“SECOND WIND” OF THE REFRIGERATOR

Compression, and adsorption refrigerators often fail due to the fact that they denied Electromechanical relays or breakers on the basis of the bimetallic plates. The first of them is used to trigger synchronous electric motors, serving a compression refrigerator system, and the second are the basis of the tracking systems and maintain at a predetermined temperature level freezer [1]. The reason for failure and the other is a burnout or a mechanical failure of the spring contacts in these devices. Ego especially applies to older models of refrigerators. And often you can see that, because of the insignificant, but hard to handle breakdowns (due to the lack of spare equipment) the throw is still quite usable machines. In the material made the attempt to remove such faults in household appliances.

 

It is known that the old scheme run asynchronous motors with starting relays today it is possible to replace the capacitor circuit. Mechanical contacts are missing completely [2]. On the device is also temperature control in the freezer we can say the following. Because the refrigerator is running in the apartment, where the temperature year-round is supported in a sufficiently stable comfortable range (with air-conditioning, Central heating, etc.), in these conditions, the temperature difference between the environment of the apartment and the freezer (good working refrigerator) remained almost unchanged. System temperature control of the refrigerator only “feeds” the freezer stable portions of cold equal to the outflow into the air of the room. Therefore, to maintain temperature at the desired level does not need to monitor the temperature changes, but rather to determine the amount of servings the cold. This can be done indirectly by calculating the time intervals between the start and stop of the compressor of the refrigerator in which the temperature control system is working properly. Then in the fridge to faulty termoregulirovanija, padav certain and constant intervals of work and downtime of the compressor, get a fairly stable temperature in the freezer and its internal volume. This opens the opportunity to build timesnow chain, forming the intervals of the on and off compressor motor without Electromechanical contacts. On these principles and constructed is presented in figure electric circuit, which was upgraded refrigerator “ZIL Moscow” edition, 1956, and are now fully functioning, although prior to alteration has failed on the above mentioned reasons.

 

The scheme works as follows.

 

Master oscillator on the chip DD2.2, DD2.3 generates clock pulses that are close to the form of “meander” in the two modes of formation (analog MOP key DD3 is used to ensure switching from one mode to another). In the first mode produces pulses with a constant repetition period of about 0.6 s (in the closed state of the MOP key part of the DD3), and the second with tunable repetition interval from 0.6 to 0.8 s (in the open position of the same key). The restructuring is provided by the potentiometer R5. In both cases, pulses are generated at levels close to the supply voltage level (0V to 10V). The level of the log.1 the control input DD3 (vyv. 15) corresponds to the first formation mode, and the log level. 0 — the second. For these two modes will be clear from the further discussion.

 

One of the conclusions of the master oscillator (vyv.2 DD2.2) the generated pulses are input to the binary counter on the chip DD1, and he shall divide these pulses by factors of 2 to 16 384 in the range of 14 bits. Each category has its own individual output (except the 2nd and 3rd), with which you can remove pulses through periods of 1.2 s (at pin 9 Junior level) to 3.6 h (at pin 3 high order). Each successive bits (in ascending order) increases the repetition period of pulses in half. Practical importance to control the period of glamourati, modernized according to the proposed principle, have pulses only from the 11th and 12th digits (vyv.1, 15), the frequency of which is close to the rhythm of the work fridge with healthy termotape in steady mode (20 to 40 minutes). The reason for this choice was the observation of the operation of the refrigerator before it spoiled. Then it was noticed that the thermostat was turned on the compressor for 20 minutes and off about the same time.

With vyv.1 DD1 through a buffer inverter DD2.1 is chosen so the pulses are applied to the electronic switch of induction motor-compressor. This switch consists of a transistor VT1, working in a key mode, and two optotiristors — U1 and U2. When the logic level state on the battery + 1 DD1 (counter) reaches the log. 0, via buffer inverter DD2.1 and limiting resistor R1, it goes to the base of transistor VT1 and opens it. In this state, the transistor has a very small resistance between collector and emitter (less than 1 Ohm) and thus lower the circuit output resistor R2 is connected to the ground potential. Via series-connected LEDs in the composition optotiristors U1 and U2 starts to leak current (about 60 mA) -and they light up, and their light exposure leads to a shift of the p-n-p-n thyristor structures in these devices in the open state. Because the thyristor structure included counter-parallel, as increasing. so the decreasing half-periods of the mains voltage get access to the windings of the motor part of the compressor and it starts to work. Its operating winding directly, and starting — through the capacitor C1 to be connected to 220 V. due to OPTOTRONIC pairs composed of U1 and U2 is achieved by the separation of power circuit and control circuit, which is very favorable for electrical safety and reliability of the refrigerator.

 

Capacitor C1 is used to start asynchronous motor hadagreed in single-phase mode. These motors usually contain two windings is working and starting, shifted relative to each other at an angle.

 

The capacitance of the capacitor required to run can be calculated by the formula given in the book of I. Aliyev to such configuration of the windings[2]:

 

C(UF) =1600 I n/u n where:

 

I n — phase current of the motor, u n is the nominal phase voltage. Before the refrigerator is out of order, managed to measure the phase current (the current consumption of the refrigerator in the mode when the compressor is running). Measurement gave 1.6 A. the Nominal phase voltage is known – 220 V. inserting these values into the formula, we get the value from the capacity of about 12 UF. To ensure the reliability and safety of operation requires that the capacitor of such capacity was the margin of operating voltage. Stop the choice on the capacitor K42-19-12 µf±10% 500, which provides shift current in the starting winding relative to the working angle of about 90°. The shift winding leads to the appearance in a magnetic field of the stator power so that contains torque. When exposed to them on the rotor is running the motor. However, the presence of these lines of force creates a barrier to the working coil to perform its function pulsating shocks to influence PA the rotor, maintaining the stability of its momentum. As a result, the magnetic field acting on the rotor, if such inclusion is starting to contain a reactive component, resulting in the return of some part of power consumed by the motor, in the supply network [2]. However, in view of moderation and constant load PA shaft, these losses are insignificant and the remaining part of the motor power is sufficient to ensure operation of the compressor. It is, moreover, saves electricity a refrigerator consumes less network capacity. Phase current, which was measured after upgrading the fridge will be 1.1 A. Thus, the need to use the launcher disappears turnips.

 

 

Schematic diagram of the timer, providing the work of the home refrigerator in case of failure of the system temperature control

 

Oversee the work of the unit before it breaks, as already noted, indicate that the steady-state mode kholodoobespecheniya it occurs when the approximate equality of the 20-mi-worthwhile intervals when the compressor is on and when it is off. However, in the course of modernization, it was established that such a regime provides an adequate flow of cold, but the cold outflow is too small. Causing the freezer pretty quickly (within 2 weeks) is covered by a strong frost, frost. Therefore, while maintaining the specified interval of compressor operation, it became evident the need to increase the 20-minute interval when the compressor is stopped. while providing adjustment of the extent of this increase. This purpose was built an oscillator with two modes of pulse shaping. The level of the log.0. of.1 DD1, as stated above, includes the work of the compressor. He’s using the inverter DD2.1 goes to battery + 15 DD3 that translates in the closed state is included with this IC the analog key. And the main generator begins to produce pulses of minimum duration. providing 20-minute interval of compressor operation. Upon its completion the level of logical state 1. DD1 is reversed. As a result, the compressor stops and an oscillator switches to the mode of formation of pulses with variable duration. Changing the position of the potentiometer R5 is achieved by adjusting this duration, respectively, is adjustable, and the spacing stop of the compressor 20 to. about 33 minutes. The setting of this interval is possible to adjust the medium temperature level in the refrigerator.

Led VD1 in the structure of the scheme is to indicate the state of the electronic switch, upravlaushiy motor. This led glows when the motor is off, and off when it starts to work.

 

The heat relay K1 type RT-10 is used for protection against possible overload on the motor shaft, which, in principle, not excluded in the event of an emergency in the kinematics of the compressor. The presence of this relay breaks the General concept of the proposed modernization, which seeks to free the refrigerator from all mechanical and spring-loaded contacts. However, since this relay is consistently present element in all older units, with extremely rare effect (which keeps a very high resource of his work), it was decided to keep it. The adsorption refrigerators of this element is absent, and therefore the composition of the upgraded scheme it is possible not to include.

 

The first details of domestic production. Capacitor C2 is of type KM-6. Rated power resistors — 0.125 W, except for the resistor R2, the power is 0.25 W. The DC voltage needed to power the electronic elements in the structure of the scheme (10) is a special adapter. As he adapted the adapter for charging mobile phone company MOTOROLA, which consumes a power of about 20 watts. In the case where the electronic switch of the induction motor of the compressor is in the on state, the current load of the adapter will increase the voltage which it generates, is reduced approximately to 6.5 V.

 

Structurally, the circuit is assembled on a printed circuit Board with dimensions of 60×60 mm, containing wiring traces for mounting the electronic component in the mock-up design concepts. It has all the elements of the schema, with the exception of the capacitor C1 and the thermal relay K1, which, due to the considerable size are installed under the bottom of the refrigerator near the compressor unit. The fee represents the second link adapter, MOTOROLA and connected by small lengths of wire (about 10 cm) that serve to supply to the Board the voltage generated by the adaptor, and voltage. The items placed on the Board covered at the top by a plastic cap which is fastened to the Board on Stockach M3 screws. The lid also has a hole for the led VD1 so that it is a fledgling project above the surface of the cover and visible from the outside. On the reverse side of the Board (opposite the side on which smokerboy concept elements), in addition to installation of conductors, carrying her wiring, also installed a regular electrical outlet ХТ1, which is connected to the output epictrance switch that controls the electric motor, and is the cover for the back side of the Board. In the socket is inserted into the saw from the power cable of the refrigerator associated with the capacitor C1 and the terminal of the electric motor of the compressor, and connect the PSU circuit elements into a unified whole. Configuration scheme is not required. If all components of the scheme intact and the connections are correct, the device and the refrigerator work immediately after it is turned on.

 

 

A. CHEREVAN, Saint-Petersburg