Universal power supply, 2-300 volts 0,9 amps (2-22 volts 6 amps). Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Power Supplies

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Every radio amateur knows: one cannot do without a source of constant and alternating voltages of various values ​​in practical work. It is needed to set up radio structures, repair equipment, charge batteries, test electric motors and relays, and conduct physical experiments. All this can be done using a universal power supply, the description of which we bring to the attention of readers.

The device allows you to receive smoothly varying voltages in the range of 2-300 V up to 900 mA AC and 600 mA DC or 2-22 V at a current of up to 6 A.

Rice. 1. Schematic diagram of the power supply (click to enlarge)

Using switch S6 (Fig. 1), the power supply mode is set to five positions, as indicated by the corresponding lamps H1-H5.

The voltage in the range of 2-22 V is selected in steps of 2 V by switching S4, and in the range of 2-300 V - S3 through 26 V.

Toggle switch S2 transformer T1 is transferred to autotransformer mode to power more powerful current consumers.

Alternating current is converted to direct bridge rectifiers on diodes V1-V4 and V5-V8. To exclude the possibility of failure of the filter C1, V9, C2, a toggle switch S5 is installed, which must be in the "off" position when the high-voltage load is disconnected.

Rectifier V1-V4 operates in universal mode. In the fourth position of switch S6.1, a voltage of 2-22 V is supplied. In the third position of S6.1, with the toggle switch S5 closed, the high-voltage winding of the transformer is connected to the bridge.

The rectified voltage in the 2-300 V mode from the filter C1, V9, C2 is supplied to the output terminals of the power supply. In the 2-22 V mode, a constant voltage is supplied to the second filter, made on transistors V12, V13.

The rectifier on diodes V5-V8 is connected to T1 permanently.

The values ​​of voltages and currents are controlled by two pointer indicators PV1 and PA1. The ammeter scale has two measurement limits: 0-900 mA and 0-6 A. To measure currents up to 90 mA, the S7 toggle switch includes an additional shunt that divides the instrument readings by 10.

Construction and details. Perhaps the most time-consuming process is the manufacture of a transformer. TS-180-2 is taken as a basis - a power transformer from black-and-white TVs. It has a tape magnetic circuit SL21X45 made of steel E-310-0,35.

The transformer is disassembled, secondary and additional network windings of 58 turns are wound from its frames (pins 2-3). And the network windings of 375 turns of wire PEV-1 0,69 (pins 1-2) are left unchanged. Then, on one of the frames, sections XXII-XVII, XII, XI, X, IV, III, II (563 turns) are placed in the indicated sequence, on the second - XVI-XIII, IX-V (508 turns).

Sections II to XI contain 96 turns each, and XII has 34 turns of PEV-1 0,69 wire. The winding of ХХШ-XIII is wound with PEV-1 wire 1,5, 7 turns in each section. It can be wound with two wires of a smaller cross section, for example, PEV-1 0,74.

Each winding row is insulated with 2-3 layers of oiled transformer paper. The conclusions are soldered to the petals located on the frames and marked.

Between the joints of the U-shaped halves of the tape magnetic core, if necessary, lay 2-3 layers of capacitor paper so that the gap is 15-30 microns. Then the "buzz" of the transformer will become much weaker. After completing the assembly, connect the network windings together as shown in the diagram.

Transistors and diodes D242 are mounted on heat sinks (see Fig. 2) - an aluminum plate 90X50X1 mm in size for the first and two aluminum plates 2 mm thick stacked together for the second.

Rice. 2. Power transformer with installed elements: 1 - heat sink for D242 diodes, 2 - heat sink for transistors, 3 - panel with KD202M diodes, 4 - panel with resistors R3-R6, 5 - getinax board.

Instead of the P4BE transistor, it is permissible to use GT701A, P209, P210, and instead of P201, P213, P214, P216, P217 with any letter index are suitable. Diodes KD202M can be replaced with KD202K, KD202L or D226B, KD105, connected two in parallel; D242 - on KD206 with any letter index or D243, D244, D245; D9E - any series D2 or D9.

Capacitors C1, C2 K50-12 have a common housing. They can be replaced with any others with an operating voltage of at least 350 V. Instead of capacitors K50-6 (C3, C4), K50-3 can be used. Fixed resistors MLT-1 or VS-1.

S1 - push-button switch from household electrical appliances, S2 - toggle switch TP-1-2, S3, S4, S6 - toggle switches, S5, S7 - toggle switches TV2-1.

PV1 - voltmeter Ts4200 with a full deflection current of the arrow 250 μA, RA1 - M4207 microammeter with a full deflection current of 50 μA. These measuring devices can be replaced by any other within the specified sensitivity. Indicator scales are made independently in accordance with the general drawing.

Shunts R7, R9, R10 are wound with nichrome wire Ø 0,3 mm on the cases of resistors BC-0,5 with a conductive layer previously removed. The shunt resistor R0,15 is also wound with the same wire, but Ø 11 mm. Shunts R8 and R12 are pieces of nichrome wire Ø 0,7 mm and 2-3 cm long. Nichrome wire can be replaced with manganin or constantan, but then the winding length will need to be doubled, since the resistivity of these materials is less. Shunts are installed on switch S6.

H1-H5 - KM 2 switching lamps are designed for a voltage of 24 V. They can be replaced with any others by removing the appropriate voltage from the transformer.

The power supply unit is housed in a duralumin case measuring 190X180X125 mm. In its side walls, 7-8 longitudinal ventilation slots 80x2 mm in size are made, and in the base - 2-3 holes Ø 20 mm.

The unit does not have a special chassis. The supporting elements are the front panel and the power transformer. Installation is made with stranded wires assembled in bundles.

The front panel measuring 180x170 mm is made of sheet duralumin 2 mm thick. A sheet of whatman paper with inscriptions made in black ink is superimposed on it, and covered from above with plexiglass 2 mm thick.

Pushbutton switch S1 is mounted on top of the housing.

If the installation is done correctly and all parts are in order, the power supply starts working immediately after it is connected to the network. It will be necessary to adjust only the values ​​​​of additional resistors and shunts for dial indicators.

Author: A.Medvedev

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