Electronic relay voltage stabilizer, 145-275 / 187-242 volts. Scheme, description

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Electronic relay voltage stabilizer, 145-275 / 187-242 volts. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Surge Protectors

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When the mains voltage changes from 145 to 275 V, the voltage at the output of the stabilizer changes in the range of 187 ... 242 V (220 V ± 10 ... 15%), which is acceptable for powering most household electrical appliances. The scheme of the device is shown in fig. 1.

(click to enlarge)

Transformer T1 is included as an autotransformer. Depending on the position of the moving contacts of the relays K1.1 and K2.1, the secondary windings II (35 V), III (10 V) and IV (15 V) will be connected to the load in-phase or out of phase with the mains voltage. The electronic part is powered by the IV winding. Its voltage rectifies the diode bridge VD1 and then smoothes the capacitor C2.

The supply voltage of the electronic part is stabilized by an integral stabilizer DA1 with an output voltage of 12 V. The voltage of the IV winding is used to control the mains voltage. To do this, it is rectified by the diode bridge VD2 (the output voltage of which is smoothed by the capacitor C1) and from the resistive divider R2 R3 R4 is supplied to the non-inverting inputs of the comparators assembled on the op-amp DA2.1 - DA2.3. The inverting input of the op-amp DA2.1 receives voltage from a parametric stabilizer assembled on a resistor R9 and a zener diode VD3. The inverting input of the op amp DA2.2 is supplied with voltage from the voltage divider R5R6, and the inverting input of the op amp DA2.3 is supplied from the divider R7R8. Resistors (R10-R12) are included in the positive feedback circuit of each op-amp, which provide hysteresis when switching comparators and thereby increase the noise immunity of the device.

LEDs HL1-HL3 indicate the state of the comparators, at a low voltage level at their outputs they shine. LEDs are necessary in the process of establishing, after its completion they can be dismantled. To the outputs of the op-amp DA2.1 and DA2.2 connected logical elements "exclusive OR" DD1.1 and DD1.2, which together with the element DD1.3 and comparators set the algorithm of the device. On transistors VT1, VT2, electronic keys are assembled that supply voltage to the relays K1 and K2. The R1C3 circuit is "spark arresting", the diodes VD4 and VD5 protect the transistors from the self-induction voltage of the relay windings, which occurs when the transistors are closed, and the capacitors C7, C8 increase the stability of the relay switching (eliminate contact bounce).

The operation algorithm of the device and the voltage values at the inputs and outputs of the comparators are given in Table. 1.

Table 1, device operation algorithm and voltage values at the inputs and outputs of the comparators

(click to enlarge)

At a low level (log. 0) at the outputs of the comparators, the corresponding LED will be turned on. The position of the relay contacts in the diagram is shown in the de-energized state. The device has four levels of regulation. With a mains voltage of 145 to 180. V, the voltage at the engine of the resistor R4, and hence at the non-inverting input of each op-amp, is less than at their inverting input. Therefore, the outputs of all comparators are low (all LEDs are on). The output of element DD1.3 is also low and transistors VT1 and VT2 are open. The supply voltage is supplied to the relay, the moving contacts of groups K1.1 and K2.1 are in the lower position according to the diagram. The voltage at the load is equal to the mains voltage plus the "voltage boost" voltage taken from the secondary windings II, III and IV of the T1 transformer. In the above range of changes in the mains voltage at the load, it will vary from about 187 to 239 V.

With a mains voltage of 180 ... 197 V on the engine of the resistor R4, the voltage changes in the range from 4,85 to 5,3 V, therefore, at the non-inverting input of the op-amp DA2.2, it will become greater than at the inverting one and it will switch (the HL3 LED will go out) . A high level will be set at the output of elements DD1.2 and DD1.3, transistor VT2 will close, relay K2 will de-energize, and its contacts K2.1 will switch. 8 In this case, the voltage at the load will be equal to the mains voltage plus the "voltage boost" voltage taken from the winding II of the transformer T1, i.e. 205...224 V.

When the mains voltage is in the range of 198 ... 230 V, the voltage on the engine of the resistor R4 can vary from 5,31 to 6,2 V, which is more than at the inverting input of the op-amp DA2.3. The comparator on this op-amp will switch (the HL1 LED will go out), and a high level will be set at the output of the DD1.3 element.

Therefore, the transistor VT1 will close, VT2 will open. Relay K2 is on, and K1 is off. In this case, the mains voltage is supplied, bypassing the secondary windings of the transformer T1 directly to the load.

When the mains voltage rises to 231 ... 275 V on the engine of the resistor R4, it will exceed 6,2 V, the comparator on the op-amp DA2.1 will switch (the HL2 LED will turn off), which will lead to a high level at the output of the element DD1.3. Both transistors are closed and the relays are de-energized. Therefore, the voltage at the load will be equal to the mains voltage minus the voltage of the windings III and IV of the transformer T1, i.e. 198 ... 224 V.

Most parts of the stabilizer are mounted on a breadboard PCB using wired wiring. Resistors MLT, S2-23, oxide capacitors - K50-35 or imported, capacitor C3 - K73-17 are used. diode bridges. KTS407A can be replaced by any of the series. KTs410, KTs412 or DB107. LEDs - any color of glow, which provide the required brightness of the glow at a current of 10 mA. The power switch must be designed for switching mains voltage and current of at least 5 6, and switches B1201, 31202 are suitable. The relay should be selected from the TR90 series (for example, TR90-12VDC-FB-C), TR91 (for example, TR91 (F) -12VDC-FB-C), others with a switching voltage of 12 V and changeover contacts designed for switching an alternating voltage of at least 250 V and a load current of at least 5 A are also suitable.

In the author's version, the transformer is wound on a ring magnetic circuit with an outer diameter of 176 mm, an inner diameter of 120 mm. height - 90 mm from electrical steel. All windings are wound with wire. PETV-2 or PEV-2, primary - with a wire with a diameter of 0,7 mm, secondary - 1,2 ... 1,5 mm. Winding I contains 370 turns, and windings II, III and IV - 60, 18 and 26 turns, respectively. It is possible to use a unified transformer TPP-322, its connection diagram is shown in fig. 2.

Electronic relay voltage stabilizer, 145-275 / 187-242 volts

To establish a stabilizer, you will need a LATR and a multimeter.

Adjustment is carried out in the following sequence. Connect the device to the network without load and check the performance of the integral and parametric voltage stabilizers. The voltage is pre-set at the inputs of the comparators. Trimmer resistors R5, R7 are set at the inverting inputs of the op-amp DA2.1 and DA2.3 voltage in accordance with the table. If the mains voltage is within normal limits, the resistor R4 sets a voltage of about 4 V on the capacitor C6.

Then, a real load is connected to the output of the device so that the reaction of the transformer T1 to it is taken into account, and the input of the device is connected to the output of the LATRA. A voltage of 230 V is set at its output.

By smooth rotation of the engine of the resistor R4, the moment of operation of the comparator on the op-amp DA2.1 is achieved - all LEDs should go out. Next on the way out. LATRA set the voltage to 180 ... 181 V, and all LEDs should turn on. The trimmer resistor R5 is used to achieve switching of the comparator DA2.2 (extinguishing of the HL3 LED). By setting a voltage of 197 ... 198 V at the LATRA output, the trimming resistor R7 achieves the switching of the DA2.3 comparator (the HL1 LED goes out). The switching thresholds should be checked again, and if necessary, the adjustment should be repeated.

The board and transformer are installed in a case of suitable dimensions.

A fuse holder and a socket for connecting the load are mounted on the rear panel, and a power switch is mounted on the front panel. If it is necessary to indicate the operation of the stabilizer, LEDs can also be placed on the front panel; in this case, they can be of a different glow color.

Author: Gadzhiev G.

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