fig1 shows a conventional plasma arc cutting system 10 using a high frequency high voltage ( hfhv ) signal to initiate a pilot arc 12 between an electrode 14 and a nozzle 16 of a plasma arc torch 18 . the arc then transfers to a workpiece 20 as a transferred arc 22 . the transferred arc has a much larger current level than the pilot arc and therefore can conduct significantly more energy to the metal workpiece 20 than the pilot arc . a power console 23 includes a d . c . power supply which provides the electrical power for the start up and steady state operation . a typical power supply produces a d . c . current of 100 to 400 amperes at 150 to 200 volts of cutting voltage . a conventional electrical lead set 26 has a negative lead 26a connected from the negative output terminal of the power supply to the electrode 14 . electrical leads 26b and 26c connect from positive output terminals of the power supply to the nozzle 16 and workpiece 20 , respectively . the torch 18 is of conventional design . by way of example and not limitation , torch 18 could be an ht400 , pac500 , or max ® 80 / 100 / 200 manufactured by hypertherm , inc . a flow 28 of a plasma gas through the torch 18 is ionized by the pilot arc 12 . a larger voltage drop is applied across the electrode and workpiece ( lead 26a to lead 26c ) than across the electrode and nozzle ( lead 26a to lead 26b ) in order to induce the arc to transfer to the workpiece once the gas in the electrode workpiece gap is ionized . with conventional starting circuits , such as shown in fig2 the time interval that the pilot arc remains attached to the nozzle , from starting the pilot arc to arc transfer is , in part , a function of the distance from the torch to the workpiece ( standoff distance ). when the workpiece is a comparatively thick plate ( e . g . 1 / 2 inch or more ) a fairly large standoff ( e . g . 3 / 8 inch ) is used to reduce the problem of molten metal splashing upwardly onto the torch from the workpiece during initial piercing of the plate . splashing occurs because during piercing , molten metal cannot flow under the influence of gravity through a cut kerr to the bottom of the plate and the force of the plasma jet on a pool of molten metal produces splashing . splashing can deposit on the torch parts and cause double arcing or gouging . the increased standoffs necessary to sufficiently reduce splashing associated with piercing and cutting thick plates is problematic because it can increase the duration of the pilot arc attachment to the nozzle which reduces the life of the nozzle . fig2 shows a conventional starting circuit 30 used to apply electrical power from the d . c . power supply 24 to the torch 18 and workpiece 20 . generally , the circuit of fig2 isolates a pilot arc circuit and a transferred arc circuit before starting the pilot arc so that the transferred arc cannot utilize the pilot arc circuit . this isolation is accomplished by using two independent resistor / capacitor networks to provide the initial pilot arc and transferred current . on start up , the power supply 24 is at a zero current output and open circuit potential until the pilot arc ignites . a main surge circuit 32 formed by surge resistor 33 and surge capacitor 34 provides an instantaneous current source to the electrode - nozzle gap 37 as soon as it ionizes . resistor 35 is a high resistance bleed resistor . an hfhv generator 36 is typically of the marcon type which generates high voltage ringing electrical impulses . a typical hfhv output signal useful for plasma arc ignition has a voltage in the 5 - 10 kv range and has a frequency in the 1 - 3 mhz range . this signal propagates from the electrode 14 ( the cathode ) through capacitor 31 to the nozzle 16 ( the anode ). the high voltage between the electrode and the nozzle generates charge carriers in the plasma gas between these elements . these charge carriers create an electrical current path between the electrode and nozzle necessary to start an arc in the plasma gas . the voltage and time at which breakdown occurs is random for a given set of operating conditions , if it occurs at all . the power supply ramps up to a steady state pilot arc current over a typical period of 1 to 2 msec . during this ramp up period , the surge injection circuit 32 ideally provides an initial current at a level sufficient to sustain the pilot arc 12 and , after the arc strikes , provides current at a level sufficient to sustain the transferred arc 22 . the surge injection circuit 32 is connected in parallel with the power supply 24 . the power supply 24 charges the surge capacitor to its open circuit voltage . a pilot relay 39 and a pilot resistor 40 are connected between the positive lead 26c and the nozzle lead 26b . torch operation is initiated by closing the pilot relay 39 which electrically connects resistor 40 into the circuit between the workpiece and the hfhv generator . the hfhv generator is then energized which ionizes the gas in the gap between the electrode 14 and the nozzle 16 providing a conductive path 37 which discharges capacitor 34 thereby providing current to the torch sufficient to initiate and sustain a pilot arc . the total current transferred to the pilot arc in this conventional arrangement is the sum of the current from capacitor 34 and the main current from the d . c . power supply 24 . the resistive electrical path between the positive lead 26c and the nozzle lead 26b induces the arc to transfer to the workpiece after the pilot arc is struck because the total resistance between the electrode and workpiece along a path via the nozzle and resistor 40 is greater than the resistance presented by the ionized gas between the electrode and the workpiece directly . the pilot relay is opened after the pilot arc transfers . the duration and the value of the energy flow in the pilot arc circuit is controlled by capacitor 34 to be sufficiently long enough to ignite the transferred arc but short enough not to damage the nozzle . this circuit works well for reducing the nozzle wear with a torch standoff as high as one - half inch . the circuit of fig2 is , however , problematic because the total current through the electrode suddenly increases when the arc transfers to the workpiece . the current increases after transfer since the pilot resistor 40 no longer acts to limit the current flow . for certain plasma cutting systems , the step increase of the electrode current causes an increase in electrode wear . also , the large voltage difference between the electrode and the nozzle results in the arc being directed back to the nozzle . the arc jumping back and forth between the nozzle and the workpiece before the pilot relay opens causes damage to the nozzle orifice . fig3 - 6 describe the features of the present invention . fig3 is a circuit diagram of a starting circuit according to the present invention which controls the voltage between the nozzle and the workpiece for starting and transferring the plasma arc . the circuit of fig3 differs primarily from the conventional starting circuit in that it includes a charge control network 41 connected in series between nozzle lead 26b and the workpiece lead 26c . the network includes a capacitor 42 connected in parallel with a resistor 40 . capacitor 34 is initially charged by the power supply 24 to its open circuit voltage . when torch operation is initiated by closing the pilot relay 39 and energizing the high frequency high voltage generator , capacitor 34 begins to discharge and capacitor 42 begins to charge causing the voltage between the nozzle and the workpiece to increase . after the arc transfers to the workpiece , the pilot relay 39 is opened . capacitor 42 then discharges through resistor 40 . consequently , the pilot arc current and the nozzle voltage decrease . the arc transfers to the work quickly due to the increased voltage between the nozzle and the workpiece . capacitor 42 of the charge storage network 41 limits the initial current on pilot arc ignition . thus according to the present invention , the total energy available to the pilot arc after ignition is determined by the capacitance value of capacitor 42 and not by the sum of the current supplied by the capacitor 34 and the current output of the power supply 24 as in the prior art starting circuits . the charge storage network of fig3 therefore , serves to eliminate step increases of electrical current thereby reducing arc jumping between the nozzle and the workpiece . fig4 is circuit diagram of another starting circuit according to the present invention . the starting circuit includes an inductor - capacitor surge injection circuit which produces a generally constant pilot arc current for a short time even when the voltage across the capacitor 42 ramps up quickly . like the circuit of fig3 the pilot arc circuit includes a high resistance bleed resistor 35 to drain residual energy from the surge capacitor 34 . the circuit also includes a charge control network 46 that includes a resistor 40 connected in parallel with a capacitor 42 . the capacitance value of capacitor 42 , however , is variable . a diode network isolates the pilot arc circuit from the transfer circuit . the inductor - capacitor surge injection circuit includes inductor 49 connected in series with capacitor 34 . relay contact 50 is set to the closed position prior to the torch ignition to allow capacitor 34 to charge to the power supply open circuit voltage . relay contact 50 is then opened and the torch is ignited by the hfhv source 36 . the inductor is used to provide a square pulse shape to the surge injection discharge current . the capacitance value of capacitor 34 and inductance value of inductor 49 are selected so that they produce a generally constant pilot current level over a brief time interval . the diode network protects the circuit from voltage reversal . diode 51 discharges the inductor 49 rapidly when the voltage reverses . diode 52 protects capacitor 42 against the voltage reversal . some applications require the use of different plasma gases or different types of consumables . to produce suitable pilot arc current waveforms , such changes may require the use of a different capacitance values for pilot arc capacitor 42 . in order to change the capacitance , a relay 53 may be used to select different values of capacitance 42 . the circuit of fig4 transfers arcs reliably for both oxygen and nitrogen plasma gases . by way of example , the circuit in fig4 maybe utilized in an ht4000 plasma arc torch manufactured by hypertherm . the inductor 49 has an inductance of 1 . 5 mh . resistor 33 and 40 have resistances of 2ω . the capacitor 31 has a capacitance of 0 . 022μf and is used for high frequency bypassing . capacitor 34 is 510μf and resistor 35 is 10k . the open circuit voltage of power supply 24 is typically 275 volts d . c . with such parameters , the pilot arc has a current of 40 to 100 amperes . when a 3 / 8 &# 34 ; torch standoff is used , the pilot arc time is typically about 0 . 2 to 0 . 3 milliseconds . the nozzle - to - work voltage increases from zero to 80 volts during this short time and maintains this value after the arc transfers for about 100 milliseconds . the pilot arc current is generally constant in the range of 50 amps before transferring . as a result , the nozzle wear is reduced dramatically a compared to the standard start circuit and the electrode life is not affected because of the smooth ramp up of the electrode current . fig5 is a timing diagram according to the present invention for the circuit shown in fig4 showing the simultaneous state of system parameters during torch start up as a function of time . a start signal 60 initiates torch operation at a time 59 . plasma gas flow 62 is initiated with the start signal 60 at time 59 . after a fixed period of pre - flow gas , the d . c . power supply is activated at time 64 allowing capacitor 34 to charge . once the capacitor is fully charged , at time 66 , the pilot arc relay is energized 65 by configuring the relay in position 48 . this isolates the pilot arc circuit from the transferred arc circuit and thus any energy to the nozzle 16 is generated by the pilot arc circuit alone . the high frequency high voltage signal is initiated at time 68 . the plasma gas flowing between the electrode and the nozzle is quickly ionized thus initiating the pilot arc 12 as indicated by the step function increase in the pilot arc current in waveform 72 . at time 73 , the hfhv signal is terminated . nozzle voltage 76 ramps up during the pilot arc time 71 and remains constant after the pilot arc transfers . typically the pilot arc time 71 is on order of approximately 1 msec . this interval does , however , vary with operating conditions such as gas flow rate and standoff . at time 73 , the pilot arc transfers allowing arc current 72 to flow . the pilot arc relay is de - energized with a time delay 75 after the arc transfers and the nozzle voltage drops at the same time by discharging the pilot capacitor through the resistor . the nozzle voltage ramps down at time 74 after the arc has transferred . the arc is turned off at time 77 . there is a post flow time of plasma gas during time 78 after the arc is turned off to purge the torch . the pilot arc duration and power level are controlled primarily by capacitor 42 , resistor 40 , and inductor 49 . the value of the maximum current in this pulse varies depending upon the application . a typical value for high current systems is 80 amperes . the duration of the pilot arc pulse 72 is typically 2 - 3 msec . the pilot arc duration of conventional circuits is about 100 msec when a standoff distance of 3 / 8 inch is used . this represents as much as a 98 % reduction in time . this reduction increases nozzle life by approximately 3 - 5 times when compared to conventional nozzle life under the same operating conditions . fig6 is another alternative embodiment of a plasma arc cutting system according to the present invention . in an alternate form , an active current source 24b is used in the pilot arc loop . the source provides a step current output when the hfhv source induces a spark between the electrode and the nozzle . the active current source is advantageous because it provides a constant pilot arc current independent of consumable types and current levels . the pilot arc circuit includes the active current source 24b , a negative lead 26a , a positive lead 26b , and a switch 80 . the active current source is connected to the electrode 14 by lead 26a . the positive terminal of the source is connected to the nozzle 16 by positive lead 26b through switch 80 . the switch is controlled by control lead 82 which is responsive to a control circuit ( not shown ) preprogrammed to operate according to the timing diagram of fig5 . the switch can be any of a wide variety of conventional type devices such as a solid state relay . while the invention has been particularly shown and described with reference to specific preferred embodiments , it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims .