Abstract: A plasma arc cutting power supply, and method of providing plasma cutting power, is disclosed. It includes a source of power having, preferably an engine or transformer based power source, that provides a main power output and an auxiliary power output. A two-state configuration circuit is in electrical communication with the auxiliary power output. The auxiliary power output receives voltage of a first magnitude with a non-floating ground when the configuration circuit is in its first state. The auxiliary power output receives voltage of a second magnitude, preferably different than the first magnitude, with a floating ground, when the configuration circuit is in its second state. When a plasma cutting circuit is connected to the auxiliary power output the configuration circuit is set in its second state. The plasma cutting circuit includes at least one chopper. A safety circuit that disables the plasma output includes a GFI or optical isolator.

Abstract: A high frequency plasma processing apparatus and a high frequency plasma processing method according to the invention can suitably be used for uniformly forming on a substrate a deposition film over a large area. The apparatus and the related method solve the problem wherein high frequency power supplied to a known plasma processing apparatus can become distorted to produce harmonics and give rise to difficulty in correctly reading the incident and reflected powers and realizing an accurate matching when a VHF is used in order to raise the processing rate.

Abstract: This invention provides a method and apparatus for improved arc initiation during Gas-Metal Arc welding. The unstable period at the arc start is a period when increased spatter is produced and increased fume is generated and defects such as unacceptable weld bead profiles, porosity and inadequate penetration occur. It has been observed that initiating the arc using a substantially higher average arc current and thereafter switching the power supply to a CV mode for the remainder of the Gas-Metal Arc welding operation decreases the arc initiation period and the instability produced during this arc start period. Initiating the arc using a CC supply and then dynamically switching on-line the power supply to CV operation provides a means of decreasing the arc initiation period and the amount of instability produced during the arc initiation period. Power supplies for Gas-Metal Arc welding and other applications requiring on-line switching between CC and CV are disclosed.

Abstract: A power supply, such as a plasma cutting power supply or a welding power supply, that provides an output to a pair of output terminals is disclosed. The power supply includes a source of voltage and a plurality of choppers. The choppers are connected in parallel between the voltage source output terminals. A controller controls the choppers so that they are out-of-phase with respect to each of the other of the plurality of choppers. The choppers preferably include a freewheeling diode, an inductor and a switch. The number of choppers is approximately equal to the ratio of the open circuit voltage to the output load voltage.

Abstract: A process and apparatus for cutting a material using a plasma are jet provides improved uniformity along the length of cut, despite variations in cutting speed. This is achieved by pulsing the arc current and dynamically varying the pulsing. By this means the momentum of the plasma arc jet can be maintained substantially constant whilst the amount of energy delivered by the plasma arc jet is controllably varied. The pulsing can be dynamically varied in dependence on one or more of the cutting speed, the angle of ejection of a stream of molten material from the cut, the size of the droplets of the ejected material, the intensity of spectral pattern of light emitted from the plasma arc jet and material interface, and the arc voltage. The pulses can be varied by varying one or more of the pulsing frequency, the pulse duty, upper value of the pulse current, and depth of the pulses.

Abstract: An plasma cutter, including a power supply, a cutting torch (with a nozzle), a source of air and a valve, is disclosed. The cutting torch is connected to the two power source outputs (cathode and anode). Air is supplied to the nozzle through the valve from the air supply. In one position the valve allows air to flow from the air source to the nozzle. In a second position the valve prevents air from flowing from the air supply to the nozzle and also vents the nozzle and torch. The torch has a movable electrode and the nozzle is in a fixed position. The nozzle and electrode are each electrically connected to a different one of the power outputs. The electrode is biased (preferably by a spring) to be in contact with the nozzle. However, air flowing into the torch and electrode overcomes the bias and moves the electrode away from the nozzle. If the arc is absent and the user desires current, then the valve is moved to prevent air from flowing into the torch and to vent the torch.

Abstract: Plasma processing apparatus frequently incorporates an antenna fed from a power supply and in this invention a power supply feeds a conventional matching circuit (10), which in turn is connected to the primary (11) of a transformer (12). The antenna (15) is coupled across the secondary winding (13) of the transformer (12) and that winding is tapped to ground at (16). This creates a virtual earth (17) near the mid point of the antenna (15) significantly reducing the variation, along the length of the antenna, in the power supplied to the plasma.

Abstract: A method and apparatus for providing welding/plasma power is disclosed. The welding/plasma power source includes an input stage, an output stage, and an energy storage device such as a capacitor. The input stage is configured to receive an ac input signal and to rectify the ac input signal to provide a rectified intermediate signal. The input stage is further configured to provide a dc voltage signal across a dc bus. The output stage is disposed to receive the dc voltage signal and is configured to provide an available output power signal suitable for welding, plasma cutting and induction heating applications. The energy storage device is connected to provide sufficient stored energy to the dc bus to allow the welding/plasma power source to run off of a generator.

Abstract: A process and apparatus for stopping a cutting operation of a plasma arc torch is disclosed which minimizes the oxidation of the electrode to thereby extend life of the electrode. A flow of oxidizing gas is directed through a plasma chamber and nozzle. An electrical current is then conducted through the electrode to form a plasma arc. The electrical current is cut no later than a time F for extinguishing the plasma arc. The flow of oxidizing gas is switched off a determinable time interval before time F, and a flow of non-oxidizing gas is switched on no later than time F, whereby the non-oxidizing gas substantially completely purges the oxidizing gas from the torch creating an inert environment, whereby the plasma arc extinguishes in the inert environment.

Abstract: Apparatus (10) for generating an ionized gas plasma flame for use in medicine, particularly for cauterization, is described. The apparatus (10) has an electrical power source (12) providing an alternating voltage at a fixed frequency and a resonant circuit (16, 26) resonant at the fixed frequency connected to the electrical power source (12). A single insulated electrical conductor (30) is connected to the output (18) of the reactive circuit (16) and terminates at a nozzle (36). Conduit means (32) surrounds the electrical conductor (30) along its length and defines a gas-flow channel for supplying substantially inert gas to the nozzle (36), where the gas-flow emerges as a plasma.

Abstract: A DC voltage resulting from rectifying and smoothing a commercial AC voltage is converted into a high-frequency voltage in an inverter which is operated in response to the closure of a start switch. A transformer transforms the high-frequency voltage, and the voltage-transformed high-frequency voltage is converted to a DC voltage by a rectifier and reactor for application between a torch and a workpiece with a gap disposed therebetween. In response to the closure of the start switch, an igniter operated from the voltage-transformed high-frequency voltage is enabled by an igniter driver to thereby apply a high-frequency voltage between the torch and the workpiece to generate an arc therebetween. A current detector detects current attributable to the arcing. A timer starts operating upon closure of the start switch and causes a disabling commander to disable the inverter when no current is detected by the current detector during a time period longer than a period required for an arc to be generated in the gap.

Abstract: A low inductance large area coil (LILAC) is provided as a source for generating a large area plasma. The LILAC comprises at least two windings which, when connected to an RF source via impedance matching circuitry, produce a circulating flow of electrons to cause a magnetic field in the plasma. Because the LILAC employs multiple windings, few turns of winding are required to obtain a large area coil, so that the inductance of the LILAC is low. The low inductance of the LILAC ensures that the self-resonating frequency of the LILAC is kept at a level far above the RF driving frequency, allowing a broad frequency range for impedance matching. Thus, there is no difficulty in impedance matching, and power transfer can be maximized, permitting efficient generation of a large area plasma.

Abstract: This invention relates to a plasma focus source for generating radiation at a selected wavelength, the invention involving producing a high energy plasma sheathe which moves down an electrode column at high speed and is pinched at the end of the column to form a very high temperature spot. An ionizable gas introduced at the pinch can produce radiation at the desired wavelength. In order to prevent separation of the plasma sheathe from the pinch, and therefore to prolong the pinch and prevent potentially damaging restrike, a shield of a high temperature nonconducting material is positioned a selected distance from the center electrode and shaped to redirect the plasma sheathe to the center electrode, preventing separation thereof. An opening is provided in the shield to permit the desired radiation to pass substantially unimpeded.