SU733092A1 - Low-frequency generator for supplying electrospark machines - Google Patents

Description

The invention relates to the impulse technique, namely the electric impulse processing of metals. Known low-frequency generators for powering EDM machines. One of the known low-frequency generators contains a controlled rectifier made on a three-phase bridge circuit on thyristors, and a control system for this rectifier 1. However, the absence of a specific rectifier control circuit does not allow us to determine how the frequency range from 1 to 300 Hz is obtained. The closest technical solution to the dainom invention is a low-frequency generator for powering EDM machines, containing a multiphase rectifier circuit on unmanaged vents and thyristors, shunted by resistors, and a thyristor control unit, which includes a frequency division device, a phase-mixing device, a blocking device generator and short circuit cancellation unit 2. The disadvantage of such a generator is the lack of synchronization of the duration and duty cycle of output pulses with the network n a frequency below 50 Hz. The purpose of the invention is to improve the synchronization accuracy. This goal is achieved by the fact that a low-frequency generator for powering EDM machines contains a three-phase power transformer, the inputs of which are connected to a three-phase voltage network, and the outputs are connected to the inputs of a controlled rectifier made on thyristors, the control inputs of which are connected to the outputs of the output converter devices and the outputs are connected to the EDM busbars and the inputs of the short-circuit protection device, the output of which is connected to the first input of the control unit, a low voltage generator whose inputs are connected to a three-phase voltage network, and an output connected to the second input of the control unit; a phase shifter whose inputs are connected to the first outputs of the control unit; and a modulator whose output is connected to the third input of the control unit. the outputs of which are connected to the fourth inputs of the control unit.

one input is connected to the output of the phase shifter, and the second inputs are connected to the auxiliary outputs of the synchronizer, an address pulses switch, the outputs of which are connected to the inputs of the output device, and control inputs are connected to the second outputs of the control unit, and an address pulse generator, whose outputs are connected to signal the switch inputs of the address pulses, and the inputs are connected to the signal outputs of the synchronizer.

FIG. Figure 1 shows a structural electrical circuit for a low-frequency generator for powering an EDM machine; in fig. 2 - voltage diagrams for the operation of the low-frequency generator in the initial state; in fig. 3 - voltage diagrams for the operation of a low-frequency generator at a frequency of 300 Hz; in fig. 4 and 5 are voltage diagrams for the operation of a low-frequency generator at a frequency of 150 Hz; in fig. 6 shows voltage diagrams for the operation of a low-frequency generator at a frequency of 30 Hz.

A low-frequency generator for electrical erosion machines consists of a three-phase power transformer 1, a controlled rectifier 2, made on a three-phase bridge circuit on thyristors, resistor-connected, whose input is connected to a power transformer 1, and the output of IK to the electroerosion gap 3, shunted by a resistor, and the system control, which includes the synchronizer 4, the driver 5 address pulses, the switch 6 address pulses, the output device 7, the phase shifter 8, the driver 9 time intervals, control unit 10, short circuit protection device 11 and modulator 12

The control unit 10 consists of an operation mode switch 13, a NO element 14, an NAND element 15, a control relay 16 having contacts 17-19, a protection relay 20 having contacts 21 and 22, and the Start and Stop buttons.

The low-frequency generator generates a range of frequencies from 300 Hz and below, which is determined by the formula.

where f is the limiting frequency,.

fn 300 Hz;

in is the natural number of numbers 1,2,3,4,5 ..., then the number of frequencies that the generator generates will be 300, 150, 100, 75, 60, 60 ...

Depending on the frequency of the pulses at the EDM gap, the low-frequency generator operates in three modes. In the first mode, the low-frequency generator generates pulses with a frequency of 300 Hz, during

the second mode - the frequency of 150 Hz, and in the third mode - a frequency of 100 Hz and below.

The mode of operation is selected by switch 13, which has three four-pole fields. The first contact field 131 switches the inputs of the phase shifter 8, the second contact field 13g switches the outputs of the phase shifter 8, the second contact field 13g switches the outputs of the phase shifter 8 and the time interval generator 9, and the third contact field 13z switches the control inputs of the switch 6 address pulses.

Phase shifting device 8 operates in two modes. When the low-frequency generator operates at a frequency of more than 100 Hz, the phase-shifting device 8 operates in the mode when the time interval at its output is commensurate with the period of the clock pulses (Fig. 2d). In this mode, the phase-shifting device 8 performs a smooth control of the conduction angle of the thyristors of the controlled rectifier 2 in the range from O to d / 3. When the low-frequency generator operates at a frequency of 100 Hz and below, the phase shifter 8 operates in the mode when the time interval is longer than the sync pulse period (Fig. 2d). In this mode, the phase-shifting device 8 simultaneously performs both smooth adjustment of the conduction angle of the thyristors of the controlled rectifier 2 in the range from O to l / 3, and discrete adjustment of the conduction angle of these thyristors multiple of l / 3.

The imaging unit 9 of the time interval selects a base time interval equal to l / 3.

The operation of the low-frequency generator in the initial state is illustrated by the voltage diagrams shown in FIG. 2. The synchronizer 4 generates, at times corresponding to the intersection points of the phase voltage curves (Fig. 2a), short duration address pulses (Fig. 26). The address pulses are fed to the input of the imager 5, which generates address pulses (Fig. 2c) with a duration equal to the conduction angle of each thyristor of the bridge circuit of the controlled rectifier 2, which is equal to 1/3 of the period of the three-phase voltage network, i.e. equal to 2n / 3. Address pulses of duration equal to 2l / 3 enter the switch 6.

Synchronizer 4 generates short pulses (Fig. 2d) with a frequency of 300 Hz and pulses (Fig. 2e, e) with a frequency of 150 Hz and a duration of l / 3.

Claims (2)

As long as the control relay 16 is de-energized, its closing contact 19 is open and the 300 Hz clock pulses do not arrive at the input of the phase shifter 8. The output of the phase shifter 8 and, consequently, at the output of the driver 9, the control signal is absent. The absence of a signal to the control inputs of the switch 6 does not allow receiving address pulses at the outputs of switch b; therefore, the thyristors of the controlled rectifier 2 are locked and electroerosive processing of metals does not occur. The operation of the low-frequency generator at a frequency of 300 Hz is carried out by setting the switch 13 to the operation mode of the control unit 10 to the "300 Hz" position and then pressing the Start button. The control relay 16 is activated and the closing contact 17 shunts the Start button, thus becoming the self-powered control relay 16, the signal "Setting O from the phase shifter 8 is disconnected by contact 18, and the contact clock of the clock pulses is closed by the closing contact 19 (Fig. 2d ) from the synchronizer 4 to the corresponding input of the phase-shifting device 8. At the output of the phase-shifting device 8, pulses appear (Fig. 36), which through the contact field 132 of the operating mode switch 13 and the element 14 do NOT flow to the first input Dr. element 15 and NOR. To the second input of the element 15 I-NOT through the button "Stop and contact 17 of the control relay 16" a constant signal is given, which is present during the entire operation of the low-frequency thyristor. The third input element 15 AND-NOT receives a signal from the device 11 protection, when there is no short circuit of the electroerosive gap. High-frequency memory pulses from the modulator output, 12, are supplied to the fourth input of the 15 NAND element. 12. Pulses (FIG. 36) from the output of the 15 NIP element arrive through the contact field 13 of the operating mode switch 13 to the corresponding control input of the 6 address pulses . At a frequency of 300 Hz, the address pulses have a sequence that is shown in FIG. Pros: These address pulses are gated with signals (FIG. 36), with the result that at the output of switch 6, the address pulses take on the form shown in FIG. Sound The address pulses (Fig. 3a), amplified by the output device 7, arrive at the control electrodes of the thyristors of the controlled rectifier 2 at the moments when the direct voltage is applied to the thyristors. Two thyristors work simultaneously in controlled rectifier 2: one in the anode group and the other in the cathode group. The electroerosive gap at any time is connected to two phases of the secondary winding of a power transformer 1. The operation of the control rectifier is illustrated by diagrams of instantaneous values of phase voltages (Fig. 3g) on the thyristors, and the voltage on the electroerosion gap at idle of the low-frequency generator is shown in FIG. 3d. In the event of a short circuit of the electroerosion gap at the output of the protection device 11, a zero signal appears, which prohibits the signal from the output of the phase shifting device 8 to the control input of the switch 6 of address pulses. The occurrence of a zero signal triggers the protection relay 20, which opens the input circuit of the phase shifter 8 with its contact 21, and contacts the phase shifter 8 of the initial state with contact 22. The low-frequency generator assumes a state that lasts until the short circuit of the EDM gap is eliminated. As soon as the short circuit is eliminated, the voltage goes to the EDM gap 3 through resistors bypassing the thyristors of the controlled rectifier 2. A single signal appears at the output of the protection device 11. The protection relay 20 is de-energized and its contacts 21 and 22 accept the states indicated in FIG. 1. The low-frequency generator automatically goes into operation. The transfer of the low-frequency generator from the operating state to the initial state is carried out by pressing the button "Stop. The control relay 16 is de-energized and its contacts 17-19 receive the states indicated in FIG. 1. When the Stop button returns to its initial position, the control relay 16 remains in a de-energized state. The operation of the low-frequency generator at a frequency of 15 Hz is divided into two ranges. This is because the range of adjustment of the conduction angle of the thyristors of the controlled rectifier 2 is 2L / 3, whereas the smooth control by the phase shifter 8 of the conduction angle is only / 3. The operation of the low-frequency generator in the range shown in FIG. 1 is explained in the voltage diagrams shown in FIG. 4, and its operation in a different range is explained by the voltage diagrams shown in FIG. 5. The operation of the low-frequency generator in each of the considered ranges is identical and differs only in the length of the time interval (Fig. 46 and Fig. 5a) at the output of the imaging unit 9. Phase-shifting device 8 operates in the same mode as at 300 Hz. The output pulses from the phase shifting device 8 are fed to the input of the imaging unit 9, where they are formed by the pulses (Fig. 2e, e) into the pulses shown in Figs. 46 (Fig. 5a), which are then output from the imaging unit 9 through the contact field 13 of the operation mode switch 13, NOT element 14, the AND-N 15 element and the contact field 13 of the switch 13 to the corresponding control input of the switch 6. Address pulses (FIG 4a) gates pulses (Fig. 46 or Fig. 5a), obtained at the output of the imaging unit 9. Address pulses (Fig. 4c or Fig. 56), amplified by the output device 7, are applied to the control electrodes of the thyristors of the controlled rectifier 2 The operation of the controlled rectifier 2 is illustrated in the diagram and the instantaneous values of the phase voltages to the thyristors shown in FIG. 4d (fig. 5c), and in fig. 4d (Fig. 5d) shows voltage curves on the EDM gap when idling. The operation of the low-frequency generator at a frequency of 100 Hz and below differs from the operation of this generator at frequencies above 100 Hz in that the phase shifter 8 operates in a mode in which both smooth and discrete changes in the angle of conduction of the thyristors of the controlled rectifier 2 are performed simultaneously. FIG. 6 shows voltage diagrams for the operation of a low-frequency generator at a frequency of 30 Hz. At frequencies of 100 Hz and below, the address pulses have a sequence, which is shown in FIG. 6a. The pulses (Fig. 66) from the output of the phase-shifting device 8 of a given duration through the control unit 10 are fed to the control input of the switch 6. At the output of the switch 6, address pulses are formed (Fig. Ie), which are amplified by the output devices of the thyristors controlled rectifier. The initiation angle of the thyristors is measured with respect to the natural moment of switching the diodes of the uncontrolled rectifier, which corresponds to the intersection points of the phase voltage curves (Fig. 2a), with the exception of the first two address pulses, in conjunction with the start regulation time interval of the pulse. The operation of controlled rectifier 2 is illustrated by diagrams of instantaneous values of phase voltages (Fig. 6d) on thyristors. The voltage curves on the EDM gap when the low-frequency generator is running are shown in FIG. 6e. The proposed low-frequency generator makes it possible to create a source for EDM machines, which makes it possible to select the optimum mode of operation in each specific case depending on the object of regulation, which is characterized by many factors. The choice of the optimal EDM mode is achieved by synchronizing the operation of the low-frequency generator with the supply voltage network, which allows to obtain the desired duration and duty cycle of the output pulses in the entire frequency range and the accuracy of the pulse energy at a given frequency. Claims of the Invention A low-frequency generator for powering EDM machines, comprising a three-phase power transformer, the inputs of which are connected to a three-phase voltage network, and the outputs are connected to the inputs of a controlled rectifier made on thyristors, the control inputs of which are connected to the outputs of the output device, and the outputs are connected with the tires of the electrical gap and the inputs of the short-circuit protection device, the output of which is connected to the first input of the control unit, synchronizer, inputs The three-phase voltage network is expensively connected, and the output is connected to the second input of the control unit, a phase shifter whose inputs are connected to the first outputs of the control unit, and a module that has an output connected to the third input of the control unit, in order to increase synchronization accuracy; a time interval former is entered into it; its outputs are connected to the fourth inputs of the control unit, one input is connected to the output of the phase shifting device, and the second inputs are connected to the additional synchronizer outputs, an address pulses switch, the outputs of which are connected to the inputs of the output device, and control inputs are connected to the second outputs of the control unit, an address pulse pulses, the outputs of which are connected to the signal inputs of the switch of address pulses, and inputs are connected to the signal outputs of the synchronizer. Sources of information taken into account in the examination 1.Livshchits A.P. and others. Pulse generators. M., “Energie, 1970, p. 158, fig. 8-1. 2. USSR author's certificate number 301247, cl. B 23 P 1/02, 1970. but g I ptp pgppppppppppg gtgp one b Software Uo5 U6c Uca / -v- p / -r rv I PGP pg g teJ y11 iii five 6 UQ Ud Uc to m V a i / 0 uca Ll II J i R Uh FIG. x1 / /. nn Q GT five ri ri Uq UQ6 Udc UcQ // X  / / / / / l v v ri n n GT n GT X / / Have V / / / , 5 Ud but