SU548930A1 - Converter of multiphase ac voltage into direct current - Google Patents

Description

Three-phase AC to DC converters are known that contain a semi-controlled valve bridge, at which the common point of connection of the valves of the uncontrolled (for example, anode) group is directly connected to one of the output pins. Such converters also contain auxiliary valves and a capacitor. Due to the presence in the conversion circuit of a series-connected capacitor, the power transferred to the load is limited so that the converter is operational at any value up to a short circuit in the load. Such a property is especially valuable, for example, for ion nitriding furnaces for parts.

However, a large number of valves in the conversion circuit, connected in series at any time, impair the converter’s energy performance and complicate its design.

The proposed converter differs from the known ones in that the phase outputs of the bridge are connected to the common point through auxiliary thyristors, which through the capacitor is connected to the common connection point of the valves of the controlled group (cathode, for example), and the plates of this capacitor are connected to another output terminal conclusion.

This simplifies the device and increases its efficiency.

On f {{g. 1 is a circuit diagram of a converter; in fig. 2 - timing diagrams illustrating the operation of the device with an active load.

Claims (1)

The device is a bridge converter, the anodic group of valves of which, for example, for the semi-controlled converter, is made on diodes 1, 2, 3, and cathodic - on thyristors 4, 5, 6. Phase outputs of the bridge through auxiliary thyristors 7, 8, 9 united in a common point, which through the capacitor 10 is connected to the common connection point of thyristors 4, 5, 6. The plates of the capacitor 10 through the thyristors I, 12 connect H1 1 to the output terminal 13 of the converter. Its other pin 14 is formed by a point, combining diodes 1, 2, 3. The load of the converter is resistance 15. The device operates as follows. Suppose at time to include thyristors 4, 12 and capacitor 10 pre-charged to the line voltage of the previous interval with polarity shown in FIG. 1, is recharged along the formed circuit: the positive pole of the capacitor 10, the thyristor 12, the load 15, the diode 2, the power source in the form of a linear EMF U, the thyristor 4, the negative pole of the capacitor. At the same time, a voltage pulse is formed on the load, the shape of which depends on the parameters of the converter and the load, and the energy in the pulse is constant and equal (for the case of the active load or load, shunted by a reverse diode): W 2C-U. By the time t, the capacitor 10 recharges to reverse voltage. At time tj, tupHCTopbi 7, 11 is turned on, and a specified amount of energy is transferred to the load. At the same time, the reverse voltage of the capacitor 10 is applied to the thyristors 4, 12 for the time required to restore their control capacity. At time tj, the thyristors 4, 12 are connected again, the opposite voltage is applied to the thyristors 7, 11, and a predetermined amount of energy is transferred to the load again. Thus, the converter operates during the entire time interval while the voltage of the phase a exceeds the voltage of the remaining phases. If the voltage of the phase at the time t becomes greater than the voltage of the phases and and c, then include a pair of thyristors 5, 12 or 8, 11 depending on the polarity of the voltage on the capacitor 10 by this time. Thyristors 5, 8 together with thyristors 11, 12 work during the entire time interval, while the voltage of phase exceeds the voltage of phases a and c. Similarly, in the interval when the voltage of the phase c is the most positive, the thyristors 6, 9 work in conjunction with thyristors P, 12. By adjusting the capacitor overcharging frequency, you can adjust the average value of the energy in the load with a good cosi converter relative to the network, because the angles of the shoulders control when adjusting, the converter remains zero. The property of invertibility of this converter should be noted. In the case of a motor load, if it is necessary to ensure the 1 вер вер rotary mode in this converter, it is sufficient to replace the diodes 1, 2, 3 with three controlled valves. The control of these valves in this case 4 exists as in a conventional inverter. The adjustment angles are close to 180 e. hail. The regulation of the mean value of the roto-emf of the inverter is carried out by the same tool as in the rectifier mode described above. Note also that this scheme has a wide range of control options. Thus, if in addition to the frequency control of the medium voltage, the switching angles of the thyristors of the converter's shoulders are adjusted, which corresponds to the control of the controlled valves in the usual driven converters, it is possible to carry out the amplitude control of the voltage and load pulses. In addition, this converter can operate in the normal mode of inversion or inversion. In this case, the capacitor 10 serves only to accelerate the disconnection of the load in the event of an accident (short circuit of the load). In the operation mode of the converter with a capacitor in the recharge circuit, it is easy to protect the converter in the case of the sec. loads by a simple and well-known means by removing control pulses, and in any case, in particular, as K. loads, as already noted, the energy transferred to the load is strictly limited, which is a necessary requirement for a number of loads. For example, for ion nitriding furnaces, the energy transferred to the load may be limited at a level that will prevent damage to the workpiece as a result of the arc discharge. Along with a smaller number of serially connected valves in the transforming path in comparison with the prototype, the average current through thyristors 4–9 is equal to half the average value of the current of the bridge valves in the prototype, which makes it possible to reduce the number of current drives used. Claims A multiphase AC voltage to DC converter containing a semi-controlled valve bridge, the common connection point of the uncontrolled valve of which is directly connected to one of the output pins, as well as auxiliary valves and a capacitor, characterized in that, in order to simplify raising the main power supply line, the phase outputs of the bridge through the auxiliary thyristors are connected to a common point connected through a capacitor to the common connection point of the valves of the controlled group, and the plates of this condensers through other complement (shtelnye thyristors connected to another output vyvotsu. --T  Os o but j S / T, -0/4 J / 3 f ./v 2 rig. 2