RU1810969C - Device for controlling power - Google Patents

Abstract

Usage: the invention relates to electrical engineering and can be used in three-phase voltage electric heating furnaces under active load. SUMMARY OF THE INVENTION: a power control device comprises three bi-directional keys 8 connected between a terminal for connecting a corresponding phase of the network and a terminal for connecting a corresponding phase of a load 7. A control terminal of a bi-directional key of the first phase is connected through an amplifier 6 and a one-shot 5 to the output of the switching signal generator . The synchronizing pulse generator 9 is connected to the output by an input for connecting the first phase of the network. Bidirectional keys 8 are made in the form of counter-parallel connected diode and thyristor. The switching signal generator comprises a control signal sensor 1, the output connected to the input of the comparison circuit 2, the first output of which is connected to the input of the phase-shifting unit, the synchronization input of which is connected to the output of the synchronizing pulse shaper 9, and its output is the output of the switching signal shaper, Scheme the comparison contains two threshold elements, two diodes and a subtracting element, the output of which is the output of the comparison circuit 2, and its positive input is the input of the comparison circuit 2 and soy Inonii to the inputs of the threshold elements, the outputs of which are connected through respective diodes to the negative input of the subtractor element. The phase-shifting unit contains a controlled frequency generator 3 and a frequency divider 4-5 or i x XL-L Г 7 1 С /) С 00 о о о ю

Description

The invention relates to electrical engineering and can be used in three-phase voltage electric heating furnaces under active load.

The purpose of the invention is to ensure strict symmetry of the control pulses to maintain smooth and precise control, reliability at low cost of the control and power parts, small size and weight of the entire device.

In FIG. 1 shows a block diagram of an inventive device; in FIG. 2 - graphs of the output voltages of the blocks included in the device; in FIG. 3 - options for connecting the load to the network if the transition from one interval to another occurs in manual mode; in FIG. 4 is a graph of voltages at the load of each phase; in FIG. 5 is a block diagram of a comparison scheme.

The proposed device consists of a driver of switching signals, including / a sensor 1 of a control signal; comparison circuit 2; controlled frequency generator 3; frequency divider 4; single vibrator 5; amplifier 6; shaper 9 synchronizing signals.

A controlled frequency generator and a frequency divider together create a phase-shifting device.

Three outputs of the driver of the switching signals are connected to three, respectively, of the control inputs of block 8 of three bi-directional switches, switching three-phase. Load 7.

In this case, the output of the control signal sensor 1 is connected to the input of the comparison circuit 2. The first output of the comparison circuit 2 is connected to the input of the controlled frequency generator 3, the output of which is connected to the counting input of the frequency divider 4. The network voltage is supplied to the input of the synchronization signal generation circuit 9 . The output of the sync signal generator 9 is connected to the reset input of the frequency divider 4, The output of the frequency divider is connected to the input of the one-shot 5. The output of the single-vibrator 5 is connected to the input of the amplifier 6. The output of the amplifier 6 is connected to the control input of the valve key 8 of the first phase.

The control signal sensor provides a signal whose magnitude corresponds to the power that the network load should consume. In automatic mode, this can be the output of the automatic control system. In manual mode, it can be a variable resistor, the input of which is supplied with a constant voltage.

The comparison circuit includes two threshold elements 10 and 11; two diodes 12; subtracting element 13.

Signal from control signal sensor

arrives at the input of the comparison circuit, to which the first inputs of two threshold elements and the positive input of the subtraction element are connected. The second inputs of the support elements are supplied with reference signals,

equal 1/3 and 2/3 of the input maximum. The output of the threshold element with the input Uon 1/3 Umax is connected to the input of the diode and to the control input of the thyristor of the second phase. Threshold element output with input

Uon 2/3 Umax is connected to the input of the second diode and the control input of the thyristor of the third phase. The outputs of two diodes 12 are connected to the negative input of the subtracting element 13. The output of the subtracting

element arrives at the input of the phase-shifting device. The threshold elements 12 are controllable keys in which the first input is control. If the signal arriving at first

input, more than the reference signal, then the reference signal is supplied to the output. Otherwise, the key is open and there is no signal output. From the output of the threshold elements, the signals pass through the diodes to the negative input of the subtracting element. The output of the subtractor receives the difference between a positive input signal and a negative one.

The entire control range is divided

into three intervals. At each interval, the power is regulated within 1/3 of the maximum value.

The phase shifting device, having received an input signal, transmits it to its output

after a controlled period of time equal to the thyristor opening angle.

A single-vibrator generates at its output the required signal duration necessary to turn on the thyristors. The amplifier amplifies the current and voltage signal. When the voltage of the mains voltage passes through zero, the clock driver generates a signal at its output. In the first interval, only the first phase thyristor opens.

The opening angle of the thyristor is generated by a comparison circuit, a source of a control signal, a generator and a frequency divider. Load power

varies from zero to 1/3 of the maximum,

The second interval requires, in addition to the thyristor of the first phase, the opening of the thyristor of the second phase by the control signal generated by the comparison circuit. Power is adjustable from 1/3 to 2/3 of the maximum.

At the third control interval, the thyristor of the third phase from the third output of the comparison circuit is additionally opened. Power is adjustable from 2/3 to maximum. The turn-on angle of the thyristor changes only in the first phase. As the control signal from the sensor 1 increases from zero to 1/3 of the maximum turn-on angle of the thyristor of the first phase, it changes from zero to one hundred and eighty degrees. At the beginning of the second interval, the turn-on angle of the thyristors of the first phase will be equal to zero, similarly to & The clock from block 9 resets the counter value of the frequency divider.

The economic effect is achieved by increasing the accuracy of power control, improving the quality of the process, reducing the harmful effects of voltage and current surges on the load. The service life of the load and the device itself increases. The device itself is simplified and its cost is reduced.

SUMMARY OF THE INVENTION A power control device comprising three bi-directional switches connected between a terminal for connecting an appropriate phase of a network and an terminal for connecting an appropriate terminal |

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phase of the load, while the control terminal of the bi-directional key of the first phase through the amplifier and the one-shot is connected to the output of the driver of the switching signals, in addition, the driver of the synchronizing pulses, the input connected to the output to connect the first phase of the network, characterized in that, in order to improve the quality of the output power by reducing inrush currents and voltages, increasing accuracy and simplification, bidirectional switches are made in the form of counter-parallel connected diodes and thyristors, and the driver includes of the input signal contains a control signal sensor connected to the input of the comparison circuit, the first output of which is connected to the input of the phase-shifting unit, the synchronization input of which is connected to the output of the driver of synchronizing pulses, and its output is the output of the driver of switching signals, while the comparison circuit contains two threshold element, two diodes and a subtracting element, the output of which is the output of the comparison circuit, and its positive input is the input of the comparison circuit and is connected to the threshold inputs elements whose outputs through respective diodes connected to the negative input of the subtractor element.

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