load under every auto re-inclusion is not more than 1 Joule.
Main technical parameters:
|Nominal supply voltage (3-phase, 50 Hz), V
||380 ± 10%
|Nominal output voltage, kV
|Output voltage fluctuation, % from maximum value
|Nominal output current, A
|Maximum output power, kW
|Efficiency at maximum power, %
|Total consumed power at nominal operation mode, kV*A
|Consumption of circulating water (difference of cooling water temperature at inlet and outlet is ≈15°С), m3/h
|Overall sizes, mm
|Average time between failures, hour
|Operation life (on conditions that some parts and elements will be replaced or repaired), year
Electron beam control unit:
Electron beam control unit (EBCU) is designed to deflect the beam in two coordinates X and Y, the focus control of the electron beam (2 channels), controlling the gas supply (2 channels), and also implements the protection of the edge of the crucible for all modes of operation.
Block has a color graphic display, which is intended to show the form of scans, parameters of melting, messages and prompts to the operator.
To set parameters for melting and for operational management of the smelting process EBCU has built-in controls and keyboard.
The unit can connect to a computer system remote control and/or to the console with a joystick for beam control via the serial port RS-485.
EBCU allows the following types of scans:
- dot (from 1 to 8);
- circle (from 1 to 32);
- circular raster (from 1 to 32 circles);
- rectangular raster (from 1 to 32 lines).
Technical and operational characteristics:
|Adjustable frequency of scan
||0.1 – 100 Hz
|Adjusting current of deviation
||(+1.5) – (-1.5) А
|Adjusting current of focusing
||0 – (+1.5) А
|Adjusting current for gas supply
||0 – (+1.5) А
|Control of beam current
||0 – 15.0 А
||220 V Frequency
||≤ 150 V*A