SU381186A1 - PORTABLE RENTGENOVSKY ANPARAT - Google Patents

Description

one

The invention relates to X-ray technology and can be applied in medicine for diagnosis, 11 studies by X-ray and fluoroscopy.

One of the most common diagnostic x-ray machine circuits designed to operate on a 50 Hz line voltage is a transformer circuit.

In this circuit, there is no rectifier, and a high alternating voltage of about 100 kV from the secondary winding of the transformer is directly applied to the anode of the x-ray tube. Transformers have large dimensions and weight.

An x-ray apparatus is also known, in which the pa-anode of the x-ray tube is supplied with a miaber formed using a thyristor converter. Due to this, the efficiency of radiation of the apparatus is increased in comparison with the efficiency of radiation of apparatus without a rectifier.

However, for direct connection of the x-ray tube to the high-voltage winding of the transformer, it is required to provide a high-voltage isolation of the transformer corresponding to the anode voltage of the x-ray tube. As a result, it is impossible to significantly reduce the weight and size of the transformer.

In order to reduce the size and weight of the device, reduce the patient's radiation dose and increase the maximum permissible thermal power dissipated by the anode of the x-ray tube, the power supply unit is equipped with a static frequency converter of the supply voltage with a transformer having an additional winding, as well as a cascade rectifier-multiplier connected to the boost winding of the frequency converter transformer. The x-ray tube is controlled at a constant anode voltage by a grid of pulses produced by a magnetic modulator.

FIG. 1 shows the block diagram of the proposed X-ray unit: 1 — a frequency converter, 2 — a cascade rectifier — voltage multiplier, 3 — a master oscillator, 4 — a modulator, 5 — a three-electrode X-ray tube.

FIG. 2 depicted a schematic diagram of the apparatus. The power to the circuit is single phase.

mains voltage of 220 V, 50 Hz, which is supplied to terminals a and b of the frequency converter. The latter is made on thyristors TI and 79 according to a series inverter circuit with an intermediate DC link at

diodes Dx-D4 n capacity Sf. The load of the frequency converter is a step-up transformer Tpi, and the excitation is carried out using a master oscillator 3, assembled according to the circuit of a push-pull voltage converter on the niJi and SAN triodes. Dz and De diodes are used in the secondary windings of the transformer of the master oscillator to cut off the negative impulse.

To power the cathode filament of an x-ray tube, a transformer Gr2 is used, having two additional secondary windings, one of which serves to power the master oscillator circuit 3, and the other to power the time relay 6, which allows setting the exposure time.

When the frequency converter 1 is energized on the secondary winding of the transformer Tp, having four taps in relation to the output, a voltage of 7.5 is induced; ten; 12.5. And 15 kV, respectively, with a frequency of 5 kHz, which with the aid of switch / 7 leads to a cascade multiplier of voltage 2.

The latter contains four stages of multiplication and, depending on the position of the switch Pn, at the output, a voltage of 40, 60.80 or 100 kV can be obtained.

X-ray 5 is switched on with a grounded cathode and operates in a pulsed mode with grid control at a constant anode voltage. The control voltage is formed by a magnetic modulator 4, powered by the auxiliary winding of the transformer Tr. The control pulse is removed from the secondary winding of the output transformer W and is fed to the x-ray tube grid. The amplitude of the control pulse is determined by selecting the magnetisation current of throttles L by means of resistance R. A constant negative voltage of the intermediate link of the frequency converter is used to lock the tube during the absence of the control pulse.

Thus, the introduction of a frequency converter and a cascade voltage multiplier rectifier significantly reduces the weight of the device, since the volume of the transformer magnetic circuit is inversely related to frequency. The presence on the secondary winding of the transformer Tr is only about square, and not 100 / ce,

as in transformer circuits, it can significantly reduce the requirements for their manufacture. In addition, the pulsed mode of operation of the x-ray tube at a constant anode voltage can significantly increase the limiting thermal power dissipated by the anode (it has been established experimentally that when the x-ray tube is operating in a pulsed mode for a maximum of 20 µs sec.

dissipated by the anode can be dramatically increased) and reduce the ineffective dose of radiation.

Subject invention

A portable X-ray machine containing a power supply unit with a cascade voltage multiplier, a control unit, and an X-ray tube with a grid, characterized in

that, in order to reduce the weight and size of the apparatus while simultaneously increasing the radiation power, the power supply unit is equipped with a static frequency converter of the supply voltage with a transformer, equipped with

an additional winding and connected to a cascade voltage-rectifier multiplier, made according to the Cockroft-Walton scheme, and a magnetic modulator was inserted between the X-ray tube grid and the auxiliary winding of the frequency converter transformer.

FIG. ;

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