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THE SCHEME OF THE STABILIZER OF THE NETWORK VOLTAGE ON 4,5кВт

To stabilize the mains supply voltage in domestic conditions, mainly use ferro-resonance stabilizers. Among their shortcomings include the distortion of the shape of the output voltage curve, the inability to work without load. In addition, industrial-produced ferro-resonance stabilizers for domestic use have a low power ( 300 ... 400 W ), which is often not enough, for example, in the garden.

From these shortcomings, a voltage stabilizer, made on the basis of a regulated (laboratory) autotransformer, is free. Such a stabilizer is an automatic control system in which a part of the output voltage is compared with the established reference voltage. Depending on the sign of the difference of these voltages, the movable contact of the autotransformer with the help of an electric motor moves so that the output voltage approaches the model voltage.

A schematic diagram of the voltage regulator is shown in Fig. 96 . As an autotransformer T1 used autotransformer type AOSN-20-220-75U4, manufactured by the industry . Its windings are rated for current up to 20 A , and the maximum voltage taken from movable contacts is 240 V.

The transformer is made on a rod ( U-shaped ) magnetic circuit. The winding consists of two parts, each of which slides the graphite slider ( B2 and B3 ). The input voltage of 220 V is applied to the contact-outlets A2 and A3 .

While the contacts of the switch SA1 are closed, the output voltage from contacts B2 and VZ through the resistor R1 is applied to the diode bridge VD1 . The ripple of the rectified voltage is smoothed by the capacitor C1 and from the slider of the trimmer R2 are applied to the inputs of the comparator chips DA1, DA2 . The second inputs of the comparators are supplied with an exemplary voltage taken from the parametric voltage regulator VD2R3 and from the adjustable voltage divider R4R5 . The output voltages of the comparators via the switch SA2 and the LEDs HL1, HL2 are applied to the LEDs of the optocouplers Ul, U2 . Dinistors of optocouplers are included in the diagonal of diode bridges VD4. VD5 , which control the supply of voltage to the windings of the motor Ml - asynchronous reversible motor with gearbox type RD-09 . If the isolator of the optocoupler Ul is open, the motor shaft rotates in one direction; If the transistor of the optocoupler U2 is open, the motor shaft rotates in the other direction.

The motor windings are powered by a voltage of 127 V , which is removed from the terminals 4 and 10 of the primary winding of the transformer T2 . Condenser C4 provides the necessary phase shift between voltages on the windings of the motor.

The power source of comparators DA1, DA2 , parametric

The circuit of the mains voltage stabilizer is 4.5kW.

Stabilizer VD2R3 and voltage divider R4R5 is an integral stabilizer, implemented on the chip DA3 .

The device works as follows. If the output voltage of the transformer T1 corresponds to the norm, the voltage on the engine of the adjusted resistor R2 will be less than the voltage at terminal 3 of the comparator DA1 , but greater than the voltage at terminal 4 of comparator DA2 , and the output current of both comparators is zero. In this case, the diodistors of both optocouplers are closed, no current flows through the windings of the electric motor, and the sliders of the autotransformer T1 are fixed.

In case of increasing the mains voltage, the voltage values ​​at contacts B2 and V3 of the transformer and on the resistor R2 will increase. As a result, the voltage at pin 4 of comparator DA1 will exceed the voltage at pin 3 , and current will flow through pin 9 of the comparator. The transistor of the optocoupler U2 opens. The state of the comparator DA2 does not change. Via the diode bridge VD5 and the windings of the Ml motor, a current will flow, causing the shaft to rotate. The sliders will move along the windings of the T1 windings in the direction of reducing the output voltage. After a while, the voltage will reach normal, the comparator DA1 will switch to the initial state and the motor will stop.

When the mains voltage drops in the active state, the comparator DA2 and the optocoupler U1 will appear, and the motor shaft will move the B2 and BZ sliders in the direction of increasing the output voltage. Thus, it will be maintained at a given level.

The range of possible output voltage values ​​(i.e., the accuracy of stabilization) is determined by the difference in voltage levels at pin 3 of the DA1 chip and pin 4 of the DA2 chip and is set by a trimmer resistor R4 .

The capacitor C 1 not only smoothes the ripple of the rectified voltage, but also filters the noise that occurs during short-term changes in the mains voltage. If the duration of the interference does not exceed 1.5 ... 2 s, the device does not respond to it. Resistor R6 limits the current through the diodes of the optocouplers.

The switch SA1 , the buttons SB1 and SB2 are designed to control the motor in manual mode, when the electronic unit of the device is switched off. SF1 and SF2 are the contacts of the limit switches. When the sliders B2 and V3 of the transformer T1 are in the extreme positions (upper or lower), the contacts of the limit switches open and shut off the motor, excluding the damage to the mechanical parts of the stabilizer. This can happen, for example, with a significant decrease in the mains voltage, if the movement of the sliders does not lead to the establishment of a nominal voltage at the output. Switch SA2 allows you to change the direction of rotation of the motor shaft. Such a need may arise in the case of the connection of the terminals of the transformer T1 windings other than in the diagram, or in the case of using a transformer T1 of a different type (this will be discussed below).

LEDs HL1, HL2 allow you to visually monitor the direction of rotation of the motor shaft.

In the voltage regulator, the following types of parts can be used. As the comparators can work and chips of types K521SAZ, K521CA5, K521CA6 . The latter type of microcircuit contains two comparators in one housing. Optocouplers U1 and U2 can be any of the AOU103 series, except for AOU103A , a and AOU115B (B) . Diode bridges can be, in addition to the types of KC402, KC405 with letters AB, G, I , indicated on the diagram. Zener diode VD2 it is desirable to use with a low value of the temperature coefficient of voltage, for example, D818 with any letters. But if high requirements are not imposed on the temperature stability of the regulated voltage, it is possible to use other types of stabilitrons with a stabilization voltage of ... 10 V , for example, KS168A, KS175A, KS191A, D814A (B, V) .

Capacitors C1,. C2 - oxide K50-16, K50-6 or K50-29: SZ-KM-6, K 10-17; C4-K73-17 . All the permanent resistors - types MLT, C2-23, C1-12 ; Adjusted R2 and R4 - SP5-2, SPZ-19, SDP-38 . Limit switches SF1, SF2 and buttons SB1, SB2 - KM 1-1, KM2-1 ; Switches SA1, SA2 - toggle switches TZ, P2T-1-1, MTZ .

The electric motor M 1 is of the RD-09 type with a reducer, the speed of the output shaft is 5 ... 20 rpm (reduction ratio is 60 ... 240 ). Such motors are used in self-recording potentiometers. As a transformer T2 can be used TPP238-127 / 220-50 or any other power not less than 10 W , having a tap in the primary winding of 127 V , a secondary winding for a voltage of 18 ... 22 V and a current of not less than 100 mA .

To convert the rotational motion of the motor shaft to the translational motion of the sliders of the transformer T1, a helical pair with a thread M12x 1.7 is used . With its screw, the motor shaft is connected through a transition sleeve. At a shaft speed of 15 rpm, the output voltage changes at a rate of about 0.5 V / s .

The device setup consists of setting the value of the rated output voltage by resistor R2 and in setting the accuracy of voltage regulation by resistor R4 . In the author's copy of the stabilizer at a nominal voltage of 220 V, the control accuracy was ± 3% . Theoretically, the stabilizer is able to ensure the accuracy of the control within a tenth of a percent - for this we need only increase the capacity of the capacitor C1 . But then it will react and to minor fluctuations in the mains voltage caused by random causes (for example, connecting and disconnecting electrical appliances); This can lead to premature wear of the mechanical moving parts of the device.

During the adjustment, select the position of the switches of the SA2 switch, so that when the voltage deviates from the normal load, the motor shaft rotates in the direction that stabilizes this voltage.

This stabilizer was made to maintain a nominal voltage of 220 V in the cottage under the conditions of a significant reduction in the supply network voltage. At the maximum load ( 4.4 kW ), the minimum input voltage at which the stabilizer performed its function was about 180 V. With further lowering of the mains voltage, the limit switch was triggered, and the stabilization mode stopped, since the sliders were in the lowest (according to the scheme) position. In order to avoid such a situation, it may be recommended to interchange the terminals of the transformer windings A2AZ and B2B3 and simultaneously change the position of the contacts of the SA2 switch. In this case, the mains voltage will be applied to the B2V3 sliding contacts, and the load will be connected to the terminals of the A2AZ windings. Now stabilization will be ensured at an arbitrarily deep drop in the mains voltage (even up to 50 ... 60 V ), but it should be remembered that since in any case the current through the В2ВЗ outlets can not exceed 20 A , the maximum output current should be so much less This value, how many times the output voltage is greater than the input voltage. This follows from the condition that the powers of the input and output circuits are equal.

But this way of including winding parts has a disadvantage:

With a sharp increase in the input voltage to the mains through the B2ZZ sliders, a disproportionately small number of windings of the transformer winding will be connected, and while the automatic control system will work through the input, an excessively high current will flow through the contacts of the В2ВЗ , and an unacceptably high voltage will act on the load. In order to partially prevent this drawback, it is possible to limit the movement of the autotransformer sliders by the appropriate setting of a limit switch that would work when the input voltage is reduced to 150 ... 160 V , and further movement of the sliders towards the reduction in the number of turns of the windings connected to the network is stopped.

The device is suitable for stabilizing the output voltage in the range from units of volts to 220 V. To ensure an output voltage of less than 70 ... 80 V, the primary winding of the transformer T2 should be directly connected to the 220 V network and, in addition, to reduce the value of the resistor R1 to 47 ... 56 kΩ. For an output voltage of less than 10 V, the Zener diode VD2 will have to be replaced by another, whose stabilization voltage should be 1 ... 2 V less. Than stabilized. As a transformer T1 , toroidal autotransformers of the LATR -2 and LATR-9 types can also be used, but in this case the permissible load power will decrease; It is necessary to apply the RD-09 engine with a lower speed ( 1 ... 2 rpm ) and select the corresponding position of the contacts of the switch SA2 .

This device is convenient to use in school in physics lessons, and in the radio circle when setting up devices.

To ensure reliable soundproofing, the autotransformer should be installed on a rigid base through felt or rubber pads that have good sound-absorbing properties.

print version
Date of publication 25.12.2003gg