Voltage stabilizer with double protection

The offered stabilizer has separate protection against an overload on a current and KZ. At KZ on an exit of the stabilizer works protection knot on VT3 (fig. 1). At an overload on a current protection on VS1 and К1 works.

Knot of electronic protection works p, when the current of loading creates on the R6 resistor power failure, sufficient for opening of a tiristor of VS1 i.e. when the difference of tension between an operating electrode and the cathode of a tiristor reaches about 1 Century. The negative impulse of tension arising thus via the VD3 diode arrives on base of the VT3 transistor and practically closes it, and consequently, and the regulating VT1 transistor. At the same time the VD3 diode protects the VT3 transistor from hit on its base of positive tension from an anode chain of a tiristor.

However the electronic system of protection nevertheless does not protect completely the VT1 transistor from thermal breakdown by a residual current, especially if the transistor was already warmed up in the course of work, or long time did not press the SB1 button.

For prevention of thermal breakdown of the VT1 transistor also serves p the electromagnetic system of protection working through some milliseconds (depends on the used K1 relay) after the tiristor of VS1 will open. Then works the K1 relay. Its contacts К1.1 close the VT3 base on the minus conductor of the power supply, and contacts К1.2 include HL2 light-emitting diode — a signaling device of action of protection. After elimination of the reason of an overload rather quickly to press the SB1 button to restore a former operating mode of the power unit, without disconnecting the device from a network.

On an entrance of the stabilizer moves from the rectifier constant tension of 40 Century. The target stabilized tension from 3 In to 30 In is established by the R2 resistor. The maximum current of loading — 2 A.Tok loadings supervise PA1 head, having switched SA1.

of the Detail of the stabilizer are mounted by p on a payment from folgirovanny стеклотекстолита (fig. 2 and 3) and on the obverse panel of the case of the power unit. The regulating VT1 transistor is established on a heat-conducting path. It is possible to replace the KT825A transistor on КТ825Б, G; КТ818В, G, VM, hypermarket; КТ814Г — on КТ814В, B; КТ816Б, In, G; КТ315В — on КТ315Г, Д, Е.

Tiristor КУ202К is replaced with p on КУ201В. . КУ201Л, КУ202В... КУ202Н. Instead of the D220A diode (VD2) will approach Д219, Д220, Д223, КД102, КД103 with any alphabetic indexes, and instead of the KD105B diode (VD3, VD4, VD5) —\ КД106А or any other silicon with a direct current to 300 мА and return tension not less than 50 Century

the Variable R2 resistor — any type with A.Rele K1—s characteristic \ РЭС48А (passport РС4.590.206) or another with two groups of the switching contacts, working at tension no more than 30 Century

the R6 Resistor is executed in the form of several rounds of the konstantanovy, nikhromovy or manganinovy wire which has been reeled up on the case of the MLT-1 resistor. Its resistance is defined by value of a current of operation that, in turn, depends on tension on an operating electrode of a tiristor at which it opens. So, for example, if for the maximum current of operation of protection to take 2 And, and the tiristor opens at tension on an operating electrode about 1 In, resistance of the R6 resistor should be (under the Ohm law) close to 0,5 Ohm. Use of resistors of the C5-16 type of the corresponding capacity is possible.

is More exact resistance of the resistor adjust to the chosen limit of operation of protection in such order. To an exit of the stabilizer connect connected consistently the ampermeter and the wire variable resistor resistance 25... 30 Ohm. On an entrance of the stabilizer submit the corresponding tension from the rectifier, and the R2 resistor establish on an exit tension 10... 15 V.Zatem the variable resistor which is carrying out function of an equivalent of loading, establish a current equal 2 And on the ampermeter, and selection of resistance of the R6 resistor operation of system of protection achieve.

In radio amateur practice are frequent circumstances when from an overload currents of smaller value, for example, 50 or 100 мА, it is necessary to protect not only a voltage stabilizer, but also the device eating from it. Thus it is desirable to have the step system of protection executed, for example, on the circuit, given on fig. 4. Here the R6.1 resistor of the first step calculated on the minimum current of protection 50 мА, is switched on in the stabilizer constantly, and parallel to it the SA2 switch connect R6.2 resistors... R6.5 of four other steps: 100 мА, 500 мА, 1 And and 2 And.

the resistance of resistors Specified on the circuit — rough. More precisely they can be calculated, only knowing tension of opening of the tiristor working in the stabilizer. To measure this tension it is possible so. Cursor of the variable R2 resistor establish in extreme bottom (according to the circuit) situation and connect to it an operating electrode of a tiristor, отпаяв it from right (according to the circuit) a R6.1 resistor conclusion. Then include a food and slowly increase the R2 resistor tension on an operating electrode of a tiristor. At the moment of tiristor opening about what will signal a light-emitting diode, measure by the voltmeter this tension.

R6.2 Resistors... R6.5 are mounted directly on SA2 switch contacts. RS1 resistors and R12 steal up specifically under the available measuring device.

Sources

1. O. Lukyanchikov. A voltage stabilizer with double protection against KZ in loading. — Radio, 1986, N9, Page 56.
2. A.Bizer. Protection devices of power units. — Radio, 1977, N2, Page 47.
Yu.Timlin's
3. . Dual two-polar power unit. — For the aid to the radio fan, вып. 71. — M: DOSAAF, 1980
4. V. Borisov. The stabilized power unit. — Radio, 1979, N6, Page 54.

Author: YU.KURBAKOV, Tula