Abstract: A system and method for coordinating shunt reactance switching in a system with a transformer having a primary voltage and a secondary voltage for supplying low voltage power to a load. Voltage and power meters are provided for measuring the primary voltage and the reactive power flowing to the load. A programmable logic controller receives as one set of inputs measurements of primary voltage and reactive power flowing to the load, and as another set of inputs, predetermined ranges establishing high and low limits for the primary voltage and the reactive power. Based on these inputs, the programmable logic controller connects or disconnects at least one shunt reactance to maintain the load voltage substantially constant.

Abstract: A static VAR compensator (11) is connected across a power transmission line (10) and includes a capacitor (12) connected to transmission line (10). The static VAR compensator (11) includes a capacitor (12) connected to the AC transmission line (10) and thyristor switches (18, 22) for controllably switching the capacitor (12) across the transmission line (10). The thyristors (18, 22) are fired based on signals generated by control circuitry (26, 28, 30). A substantially constant or DC voltage exists across the capacitor (12) after the thyristor switches have been turned-off. Discharge control circuitry (30) generates firing pulses to activate the thyristor switches (18, 22) in order to discharge the capacitor (12) and reduce the voltage across the capacitor (12) to zero. In one embodiment, the capacitor (12) is discharged gradually using a series of discharge pulses.

Abstract: A thyristor controlled series capacitor (TCSC) system, including a method and apparatus, uses phase controlled firing based on monitored capacitor voltage and line current. For vernier operation, the TCSC system predicts an upcoming firing angle for switching a thyristor controlled commutating circuit to bypass line current around a series capacitor. Each bypass current pulse changes the capacitor voltage proportionally to the integrated value of the current pulse. To damp the natural oscillatory response of the inductive commutating circuit and the capacitor, a bypass mode firing angle is introduced to create a nonlinear response. The harmonic distortion on the commutating circuit current waveform is determined from the capacitor voltage, which is then used to determine the magnitude of the firing angle. Preferably the firing angle magnitude decreases in response to decreasing capacitor voltage, eventually returning to steady-state conditions.

Abstract: Series capacitor equipment for connection into an electric power line (A) has a capacitor bank (C) and a controllable inductor connection (L, T1, T2) connected in parallel therewith and comprising a series connection of an inductor (L) and a controllable semiconductor connection (T1, T2). Further, the equipment comprises control members (CU) adapted, on the occurrence of a subsynchronous resonance oscillation, to control the semiconductor connection with separate control angle values during positive and negative half-cycles of the capacitor voltage for generation of a subharmonic voltage which counteracts the resonance oscillation.

Abstract: An automatic voltage control circuit by using reactive power is disclosed. The circuit comprises a proportional integrator, a triangular wave generator, a comparing circuit having first and second comparators, an inventer, and a reactive power control circuit, wherein the proportional integrator proportionally integrates the differences between output voltages and a reference voltage, the triangular wave generator outputs first and second triangular waves with a difference of phase angle 90.degree., the comparing circuit compares the output from the proportional integrator with the first and second triangular waves, the inverter controls the effective power by the output from the first comparator, and the reactive power control circuit controls the reactive power due to the variations of the load in response to the output from the second comparator, so that the output voltage can be maintained stably regardless of the variations of the load.

Abstract: A subsynchronous resonance mitigation system, including a method and apparatus, for damping undesirable subsynchronous resonance oscillations in a generator, which, if left unchecked, may damage the shafts of a turbine-generator set. A remote coupling apparatus, such as a thyristor controlled series capacitor (TCSC) system, a sourced inverter device, or a static phase shifter, is coupled to the generator by a transmission line. In response to a firing command, the coupling apparatus introduces subsynchronous resonance mitigating currents into the transmission line. Sensors monitor power line parameters and/or the generator speed, and in response thereto, a higher-level controller generates a voltage command. A vernier controller responds to the monitored power line parameters and the voltage command to provide the firing command to the coupling apparatus.

Abstract: A microwave oven with a power supply including a transformer having primary and secondary windings, with the primary winding having a plurality of input connections and a secondary winding being coupled to a magnetron. The microwave oven includes a circuit the magnitude of a line voltage supplied to the microwave oven and, in response thereto, for coupling the line voltage to a corresponding one of the input connections to regulate the voltage provided across the secondary winding to the same voltage level regardless of the magnitude of the line voltage.

Abstract: A firing control scheme, including a method and apparatus, for secure vernier operation of a thyristor controlled series capacitor (TCSC) in series with a transmission line uses phase controlled firing based on monitored capacitor voltage and line current. The TCSC system has a thyristor switched inductive commutating circuit in parallel with the series capacitor. Vernier operation of the TCSC system is provided by predicting an upcoming firing angle for switching the commutating circuit to conduct a thyristor bypass current pulse therethrough. The current pulse causes an alternating offset component of voltage to appear across the series capacitor, in addition to the normal voltage component. Each current pulse changes the capacitor voltage proportionally to the integrated value of the current pulse.

Abstract: An optically triggered solid state switch and method for switching a high voltage electrical current. A plurality of solid state switches (350) are connected in series for controlling electrical current flow between a compensation capacitor (112) and ground in a reactive power compensator (50, 50') that monitors the voltage and current flowing through each of three distribution lines (52a, 52b and 52c), which are supplying three-phase power to one or more inductive loads. An optical transmitter (100) controlled by the reactive power compensation system produces light pulses that are conveyed over optical fibers (102) to a switch driver (110') that includes a plurality of series connected optical triger circuits (288). Each of the optical trigger circuits controls a pair of the solid state switches and includes a plurality of series connected resistors (294, 326, 330, and 334) that equalize or balance the potential across the plurality of trigger circuits.

Abstract: A system and method for determining and providing reactive power compensation for an inductive load. A reactive power compensator (50,50') monitors the voltage and current flowing through each of three distribution lines (52a, 52b, 52c), which are supplying three-phase power to one or more inductive loads. Using signals indicative of the current on each of these lines when the voltage waveform on the line crosses zero, the reactive power compensator determines a reactive power compensator capacitance that must be connected to the lines to maintain a desired VAR level, power factor, or line voltage. Alternatively, an operator can manually select a specific capacitance for connection to each line, or the capacitance can be selected based on a time schedule. The reactive power compensator produces control signals, which are coupled through optical fibers (102/106) to a switch driver (110, 110') to select specific compensation capacitors (112) for connections to each line.

Abstract: A PFC controller (FIG. 5) provides power factor correction and peak current limiting for a switch-mode power converter of any topology (buck, boost or buck-boost), without having to directly sense inductor current. The PFC control technique involves using a piecewise-polynomial analog computer (AC) to compute power transistor on-times in accordance with separate polynomial transfer functions for power-factor control and peak-current-linking using as inputs current representations of line input voltage (VLN), load output voltage (VLD), and long-term current demand (VCD). A conduction cycle is initiated by sensing when the rate of change in the inductor current reaches zero using an auxiliary winding on the current storage inductor (Wzd), and terminated after the computed on-time to implement either power-factor control or peak-current-limiting.

Abstract: A gate pulse generator for a reactive power compensation device in which a capacitor is connected in series with antiparallel connected thyristors and which is so constructed that triggering pulses are produced and current is passed into said capacitor when both a signal of forward voltage imposed on said thyristors and a thyristor conduction period signal that is reset by a phase control signal are present. The gate pulse generator includes a means by which conduction period signals associated with thyristors of one polarity are reset during conduction if both a triggering pulse of thyristors of the opposite polarity and a delayed phase control signal associated with the opposite polarity thyristor is present.

Abstract: When there are variations in the short-circuit power of a system, the operating conditions can change, particularly in a controller of a compensating device. To automatically adapt the controller and to avoid or suppress oscillations or voltage variations in the system, a method is provided according to a first solution, where the circuit state of a compensating element is modified for testing purposes. The reaction of the system is detected in a device and, then a parameter which determines the damping of the controller is modified by means of a computing device. According to a second solution, an oscillation of the controller is established by detecting a signal which is dependent on the system voltage and by comparing specific variations. To suppress the oscillations, the hysteresis of the controller is damped by means of the computing device.

Abstract: A static controlled reactance device is inserted in series with an AC electric power transmission line to adjust its transfer impedance. An inductor (reactor) is serially connected with two back-to-back connected thyristors which control the conduction period and hence the effective reactance of the inductor. Additional reactive elements are provided in parallel with the thyristor controlled reactor to filter harmonics and to obtain required range of variable reactance. Alternatively, the static controlled reactance device discussed above may be connected to the secondary winding of a series transformer having its primary winding connected in series to the transmission line. In a three phase transmission system, the controlled reactance device may be connected in delta configuration on the secondary side of the series transformer to eliminate triplen harmonics.

Abstract: A resonant, quasi-square wave, pulse width modulated (PWM) power source (33) for a connectorless power system is disclosed. The power source (33) supplies constant amplitude, fixed-frequency current to a supply loop (31) that is inductively coupled to a plurality of pickup loops (35), each of which supplies power to a remote unit, such as the seat regulator that supplies power to a group of commercial airplane seats (37). Precise, fixed-frequency control is provided by triggering a PWM with fixed-frequency sync pulses. Current control is provided by sensing the current applied to the supply loop, converting the magnitude of the sensed current to a voltage and using the voltage to control the width of the pulses produced by the PWM. The PWM pulses, in turn, control the width of the power pulses applied by the power source (33) to the supply loop (31). Stability and efficiency are improved by maintaining the output of the power source nearly resonant, i.e.

Abstract: The present disclosure describes a method and a system for interconnecting a first and a second three-phase alternating electric networks.

Abstract: In an AC-to-DC converter, a switched inductor, in the form of a ringing-choke or flyback DC-to-DC power converter, is interposed between the AC line input rectifier and the DC storage capacitor. In accordance with the relationship Inductance/Time equals Voltage/Current the inductance and on-time of the switched inductor are held constant so that the instantaneous input voltage and current maintain a directly proportional relationship, thereby imparting a resistive characteristic to the input impedance--i.e., the input reactance vector is held to near zero rotation. Hence, the input power factor is held close to unity. Means are included for varying the values of the inductor and/or time in response to changing load requirements.

Abstract: The system uses a tunable inductor in series with the piezoelectric crystal excitation transducer in the probe which has a flux modulation coil. The bias current through this flux modulation coil is controlled by the system. It is controlled such that the inductance of the tunable inductor cancels out the capacitive reactance of the load impedance presented by the probe when the probe is being driven by a driving signal which matches the mechanical resonance frequency of the probe. The resulting overall load impedance is substantially purely resistive. The system measures the phase angle and monitors the power level. The system uses this information to adjust the bias current flowing through the flux modulation coil to maintain the substantially purely resistive load impedance for changing power levels. This information is also used to adjust the frequency of the driving signal to track changing mechanical resonance conditions for the probe at different power levels.

Abstract: The present invention pertains to a line voltage regulator for a cable which is electrically connected to at least one load. The line voltage regulator includes a device for producing a cable voltage drop signal that corresponds to a voltage drop across the cable which separates the line voltage regulator and the load. The line voltage regulator also includes a sensor circuit for determining distortion voltage across the cable which separates the power supply and the line voltage regulator and the fundamental frequency signal required for regulation. The sensor circuit produces a drive signal that corresponds to the distortion voltage and the fundamental frequency signal required for regulation. Additionally, there is a device for providing voltage to the cable such that the voltage is regulated and distortion voltage across the cable is essentially eliminated as applied to the load. The device for providing voltage is electrically connected to the sensor circuit and controlled by the drive signal therefrom.

Abstract: A voltage-reactive power control apparatus provided together with VAR (volt-ampere reactive) supply equipment at principal points of the power system, such as load area substations. This voltage-reactive power control apparatus monitors the power-flow and load voltage at the load area. The apparatus quickly controls VAR supply equipment etc. upon detecting of voltage abnormalities, information that otherwise would be sent to the control point at a higher level station in the power system upon making decision to provide necessary countermeasures for wider range operation of the power system.

Abstract: In a computer controlled power factor control system switches are activated and deactivated in a predetermined order so that each capacitor is electrically connected to the power distribution system for substantially the same total time throughout the life of the capacitors.

Abstract: A static var compensator which includes a transformer with one end connected to an electric power system and a series circuit constituted by a reactor and a thyristor bulb connected between the other end of the transformer and ground. A voltage detection device detects the voltage of the electric power system and the output of the voltage detection device is sample an even number of times for every cycle of the voltage. A register is provided for storing sampled values an adder is provided for adding absolute values of the sampled values stored in the register. A firing angle of the thyristor bulb is controlled by a control device in accordance with a deviation of an output of the adder from an output of a voltage setting device. A deviation deriving device obtains a deviation of an output of the control device from a predetermined value corresponding to a present var, and an output of the deviation deriving devices is fed back to an input side of the control device.

Abstract: A single stage power conditioner which produces an isolated DC output while drawing resistive input current from the utility has been described. A high frequency switch-mode technique was used which operates in continuous conduction mode to reduce electro-magnetic interference (EMI) generation and ripple losses.

Abstract: A method and apparatus are disclosed for correcting the power factor of an input alternating current signal. The invention is adapted to generating an AC output signal connectable to one or more loads, such as capacitive loads. The circuit includes an energy storage inductor connected in series between the input and output terminals. A short circuit path is provided to connect output terminals during a portion of each half cycle of the AC input voltage waveform. The portion corresponds to the time necessary for the inductor to reach a level substantially corresponding to the peak level of current through the inductor when the short circuit path is disabled. In the preferred embodiment the enablement of the short circuit path between ouput terminals commences at the time the input voltage waveform crosses the zero reference value, and ends at a time at which the AC output voltage exceeds the input voltage.

Abstract: An active filter unit comprising a first active filter which operates under low-frequency PWM control for controlling the fundamental and low-order harmonic capacity and a second active filter which operates under high-frequency PWM control for controlling the high-order harmonic capacity. The first and second active filters are connected in series through associated transformers that are in serial connection across the power lines. The divided filter arrangement reduces the required power rating of high-frequency switching devices.

Abstract: A reactive power compensation device has minimum residual reactive power and avoid hunting. The compensation device is connected to an AC power supply network with a variable reactive load. Capacitor banks are connected in parallel with the load, and a pertinent number of banks are switched on and off periodically at a pre-determined time interval. The reactive power in both the load and the capacitor banks are detected and used for controlling the capacitor banks.

Abstract: A method and capacitor control apparatus for controlling the power factor and voltage on an electrical distribution line based on the power factor on the line subject to a voltage override control. Hysteresis above an undervoltage limit and below an overvoltage limit prevent undesired oscillation in switching the capacitor controls to and from the distribution line.

Abstract: To a static VAR generator of the split reactor type, a scaled down model is associated to be controlled concurrently with the static switches of the split reactor and to generate under proportional line voltage a simulated reactive current which is matched with the actual reactive current to detect a flashover across one of the two halves of the split reactor.

Abstract: In a hybrid switched-capacitor controlled-reactor static VAR compensator including a fixed-capacitor, hysteresis on switching-OFF a switchable capacitor of the capacitance bank is performed with a minimal fixed-hysteresis at the entrance of the standby region and with a temporary and variable-hysteresis in relation to any operating point in the standby region whenever maintaining the capacitor OFF is required. Since the fixed-hysteresis operates most often to prevent switching-OFF of the capacitor while the variable-hysteresis will operate less often, the losses at standby are minimized during thyristor-switched capacitor operation through most of this.

Abstract: An electric locomotive has two AC-DC converters which are connected in cascade, and a power factor controller is connected to one of the converters. Two automatic pulse phase shifters are provided for the two converters and controlled by a signal responding to a difference signal between a current flowing in the converters and a reference signal. One of the input signals of the automatic pulse phase shifter is regulated by a bias signal. The output from each of the automatic pulse phase shifters to each of the converters is switched when the measured speed of the locomotive exceeds a predetermined reference speed signal.

Abstract: In a reactive power compensation apparatus for compensating reactive power generated by a load connected to an AC power supply system, dual phase current signals obtained by dual phase-converting the load currents and unit dual phase voltage signals synchronized with voltages of an AC main line connected to the load are used, and arithmetic operations thereof are performed to separately detect an in-phase reactive component signal and opposite phase component signals of the load currents. Current commands are generated on the basis of the separately detected signals, thereby controlling the reactive power compensation apparatus on the basis of the current commands.

Abstract: The reactive power of an induction machine is compensated by providing fixed capacitors on each phase line for the minimum compensation required, sensing the current on one line at the time its voltage crosses zero to determine the actual compensation required for each phase, and selecting switched capacitors on each line to provide the balance of the compensation required.

Abstract: In an apparatus for controlling the power factor of a power distribution system connected to inductive loads, banks of delta connected capacitors are added to or removed from the power lines of the power distribution system by a plurality of solid state switching devices which are under the control of a microprocessor. The solid state switching devices include optically isolated SCR devices that do not generate electrical interference and provide transient free operation. The microprocessor is also capable of calculating the power factor and displaying it on a digital readout.

Abstract: The present invention pertains to a commutator containing a semiconductor operable with unidirectional current and bidirectional voltage and with controlled interruption and automatic ignition, and in which a semiconductor device with controlled commutation is utilized. In accordance with the invention, the commutator includes a logic gate (61) having an input which, when the anode-to-cathode voltage of the semiconductor device (2) is below a specific positive voltage close to zero, receives a logic signal from an adapting circuit (4) connected to the semiconductor anode. The other input of the logic gate receives a control logic signal, and the output of the gate is connected to another adapting circuit (5) which converts the logic signal output by the logic gate into a suitable control signal which is transmitted to a the control terminal of the semiconductor device (2).

Abstract: In a static VAR generator for providing reactive power compensation to an ac network and including a thyristor-switched capacitor bank having the series combination of a capacitor, a bidirectional thyristor switch having gate drive, and a current limiting inductor with an applied voltage appearing across the combination with a current being conducted therethrough, a damping circuit and method for switching the thyristor switch to achieve damping of oscillatory transients generated by the switching of the capacitor in the network, comprising:determining the magnitude and polarity of a voltage difference .DELTA.

Abstract: The thyristor control pulse generator consists of a dual slope sawtooth signal generator (11, 13, 17) providing a signal U.sub.sy with slopes a and 2a, said sawtooth generator comprising an input (23) for resetting the signal to zero in response to each generated pulse .theta. and means (15) for controlling the switching of the signal slope from value a to value 2a at the time the current in the reactive power regulating inductor becomes cancelled. A comparator (19) compares said signal U.sub.sy to a control voltage U.alpha. to which a correcting signal .DELTA.U.alpha.

Abstract: A method and a system for interconnecting two electrical, alternating three phase networks operating asynchronously or synchronously at voltages of equal or adjacent frequencies, and in which, for corresponding phases, the voltages of the first and second networks are out of phase by a constant or varying angle. A plurality of three phase variable reactive impedances interconnect the two networks for carrying out a desired transfer of active power from one of the two networks to the other. The variable impedances are operated to establish between each phase of the first network and the three phases of the second network, three interconnections each having a different susceptance, which susceptances vary with the three phase variable reactive impedances.

Abstract: Improved control of a var generator of the static type using thyristors wherein control is accomplished by generating a capacitance command representing the value of an equivalent capacitor, as opposed to a current command or a var command. The gating times or angles of the thyristors are determined by the capacitance command acting through an intermediate control which may be an open-loop feed-forward control or a closed loop feedback control operating in response to the difference between the capacitance command and a capacitance feedback, or a combination of both these types of control. The effect of the capacitance control is to provide an improved response of the var generator for changes in source voltage or frequency. The capacitance control also provides an improved linearity of control.

Abstract: A device is taught for controlling the residual charge on a thyristor switched capacitor. A capacitor is in series circuit relationship with at least two bidirectional back-to-back thyristor switches which are then connected across an AC network. Each back-to-back thyristor combination is shunted by a non-linear clamping device which exhibits a very high resistance below a specified voltage level and a very low resistance above that voltage level. A pulse stretcher and a sequential firing circuit arrangement is used to prolong the conduction of one of the thyristor switches at a time to allow the shunting of its associated clamping device. During an overvoltage condition in the AC network, the residual charge on the capacitor will be limited to the breakdown voltage of the conducting clamping device. A plurality of capacitor, thyristor switch, non-linear clamping device combinations may be utilized in parallel with the AC network.

Abstract: A power control apparatus which includes a cycloconverter having thyristors in which a circulating current flows, for supplying a compensating current to AC power lines; capacitors for supplying a reactive current component of the compensating current to the thyristors; a trigger control circuit for controlling the triggering of the thyristors; a detector coupled to the cycloconverter, for detecting from switching currents flowing through the thyristors a circulating signal corresponding to the circulating current. The compensating current serves to improve the power factor of the AC lines as well as to reduce higher harmonic currents on the AC lines. The circulating signal is fed back to the trigger control circuit so that the amount of the circulating current is kept substantially constant according to a negative feedback operation.

Abstract: There is provided by this invention a static VAR generator having an auxiliary shutdown firing pulse generator that initiates a thyristor controlled inductive current to cancel only capacitive current supplied by the static VAR generator in the event of failure of the VAR generator's control means monitoring the capacitive current requirements.

Abstract: A method of, and apparatus for, detecting shorted turns in an electrical reactor. The impedance of the reactor, and its rate of change, are monitored. A reduction in impedance which exceeds a predetermined rate of change indicates the impedance change is due to shorted turns, and not to some normal cause, such as temperature.

Abstract: An automatic var control unit which monitors the reactive volt-amperes of a load on electrical lines, and continuously compensates undesired var by switching onto or from the lines of compensating capacitance. More particularly, the var condition on the electrical lines is sensed, converted into a representative analog voltage, which voltage is then amplified, compared and converted in logic circuits into a first binary pulse representing the need to add/remove capacitance. A flip/flop logic circuit controls by a second binary pulse the addition or removal of capacitance. These binary pulses control the sequencing of relays that perform the actual switching of capacitors in the capacitor bank relative to the electrical lines. The capacitors in the capacitor bank can be switched in series or in binary progression, according to a program in the controller. As a result, the power efficiency of the lines is raised to above 90% by the automatic cancellation of the inductive load reactances.

Abstract: An electronic reactive power regulator is provided for controlling the number of power factor correction capacitors or reactors connected to an electrical power network. A multiplier circuit measures the reactive power in the power network by receiving two input signals which vary in phase angle and amplitude to indicate the amount of reactive power. The multiplier outputs a signal whose DC component indicates the amount of reactive power. This DC component is compared to upper and lower reference limits, and if either of said limits is exceeded, one of two control signals triggers a logic circuit to selectively connect or disconnect the lowest value correction capacitor to the electrical network which is not already connected or disconnected.

Abstract: A circuit for controlling the voltage of a network which supplies electrical power to a load having a rapidly varying impedance. The circuit contains a pair of controlled electric valves which are connected in parallel between two conductors of the network and poled for condition in opposite directions. A voltage transformer produces a signal corresponding to the network voltage, which signal is conducted to an integrator and subsequently compared to a preset mean value. The preset mean value corresponds to a desired amplitude at which the positive and negative half-wave cycles of the network voltage are desired to be maintained. In one embodiment, the controlled electric valves are caused to conduct current during respective half-waves of network voltage so as to maintain the amplitudes of the half-waves at the present mean value. Other features are described for compensating for long term drift of the network voltage and for controlling the controlled electric valves by means of logic circuitry.

Abstract: A discrete-time, closed loop power factor corrector system controls the coupling of a delta-connected switched capacitor array to a 3- or 4-wire power line which may have time-varying, unbalanced, inductive loads. For inductive loads that cannot be exactly compensated with a delta-connected capacitance, the corrector system minimizes the total RMS reactive current drawn from the power line.

Abstract: A VAR generator of the switched capacitor controlled reactor type is shown utilized for a power transmission system. The control arrangement is such that the thyristor controlled capacitor and reactor banks are kept switched out for small terminal voltage variations which can be tolerated without compensation in order to minimize standby or no load losses in the region of the nominal voltage of the transmission system. Outside of this region VAR compensation is provided.

Abstract: This invention discloses a novel means of inserting capacitance into an AC network for power factor correction or voltage regulation that minimizes and transient disturbances to the system. Current surges and voltage transients that are normally associated with connection of capacitors into an AC network is minimized by predetermining an amount of inductance that must be inserted to suppress these transients and simultaneously inserting the inductance into the network with the capacitance.

Abstract: A power factor monitoring and control system with line disturbance immunity for controlling the quality of spot welds made by resistance welding techniques such as those used in the automotive industry on assembly line welders. As is commonly known, quality and strength of a spot weld can be correlated to a change in resistance measured through the weld as the weld progresses during the fusion progress. This change in resistance in the secondary circuit reflects back through the transformer to its primary circuit as a change in power factor. The timing changes resulting from the change in power factor are sensed by the control circuitry of this system to generate signals which are used by an 8-bit microprocessor properly programmed to operate on the signal information. By determining the amount of increase or decrease that has occurred in the current conduction angle during a group of welds, a basis for the control of the welding heat is obtained.