1. Air Plasma Torch :
   

   A Copper Electrode 25kW Hollow Cathode Reverse Polarity Thermal Air Plasma Torch (CERPPT- 25kW) has been designed and developed for industrial as well as R&D application. This plasma torch uses air / nitrogen as plasma gas. The plume has high thermal enthalpy (7-8 MJ/kg). The torch has more than 150hr of electrode life. The torch is rugged and is able to operate for long duration. It has advanced double cup design and operates in reverse polarity, i.e. the plume side electrode is cathode. This leads to higher thermal efficiency (~70%), longer plume length (300-400mm long) and higher temperature (~8500C) in the plume. This torch has user friendly design with ease of fabrication, assembly, installation and operation. The technology also includes complete design of a plasma power source with all necessary features. The combined system provides a robust and complete package for thermal plasma applications. The torch produces plasma plume as intense and luminous atmospheric pressure broom shaped plasma. The plume dimensions and power content can be tailored by suitably adjusting operating parameters e.g. air flow and arc current.

2. 45 kW, 150A IGBT based power source for thermal plasma application
   

   The power source of 25 kW, 150A DC for Thermal Plasma torch consists of a main arc DC power supply and a trigger unit. The trigger unit initiates arc and main arc power supply gives energy to maintain it. The main arc power supply have fast response to enable stabilizing the plasma. The main arc power source is based on 25 kHz IGBT inverter operating in constant current mode. 3kV, 3 MHz trigger unit is based on capacitor discharge through spark gap. Trigger unit is inductively coupled with main arc power supply.

1. CERPPT-25kW: Air Plasma Torch
   
   1. Vortex stabilized torch
   2. Advanced helical cooling channel cooling channel design
   3. All copper hollow Electrodes
   4. Electromagnet assist for arc rotation
   5. Double cup cathode
   6. Torch can be operated with range of power from 18 kW to 25 kW.
   7. 8500C plume temperature.
   8. High efficiency (65-70%).
   9. High enthalpy (7-8 MJ/kg).
   10. Low cost
   11. Air as plasma gas
   12. Long electrode life (150hr): using swirl flow and electromagnetic assisted arc rotation.
   13. Light weight
   14. Easy replacement of consumables
   15. High gas flow (20- 40 lpm)
   16. The torch has passed 150hr endurance test: Proven reliability
   17. Extensive testing carried out includes Plume temperature profile using OES, Plume length, metal melt / plume profile, Efficiency test, Dynamic and steady state operating profile, Noise measurement, Coal bucket test, UV emission measurement, Electrode life test and Graphite sublimation test
2. 45 kW, 150A IGBT based power source for thermal plasma application
   
   1. 45 kW power @150A DC
   2. A complete solution for torch operation no additional control desk is required.
   3. Adjustment of operating parameters like gas flow and current available in remote and on desk
   4. 3kV @3MHz HVHF for triggering.
   5. Soft start
   6. Current ripple less than 1%
   7. Suitable for air plasma torch
   8. 25 kHz IGBT inverter based design
   9. Fast Rectifier and filter
   10. Hybrid control system
   11. User friendly GUI (Graphical User Interface) with 10" touch screen display
   12. Rugged and light in weight
   13. Fits into a very compact size
   14. Low cost indigenous product
   15. Compatible with SCADA system
   16. Extensive testing carried out includes Full load test, Heat run test, graphite rod test and long duration operation with plasma torch.

1. Air Plasma Torch
   1. Plasma incineration / gasification of waste
   2. Metal surface hardening (nitriding, carburizing)
   3. Melting and refining small metal batches
   4. Spheroidization of metal powders for 3D printing
   5. Hazardous waste destruction (medical, chemical)
   6. Plasma spraying / thermal spray coatings, Nanoparticle synthesis (metal oxides, CNTs)
   7. Thermal barrier coatings
   8. High-quality cutting of thick metal plates
   9. Plasma reforming of fuels to produce hydrogen-rich syngas and ammonia cracking
   10. Ignition source for boilers, gasifiers, industrial furnaces and kilns
   11. High-temperature material testing in research labs
   12. Plasma physics and fluid dynamics experiments
   13. Heating applications requiring 5000–15000 °C
   14. High temperature testing of heat shield materials
   15. Synthesis of specialty alloys in R&D setups
   16. Nuclear waste volume reduction and immobilization
   17. Mineralization of liquid waste
2. 45 kW, 150A IGBT based power source for thermal plasma application
   1. The power source can energizing the 25 kW/30 kW Air plasma torch developed by BARC.
   2. It can energize any electrical load (heating, cutting welding etc.) with voltage requirement of 300 volts and current requirement of upto 150 A.
   3. This source can cater to any load demanding a constant current power.

A Copper Electrode 25kW Hollow Cathode Reverse Polarity Thermal Air Plasma Torch (CERPPT- 25kW) along with the Plasma Power Source is available for transfer of technology for industrial as well as R&D application. It uses air / nitrogen as plasma gas and generates a 300-400mm long jet of high thermal energy density. The torch has more than 150hr of electrode life. The torch is rugged and is able to operate for long duration. The torch has advanced double cup design and it operates in reverse polarity, i.e. the plume side electrode is cathode. This leads to higher thermal efficiency, longer plume length and higher temperature in the plume. This torch has user friendly design with ease of fabrication, assembly, installation and operation. The technology also includes complete design of a plasma power source with all necessary features. The combined system provides a robust and complete package for thermal plasma applications.

This 25kW power air thermal plasma torch is very important for high temperature industrial processes like incineration, pyrolysis, melting, cutting, welding, spraying, and waste treatment. Their ability to generate long plume of high density plasma having temperature >6000K enables a diverse wide range of applications in nuclear and other industries. The torch has been designed, simulated and tested using multiphysics and CAD software to obtain optimum performance including operating power, voltage, current, arc attachment location and thermal efficiency. The efficiency of torch is very high ~70%. The torch has modular design enabling, replacement of a small consumable part over the long life of the torch.

This torch is energised by a custom built plasma power source. The power source is 45 kW, 150A DC suitable for Thermal Plasma torch consists of a main arc DC power supply and a trigger unit. The trigger unit initiates arc and main arc power supply gives energy to maintain it. The main arc power supply have fast response to enable stabilizing the plasma. The main arc power source is based on 25 kHz IGBT inverter operating in constant current mode. 3kV, 3 MHz trigger unit is based on capacitor discharge through spark gap. Trigger unit is inductively coupled with main arc power supply.

A high voltage high frequency (HVHF) supply is required for initiation of the discharge between the cathode and anode having a designed gap. Since the electrical resistance of the gas in the plasma torch is high the open circuit voltage of the main arc power supply cannot cause a breakdown in the inter electrode gap. A trigger unit having HV 3-5 kV @3 MHz can easily produce breakdown between the electrodes. This trigger produces initial ionization of the gas which lead to plasma in the inter-electrode gap. Once the plasma discharge is initiated, its low electrical resistance enables the main arc power supply to take over and maintain the plasma discharge.

The block diagram of a typical power source for thermal plasma application is given in below. The major blocks of this power source are front end rectifier & DC link filter, Soft start rectifier, IGBT inverter, High frequency link transformer output rectifier & filter and HVHF unit.

1. Torch salient features
   1. Vortex stabilized torch: The most important design feature of this torches is the vortex chamber which introduces a strong vortex / swirl flow pattern of the plasma gas in the inter-electrode cavity, which moves the arc root very rapidly on the electrode surface. This leads to leading to a distribution of the electrode erosion over as large an area as possible. This design keeps the arc centred in the electrode and allows extension along the axis. The vortex flow results in a steady and long plasma plume. The vortex flow increases the interaction leading to high thermal efficiency.
   2. Advanced cooling channel design: A helical cooling channel has been engineered with channel diameter, helix pitch, number of turns to generate optimum spiral flow passage at the design pressure. This has been integrated within a copper electrode to enhance convective heat removal to cool the electrode heated by arc root. The helical geometry significantly improves the convective heat-transfer coefficient compared to straight channels which allows safe and long duration operation of plasma torch. This spiral profile provides cooling along circumference and low axial thermal gradients. This also help to prevent local hot spots. This design enables dissipation of the continuous, high-intensity heat flux.
   3. All copper hollow Electrodes: The torch uses pure Copper electrodes reducing cost of material and machining. The modular design of torch allows quick replacement and easy assembly of torch. The cost of raw material and machining are also low.
   4. Electromagnet assist for arc stabilization: A unique method of utilizing the self current of torch to generate a magnetic field to assist arc root movement has been employed in this torch. This significantly reduces electrode erosion by continuously moving the arc root along the wall of electrodes.
   5. Torch can be operated with range of power from 18 kW to 25 kW.
   6. 8500C plume temperature.
   7. High efficiency (65-70%).
   8. High enthalpy (7-8 MJ/kg).
2. Power supply salient features
   1. Soft start rectifier: A soft start rectifier is required to charge DC link capacitor in the controlled manner when conventional uncontrolled front end rectifier or high pulse rectifier is used. This is to avoid the over stressing the diodes of main front end rectifier.
   2. High frequency IGBT based Inverter: IGBT based single phase high frequency ac link inverter is used, which is fed to a ferrite core transformer. The operating frequency of inverter is 25 kHz. The output of inverter is coupled to HF transformer through coupling capacitor for DC blocking.
   3. Fast Rectifier and filter: The output of transformer is rectified using fast rectifier and filtered using balanced T filter.
   4. Hybrid control system: The system features a robust hybrid (Analog & Digital) control circuit not only ensures smooth implementation of proportional integral control but also takes care of system interlocks for safe operation, interfacing with other devices. User friendly GUI is implemented through 10” touch screen display.
   5. It has a 45 kW power @150A DC main arc power supply along with 3kV @3MHz HVHF for triggering.
   6. Current ripple is less than 1%.
   7. Rugged and light in weight, very compact size.
   8. Low cost indigenous product.
   9. Compatible with SCADA system.
   10. Extensive testing carried out includes Full load test, Heat run test, graphite rod test and long duration operation with plasma torch.

Technical specification of the torch

Plasma Torch :

1. Cathode : Diameter: 68 mm Length : 105 mm
2. Anode : Diameter: 60 mm Length : 90 mm
3. Plasma exit bore : 22 mm
4. Coolant connector : 1/4 inch BSP
5. Gas connector : 1/4 inch BSP
6. Electrical connector type : standard lugs (10 mm)
7. Cathode type : Hollow double cup copper
8. Anode type : Hollow copper
9. Cooling : Helical cooling water channel
10. Water inlet temperature : 20 -35C

Vortex Gas Ring :

1. Gas Ring type : Vortex built in
2. Material : Teflon
3. Gas Supported : Argon, Nitrogen, Air (based on application)

Cooling water :

1. Capacity : 30-40 liter per minute at 7 kg/cm² of pressure
2. Inlet & outlet temperature : Inlet: <28 Outlet: 35-40C
3. Water type : Process water with <50 micron filtration
4. Rotameter : 0-50 lpm @ Water

Air :

1. Air quality : Dry air, RH < 10ppm, processed through air dryer
2. Air Pressure : 5 – 6kg/cm²
3. Air flow : up to 50 lpm
4. Rotameter : 0-100 lpm@ Air

Argon Supply :

1. Type : Commercial argon cylinder bank
2. Discharge pressure : Working: 4.5 kg/cm² / Max: 7.5 kg/cm²
3. Rotameter : 0-50 lpm@ Ar

SPECIFICATIONS OF THE SYSTEM

Sr. No.	Parameters	Specifications for indented items
1.	Input Voltage	415 V ± 10%, 3Ph, 50Hz± 3%, 4 WIRE SYSTEM
2.	Input kVA Max. MAX.	75 kVA at 80% efficiency
3.	Class of Insulation	Class H
4.	Power Factor	> 0.9
5.	System Frequency	25 kHz or Higher
6.	Mode of Control	Constant Current Control (PWM Control)
7.	Open Circuit Voltage	≥ 600 V ± 10%
8.	Max Output voltage	≥ 300 V (at full load)
9.	Max Output Current	150 A
10.	Max output Power	150 A/300 V DC Power will be limited to 45 kW
11.	Cooling	Forced Air Cooling
12.	Input Current THD	as per latest IEEE std 519
13.	Output Current Ripple %	≤ 1% at full load
14.	HF Unit	3MHz, > 3 kV (RMS), Power: 100W±5% with Built-in protection circuit
15.	Current Feedback System	Hall effect sensor with accuracy 1%
16.	Output current filter	Third order inductive filters
17.	Max. Ambient operating condition	temperature : 45 Deg. C Humidity : 87% at 45 C
18.	IP RATING	Minimum IP31 rated panel should be used
19.	3 phase input interlocks (Restricts user to switch ON mains contactor)	Door open, Input under voltage, Input over voltage, Input Phase Fail, Input phase rever-sal, apart from the digital interlocks Fast Fuses of sufficient rating should be provided.
20.	Protection interlocks (re-moves the PWM pulses to IGBT and allows only after removal of faults)	Output Overcurrent (> 110% for more than 1 seconds), output overvoltage (>120% of open circuit voltage, should be adjustable) and IGBT over temperature (>60 °C at heatsink, Dsat sensing in driver), Fast rectifier heatsink over temperature (>60 °C), Trans-former over temperature (> 80 °C), Surge protection device
21.	Communication port	Ethernet port
22.	Measurement display on front panel	Voltage, Current, Power
23.	Input cables along with cable trays	3.5 Core, > 70 sq. mm. flexible copper cable or 3.5 Core > 100 sq. mm. flexible aluminum cable Length : 10 to 25 m depending on installation requirement
24.	Output cables	> 70 sq. mm. copper flexible wire or > 120 sq. mm. aluminum flexible wire
25.	Communication cable	CAT 6 STP cable, length: 100 m
26.	Wheels	4 Nos. of caster wheels at bottom should be provided of sufficient weight capacity with facility for wheels locking.
27.	Argon & Air digital MFC RANGE	Air : 0 – 300 LPM Argon : 0- 50 LPM
28.	Controller type	PLC

Testing of technology

The technology has undergone rigorous testing. A protocol / SOP has been developed for assembly and testing for both CERPPT-25kW torch and power source. The Table 1 shows various photographs of testing of power source and plasma torch.

Testing of torch :

Routine test	Type test
Assembly and dimensional check Air leak and Hydro test Electrical Insulation Test Trigger Test Plume test with Argon and Air Arc rotation test 1 hour test bench operation Voltage current and flow measurement.	Plume temperature profile using OES Plume length, metal melt / plume profile Efficiency test Dynamic and steady state operating profile Noise measurement Coal bucket test UV emission measurement Electrode life test Graphite sublimation test

Testing of power source :

Routine test	Type test
Sub-assembly/ components test Megger test Functional test Light load test Short circuit test HVHF test Ripple and regulation test Interlock and protection feature check Rated load test for 1 hr	Water load test Full load test Heat run test Graphite rod plasma/spark test Air plasma torch test

1. Metal surface hardening (nitriding, carburizing)
2. Melting and refining small metal batches
3. Spheroidization of metal powders for 3D printing
4. Plasma gasification of waste
5. Hazardous waste destruction (medical, chemical)
6. Plasma spraying / thermal spray coatings, Nanoparticle synthesis (metal oxides, CNTs)
7. High-quality cutting of thick metal plates
8. Plasma reforming of fuels to produce hydrogen-rich syngas and ammonia cracking
9. Ignition source for boilers, gasifiers, industrial furnaces and kilns
10. High-temperature material testing in research labs
11. Plasma physics and fluid dynamics experiments
12. Heating applications requiring 5000–15000 °C
13. Synthesis of specialty alloys in R&D setups

RAW MATERIALS

The raw material required are electrical components like copper rod, Teflon rod, Fasteners, O-ring, fittings, SS plates for holding structures, SS rod/pipe

EQUIPMENTS

Lathe machine, Milling machine, Brazing setup, Air compressor, Hydro test setup, Trigger power source, Argon gas supply, Welding machine and cooling water, Electrical test and measurement equipment such as Multimeter, Clamp on meters, Oscilloscope, Megger etc

SPACE

Floor space of 300 sq. ft. (15ft x 20ft) is required for integration and testing

POWER

3 phase electrical power of suitable rating, Compressed air

MANPOWER

One fitter, one turner/miller, one electrician and one helper is required for assembly/connection & testing of the plasma torch. One electrical engineer with bachelor’s degree, one electrician/wireman and one helper is required for wiring and assembly of the power source.