Abstract: The invention relates to an apparatus for ballast weighing on a crane, comprising at least two ballasting cylinders that are equipped to lift/lower the ballast and that each comprise at least one pressure transducer in the region of the piston and/or rod side, and comprising at least one evaluation unit that is equipped to calculate the mass moved by the ballasting cylinders from the pressures detected by the pressure transducers on retraction and/or extension of the ballasting cylinders, excluding the friction forces occurring in the ballasting cylinders. The invention furthermore is directed to a method for calculating the ballast weight of a crane by means of a corresponding apparatus.

Abstract: A melting method including a step of loading solid metal material into an electric furnace, a step of generating an electric arc between at least one electrode and the metal material, a step of perforating the metal material during which the electrode is moved through the metal material, a step of melting the solid metal material in order to obtain a molten material, and a step of refining the molten material by adding reaction compounds. At least one of the steps includes regulating the electric parameters of the electric arc.

Abstract: An electric arc furnace (1) operated with alternating current has a converter (2) which converts mains voltage (U), into primary voltage (U?) having a furnace frequency (f?). A furnace transformer (4) transforms the primary voltage (U?) into a secondary voltage (U?), supplied to electrodes (6) in a furnace vessel (8) (1). They apply electric arcs (10) to a melt material (9) in the vessel (8). The secondary voltage (U?) is also supplied to a capacitor assembly (7) on the output side of the furnace transformer (4) and the furnace transformer (4) is connected on the output side. A control device (5) controls the converter (2) such that a primary voltage (U?) output from the converter (2) to the furnace transformer (4) has a furnace frequency (f) of least ten times the mains frequency (f) and/or greater than 1 kHz.

Abstract: The invention provides a calculation method for operating resistance in a dual-electrode DC electric-smelting furnace for magnesium, including the following steps of: calculating a raw material resistance: simplifying a raw material model as an electrode-centered cylindrical model, determining an electric-field strength of each point in an electric field generated by a raw material layer around an electrode in the cylindrical model, calculating a raw material voltage between two electrodes according to the electric-field strength of each point in the electric field, and further obtaining the raw material resistance between the two electrodes; calculating an electric arc-resistance relation model: determining a relation between an actual electric arc length and a distance from the electrode to a surface of a smelting pool, and calculating a relation between an electric arc voltage and the actual electric arc length, namely the electric arc-resistance relation model; and calculating a smelting pool resistance,

Abstract: A control system for a vacuum arc remelting (VAR) process for a metal includes a direct current (DC) power source, a ram drive, voltage drip short sensor, and a controller, which includes a processor. The drip short sensor may be configured to measure a drip short frequency of the electric arc over a period of time. The controller is configured to determine a real time arc gap length between the electrode tip and the melt pool based on a correlation between the drip short frequency and arc gap length. The controller is further configured to control power input to the electrode by the DC power supply by determining an input power level to input to the electrode based on the real time arc gap length, the input power level configured to generate a desired arc gap length, by the DC power supply, at the input power level.

Abstract: Melting plant having a melting chamber which by way of a gas protection hood is separated from the environment, wherein the gas protection hood or another part of the melting chamber encasement has a lead through in which an electrode rod for moving an electrode to be melted is guided in a gas-tight manner by way of a sealing means. Hydraulic or pneumatic equalisation means, for exerting on the electrode rod equalisation forces which are in a proportional correlation with the gas pressure prevailing within the melting chamber are provided so as to compensate for the gas-pressure forces acting on the electrode rod.

Abstract: An electric arc furnace (EAF) including a raw material container, a set of electrodes, a set of electrical potential transformers, and a reference signal verification device. The set of electrodes are configured to be controllably extended toward the raw material container. The set of electrical potential transformers are correspondingly coupled to the set of electrodes. The reference signal verification device is configured to carry out the steps of reading a reference signal value coming from the raw material container; comparing the reference signal value to an approximated value; and determining that there is a loss of the reference signal if the reference signal value is not within a predetermined amount of the approximated value.

Abstract: A method determines the consumption of electrode material during the operation of an electric furnace, particularly an arc furnace for producing steel. The method determines a weight of an electrode column, which is arranged in the electric furnace or is to be introduced into the electric furnace, using a weighing device. A device for determining the consumption of electrode material of an electric furnace, particularly an arc furnace for producing steel, is provided for performing the method. The device contains a weighing device for determining the weight of at least one electrode column which is arranged in the electric furnace or is to be introduced into the electric furnace, wherein the weighing device is integrated in an operating device of a system containing the electric furnace. Vibration conditions of the electrode column during operation of the electric furnace can also be determined with the method and with the device.

Abstract: During operation of an alternating-current electric arc furnace, which has at least one electrode for producing a melt, vibrations are measured at a wall of a furnace vessel, whereby a slag height of the melt is determined. A rapid reaction to the change in the slag height is made possible by adjusting the arc length of the at least one electrode in the case of deviations of a measured actual value of the slag height from a target value.

Abstract: The invention relates to a method as well as a device for closed-loop control of the electrode gap in a vacuum arc furnace (10), wherein an electrode gap of a melting electrode from the surface of a melt material is subjected to closed-loop control as a function of a droplet short-circuit rate. For this purpose, a histogram (70) of detected droplet short-circuits (80) is created on the basis of at least one droplet short-circuit criterion (76), the histogram (70) is subdivided into sub-areas (72), a characteristic sub-area (74) of the histogram (70) is selected for closed-loop control purposes, and an electrode gap is subjected to closed-loop control on the basis of the droplet short-circuits (80) which can be associated with the selected sub-area (74).

Abstract: An exemplary embodiment includes a method for balancing thyristor bridge circuits, the method comprising, determining currents of thyristors in a first leg of thyristors of a thyristor bridge circuit, determining a first set of gate firing times for the thyristors in the first leg of thyristors responsive to determining the current of the thyristors in the first gate of thyristors, wherein the first set of gate firing times are operative to balance a current load between the thyristors in the first leg of thyristors, and gating the thyristors in the first leg of thyristors according to the first set of gate firing times.

Abstract: Embodiments of a system for controlling the position of an electrode in an arc furnace comprise an arc furnace comprising a molten bath and slag disposed over the molten bath, wherein the slag contacts the molten bath at an interface. The system further comprises an electrode comprising a lower tip, wherein the electrode is configured to deliver current by disposing the lower tip of the electrode below the upper surface of the slag. The current is substantially directed through the slag to the interface. The system also comprises a control system configured to determine the position of the lower tip of the electrode relative to the upper surface of the slag based on harmonic frequencies associated with the current, wherein the lower tip position relative to the upper surface of the slag correlates to the harmonic frequencies.

Abstract: A furnace's operating efficiency is improved by simultaneously monitoring various furnace operating parameters such that the monitored values may be collectively examined and correlated to determine if the furnace is sub optimally operating. In particular, the electrode current, hydraulic valve spool position, hydraulic fluid pressure, and electrode mast position of an electrical arc furnace are simultaneously monitored and correlated to determine if any unidentified sub optimal operating conditions are present. By improving the chances of detecting and correcting sub optimal operating conditions, the present invention improves the electrode consumption and overall efficiency of a furnace's operation.

Abstract: A method and system for stabilizing energy consumption in multiple loads, or in single multi-phase loads. The method and system also compensates for unbalance in multi-phase loads. A central controller monitors variable reactances in the loads and identifies situations of power and/or current fluctuation and/or unbalance. It determines appropriate corrective action by the other loads/phases to compensate for the power and/or current change or unbalance due to the problematic load, and it issues control signals instructing variable reactor controllers associated with the other loads to adjust accordingly. The method and system may by applied to electric arc furnace installations. The system and method may be employed to maintain a predetermined level of unbalance in the system.

Abstract: A method and system for stabilizing energy consumption in multiple loads, or in single multi-phase loads. The method and system also compensates for unbalance in multi-phase loads. A central controller monitors variable reactances in the loads and identifies situations of power and/or current fluctuation and/or unbalance. It determines appropriate corrective action by the other loads/phases to compensate for the power and/or current change or unbalance due to the problematic load, and it issues control signals instructing variable reactor controllers associated with the other loads to adjust accordingly. The method and system may by applied to electric arc furnace installations. In this context, the method and system provide an electrode position controller coupled to the feed rate controller so as to predictively anticipate the introduction of new source material and lower the electrodes so as to prevent arc extinguishment while the variable reactors maintain predetermined power set-points.

Abstract: An apparatus and method for controlling an electroslag remelting furnace comprising adjusting electrode drive speed by an amount proportional to a difference between a metric of electrode immersion and a set point, monitoring impedance or voltage, and calculating the metric of electrode immersion depth based upon a predetermined characterization of electrode immersion depth as a function of impedance or voltage.

Abstract: The electrode arrangement uses vertically oriented electrodes with side wall contacts for an electrothermic smelting furnace for aluminum production. The side wall contacts are radially moveable into the furnace to compensate for wear on the contacts. The side wall contacts can be hollow to allow a slag forming charge to be fed to the furnace.

Abstract: A method for the continuous determination of the distance between an electrode tip and level of a bath in an electric arc furnace so as to be able to exactly determine electric energy consumption per tonne of scrap actually melted, electrode wear and the residual liquid bath present in the electric arc furnace after tapping.

Abstract: A power control system for an AC electric arc furnace. The control system includes variable reactors located intermediate a furnace power supply and arc electrodes that are height adjustable. The control system monitors operating characteristics of the furnace that are indicative of the active power consumption of the furnace and adjusts the variable reactors and the electrode height so as to minimize variations in the active power consumption. Loss of electrode arc can be predicted and countered by lowering the electrodes and decreasing the reactance of the variable reactors.

Abstract: A power control system for an AC electric arc furnace. The control system includes variable reactors located intermediate a furnace power supply and arc electrodes that are height adjustable. The control system monitors operating characteristics of the furnace that are indicative of the active power consumption of the furnace and adjusts the variable reactors and the electrode height so as to minimize variations in the active power consumption. Loss of electrode arc can be predicted and countered by lowering the electrodes and decreasing the reactance of the variable reactors.

Abstract: A method of and apparatus for controlling an electroslag remelting furnace by driving the electrode at a nominal speed based upon melting rate and geometry while making minor proportional adjustments based on a measured metric of the electrode immersion depth. Electrode drive speed is increased if a measured metric of electrode immersion depth differs from a set point by a predetermined amount, indicating that the tip is too close to the surface of a slag pool. Impedance spikes are monitored to adjust the set point for the metric of electrode immersion depth based upon one or more properties of the impedance spikes.

Abstract: A method of and apparatus for controlling an electroslag remelting furnace by driving the electrode at a nominal speed based upon melting rate and geometry while making minor proportional adjustments based on a measured metric of the electrode immersion depth. Electrode drive speed is increased if a measured metric of electrode immersion depth differs from a set point by a predetermined amount, indicating that the tip is too close to the surface of a slag pool. Impedance spikes are monitored to adjust the set point for the metric of electrode immersion depth based upon one or more properties of the impedance spikes.

Abstract: A power control system for an AC electric arc furnace. The control system includes variable reactors located intermediate a furnace power supply and arc electrodes that are height adjustable. The control system monitors operating characteristics of the furnace that are indicative of the active power consumption of the furnace and adjusts the variable reactors and the electrode height so as to minimize variations in the active power consumption.

Abstract: Disclosed is an electrode control system for an electric arc furnace having a furnace transformer. The electrode control system includes a current transformer for measuring operating current of the electrode and a voltage transformer for measuring operating voltage of the electrode. An active power transducer is connected to the current transformer and the voltage transformer for calculating active power of the electrode from the measured operating current and operating voltage as a first output signal. A reactive power transducer is connected to the current transformer and the voltage transformer for calculating the reactive power of the electrode from the measured operating current and operating voltage as a second output signal. A programmable control unit is connected to the active power transducer and the reactive transducer for receiving the first and second input signals.

Abstract: The present invention relates to a method for weighing an electrode submerged in the charge of an electric smelting furnace. The electrode is moved in vertical direction at least once, whereafter the electrode is lifted and the weight of the electrode is registered shortly after the electrode has been lifted.

Abstract: The present invention relates to a method for determination of the electrode tip position for consumable electrodes in electric smelting furnaces, which electrodes being submerged in the furnace charge. The voltage between two geometrically displaced points on the outside of the steel wall of the furnace pot is measured during operation of the furnace, points being situated as close as possible to the electrode for which the electrode tip position is to be determined, and as far away as possible from the other electrodes in the furnace. The electrode current for the electrode for which the electrode tip position is to be determined, is recorded at the same time as the voltage between the two points are measured, whereafter the difference between measured voltage between the two points and measured electrode current is calculated, and where the absolute value of difference increases when the electrode tip position increases and decreases when the absolute value of difference decreases.

Abstract: An apparatus and method of controlling a remelting process by providing measured process variable values to a process controller; estimating process variable values using a process model of a remelting process; and outputting estimated process variable values from the process controller. Feedback and feedforward control devices receive the estimated process variable values and adjust inputs to the remelting process. Electrode weight, electrode mass, electrode gap, process current, process voltage, electrode position, electrode temperature, electrode thermal boundary layer thickness, electrode velocity, electrode acceleration, slag temperature, melting efficiency, cooling water temperature, cooling water flow rate, crucible temperature profile, slag skin temperature, and/or drip short events are employed, as are parameters representing physical constraints of electroslag remelting or vacuum arc remelting, as applicable.

Abstract: An arrangement and method for determining the height position of a vertically movable electrode (2) in an arc furnace (1). The arrangement includes an elongated, flexible element (9), preferably a heavy chain, whose one end is attached to a first attachment point on the movable electrode (2). The other end of the chain is attached to a fixed second attachment point. The total weight of those flexible element parts that are carried by the movable and the fixed attachment points respectively will vary in response to vertical movement of the electrode. The arrangement also includes load cell for sensing the part of the total weight supported by the fixed attachment point, for determining the height position of the electrode (2).

Abstract: An arc control apparatus for a DC arc furnace provides an additional magnetic field which prevents a discharged arc from shifting outward at an arc generating point due to the influences of a magnetic field generated by a feeder circuit, thus directing the arc discharge vertically downward. The arc control apparatus includes an arc furnace in which an object to be melted is disposed. A movable electrode is disposed in the arc furnace for movement relative to the object. A feeder circuit including a power supply and a feeding conductor is connected to the movable electrode and the arc furnace for supplying a voltage therebetween from the power supply through the feeding conductor to generate an arc whereby the object is dissolved. An auxiliary coil is disposed outside and in the vicinity of the arc furnace and connected to the feeder circuit for generating a counter magnetic field in a direction to cancel a magnetic field which is generated at a point of generation of the arc by means of the feeder circuit.

Abstract: A method and apparatus for controlling vacuum arc remelting (VAR) furnaces by estimation of electrode gap based on a plurality of secondary estimates derived from furnace outputs. The estimation is preferably performed by Kalman filter. Adaptive gain techniques may be employed, as well as detection of process anomalies such as glows.

Abstract: An apparatus and method for controlling an electroslag remelting furnace, imposing a periodic fluctuation on electrode drive speed and thereby generating a predictable voltage swing signal. The fluctuation is preferably done by imposition of a sine, square, or sawtooth wave on the drive dc offset signal.

Abstract: A secondary circuit having a variable impedance for electric arc furnaces of a type working with alternating current, which is associated with a transformer (11) is disclosed. A secondary circuit comprises at least one rigid connection (12) connected to the outputs (16) of the transformer (11), flexible cables (13) connected through rigid connection elements (29, 129) at first end to the rigid connection (12) and at the other end to specific electrodes (15). At least one branch of the secondary circuit (10) corresponds to a specific phase including at least one of the respective rigid components (12, 17, 29, 129) having at least two parts reciprocally positionable in an adjustable manner according to the required value of overall reactance of the specific branch of the secondary circuit (10) comprising that rigid component (12, 17, 29, 129).

Abstract: The electrode gap of a VAR is monitored by determining the skewness of a distribution of gap voltage measurements. A decrease in skewness indicates an increase in gap and may be used to control the gap.

Abstract: A process and a device for regulating the position of the tip of an electrode immersed in an electric furnace heated by electric arc or resistance heating. To precisely measure the position of the electrode tip and to position it in operation, a series of gas containers are introduced into the electrode in succession at certain intervals, with each gas container being given a serial number (n.sub.i). The position of the electrode tip is determined by computer from the data of the last gas container with the serial number (n.sub.j) and the current number of the melted-open gas container, determined by gas analysis, using the gas that rises in the furnace through the melting process. Control technology is then applied to the drive of the electrode bearing device.

Abstract: During operation, DC arc furnaces (8) produce undesired reactive load fluctuations which are compensated by means of a power factor compensator (31). An AC power controller (28) of the power factor compensator (31) is controlled as a function of a stabilization striking angle signal (.alpha..sub.st) which is controlled in accordance with the reactive power of filter branches (4, 4') by a function generator (26) as a function of a desired reactive power signal (Q.sub.des8), of a reactive power actual value signal (Q.sub.8) of the arc furnace (8) and of a filter reactive power signal (Q.sub.F). The desired reactive power signal (Q.sub.des8) is formed by means of a phase-angle controller (35) as a function of a total current intensity (i.sub.33) which, in addition to the current actual value (i.sub.act) of the arc furnace (8) also comprises the current of the filter branches (4, 4') and that of any auxiliaries.

Abstract: A system for controlling electrode gap in an electro-slag remelt furnace has a constant regulated voltage and an eletrode which is fed into the slag pool at a constant rate. The impedance of the circuit through the slag pool is directly proportional to the gap distance. Because of the constant voltage, the system current changes are inversely proportional to changes in gap. This negative feedback causes the gap to remain stable.

Abstract: Apparatus and method for obtaining accurate sonic input data from a metallurgical furnace, for accomplishing accurate control of a lance injecting oxygen and/or other substances into the melt. A remotely located hydrophone is placed in sonic communication with a liquid circuit cooling the lance. Sound levels and frequencies are picked up through the liquid, and transmitted to a programmable logic controller which generates control signals operating the lance. An associated real time analyzer compares the sonic signature of the input data to predetermined sonic signature data retained in memory, and adjusts lance operation through the programmable logic controller accordingly in order to operate the furnace optimally. Sonic transmission is more accurate, and the hydrophone is more protected from the harsh furnace environment due to its remote location and employment of liquid sound transmission, when compared to other microphone arrangements.

Abstract: An electric arc furnace includes at least one electrode projecting into a furnace vessel for containing a charge to be heated and electrode support structure for moving the electrode in a direction along a path towards and away from the charge. An improvement to the electric arc furnace comprises a sensor for detecting the position of the electrode support structure from an initial position. A processor calculates one of a support structure travel distance from the initial position and a rate of electrode consumption. An alarm signal is generated in response to at least one of the travel distance and the rate of electrode consumption being at least equal to a respective predetermined threshold travel distance or a predetermined threshold rate of electrode consumption, either of which is indicative of an excess electrode consumption condition for a given heat.

Abstract: DC arc furnaces have a current regulator for maintaining the current of an arc constant and an electrode regulator for affecting the position of an electrode of the arc furnace and thus the length of the are. Adjustment of the position of the electrode takes place by a hydraulic electrode adjustment device, which is controlled as a function of the difference between a predeterminable electrode regulator command variable signal and a voltage actual signal. The arc length is adjusted in such a way that a rectifier operates on the average with a deflection of, for example, 35.degree. el., independently of the secondary voltage of a furnace transformer and a set current set value. To be able to better protect the wall of the arc furnace and to better utilize the fed-in energy during operation with foaming slag, the arc length is automatically adapted to a slag height.

Abstract: The invention relates to an electrode system for melting and stirring and also for temperature control in metallurgical vessels. To achieve optimum energy utilization with minimal gas consumption, the electrode system comprises, according to the invention, a central electrode and an outer electrode (10, 11) which are each attached to a height adjustment (12) and are connected to a common electric power source (16), to form an electric arc between central electrode and melt below the surface of the melt bath, and an annular space (23) between central electrode and outer electrode (10, 11), which is connected to a gas source (25), with the gas system being designed in such a way that finely particulate additives can also be charged into the melt.

Abstract: According to the present invention, there is provided a direct current electric furnace for melting metal capable of melting scraps rapidly and also capable of diminishing cold and hot spots formed on the furnace wall, wherein the direct current electric furnace is provided with a single top electrode, a plurality of furnace bottom electrodes, or a plurality of electrode units obtained by dividing a multitude of furnace bottom electrodes of a small diameter into plural units, and electric current controlling thyristor circuits for controlling each individually electric currents flowing through the plural furnace bottom electrodes or electrode units. The electric current controlling thyristor circuits may be substituted by thyristor circuits for controlling electric currents for each of plural groups obtained by dividing the above plural furnace bottom electrodes or the above many furnace bottom electrodes or the above plural electrode units into the plural groups.

Abstract: An improved arc furnace regulator employs neural circuits connected in a multi-layer network configuration with various weighted relationships between the successive layers which are automatically changed over time as a function of an error signal by means of the back-propagation method so that the regulator gradually improves its control algorithm as a result of accumulated experience. The network is implemented in software which can be developed and run on a PC with extra co-computing capability for greater execution speed. A second trainable neural network which emulates the arc furnace is used to develop the error signal, and is trained in mutually exclusive time periods with the training of the regular network.

Abstract: Direct current arc furnaces (8) have a current regulator (14) for maintaining the current of an arc (10) constant, and an electrode control (18) for affecting the position of an electrode (7) of the arc furnace (8) and thus the length of an arc (10). Control of the position of the electrode (7) is effected by means of a hydraulic electrode adjustment device (21), which is controlled as a function of the difference between a predeterminable electrode control input signal (.alpha..sub.soll) and an actual rectifier value signal (.alpha..sub.ist) at the output of the current regulator (14). In this way the length of the arc is controlled in such a way that a rectifier (5) operates with a mean control of, for example, 25.degree. el., independent of the secondary voltage of a furnace transformer (2) and of a set current reference value (i.sub.soll).

Abstract: Method and apparatus for controlling electrode immersion depth in an electroslag remelting furnace. The phase difference of the alternating current circuit established in the furnace is calculated in real time and employed to more accurately control immersion depth than possible with voltage-swing systems.

Abstract: Method and device to control the force applied to the electrode-bearing arms of an electric arc furnace, the vertical regulation of the electrodes being achieved with an electrohydraulic or electropneumatic system consisting of an operational cylinder actuated by a fluid under pressure so as to raise and lower the electrodes, the control means of the system being adjustable by means of an electrical device, whereby the working pressure of the operational cylinder is measured by a pressure transducer (15) and is processed by a processor system (16) so as to obtain the weight of the electrodes and the condition of static pressure, the processor system (16) governing a quick-response servovalve (18) and being governed by an interface (19) of the system that adjusts the electrical current fed to the electrodes (11).

Abstract: A feedback control system for the impedance control of an electric arc furnace having at least one electrode, a hydraulic electrode actuator for adjusting the electrode. The actuator is adapted to be supplied with hydraulic fluid through a control valve. The furnace further includes a controller, which is connected to the valve actuator for the control valve, and impedance signal generator for delivering impedance signals to one input of the controller and a setpoint signal generator for delivering a setpoint signal representing a desired impedance to another input of the controller.

Abstract: Method to feed a three-phase direct-arc electric furnace with controlled current and also a three-phase electric furnace thus fed for the smelting of metals, e.g.

Abstract: An improved arc furnace regulator employs neural circuits connected in a multi-layer network configuration with various weighted relationships between the successive layers which are automatically changed over time as a function of an error signal by means of the back-propagation method so that the regulator gradually improves its control algorithm as a result of accumulated experience. The network is implemented in software which can be developed and run on a PC with extra co-computing capability for greater execution speed. A second trainable neural network which emulates the arc furnace is used to develop the error signal, and is trained in mutually exclusive time periods with the training of the regular network.

Abstract: The invention provides a direct current electric arc furnace which is composed of a feeding system of direct current to the furnace, a movable electrode at the roof of the furnace, and a bottom electrode attached to the bottom of the furnace at the position deviated from the center of the bottom of the furnace, the deviated distance from the center being determined by a magnetic field, generated by a current in the steel bath of the furnace, from under an arc generated by the movable electrode to the bottom electrode, which can cancel a second magnetic field generated by the current of the feeding system.

Abstract: A flicker compensating apparatus for compensating for flickering due to a variation in the reactive power generated from a DC arc furnace connected by an AC/DC converter to an AC power system, comprises: a current detector for detecting a DC current flowing in the DC arc furnace; a controller for determining the phase control angle of a thyristor included in the AC/DC converter in accordance with the difference between the detected DC current and a predetermined reference current; a calculator for calculating reactive power to be generated by the DC arc furnace, from the detected DC current, the determined phase control angle, and a no-load DC voltage; a compensator including a reactive load connected via thyristor to the power system; and a controller for controlling the phase control angle of the thyristor of the compensator in accordance with the calculated reactive power, for controlling a current flowing across the reactive load, and for permitting the compensator to generate such reactive power as to co