Starting an Asynchronous Motor with a 230 Volt Single-Phase NetworkA similar thermal effect is caused on the passive resistance. AC voltage is constantly changing, the figure is averaged over time. The result is called the effective( effective) value of the value.
For an asynchronous motor to work properly, the stator field must rotate. Easy to ensure( proven by Nikola Tesla): apply the corresponding phases to the three windings. There is a vector addition of fields. The resulting vector rotates smoothly, drawing the rotor. Efficiency of three-phase motors of a network 380 V maximum from other versions, types of inclusions. In industry, an unusual apartment house is used for voltage. Can a tenant get 380 volts? Hypothetically - yes. A professional electrician will find three phases shifted relative to each other at the desired angle( 120 degrees).
High-rise buildings are powered by a 380-volt network. The apartment gets 1 phase. Rare exceptions are limited to modern high-rise buildings. Some household appliances( cookers) feed on two phases. The measure reduces the requirements for electrical wiring of the apartment.
Phase One. Rotation of the field is impossible in principle. Motion is obtained by folding at least two vectors. It is necessary to use the services of a capacitor, shifting the voltage by 90 degrees. In fact, with the scheme of a star or a triangle, one winding acts as a trigger, makes the field rotate. In the future, the magnitude changes linearly, as the engine has gained momentum, inertia is enough to maintain the rotational motion. Variable field will rhythmically push the rotor in the right direction. Smoothness is inferior to the resultant addition of three vectors, the functioning of home appliances suffices.
Why apartments are devoid of three-phase voltage. Working with him requires deep knowledge, excellent practical skills.230 volts to any housewife will help bring the outlet. One phase and earth( neutral).No need to think. The wording is exaggerated, but close to the meaning of the real state of affairs. We lose efficiency, we get in return simplicity.
What the starting winding does. The engine will not enter the operating mode; it creates the second vector, which in the first approximation makes it possible to consider the field inside the engine rotating. Uneven circle move, spin the rotor enough. The momentum is gained, the start-up coil must be turned off, to the minimum, energy is spent a lot, reducing the efficiency of the device.
The principle of operation of the start-up relay
The start-up coil must be turned off when the revs are turned on. At the time of the start, the windings consume a large current, the effect makes it possible to track the moment of re-switching. The start relay of the refrigerator performs protective functions( not always).The option is implemented by heating the sensitive element with an electric current. Threshold is exceeded - the circuit is broken, regardless of whether the desired mode of the refrigerator has been reached according to the thermostat readings or not. Two schemes of start-up relay operation were invented( at the same time it can be protective):
- "Tablets" work on the basis of a material that is expandable by heating. Initially, the working element is cold, the starting winding consumes current, ensuring a smooth start of the induction motor. Gradually, the temperature of the tablet rises, causing the contact to open, and the work coil remains on. We believe that in order to maintain the mode inside the relay, a mechanism preventing the cooling of the tablet is installed. Working winding choke, heating element. If the tablet relay breaks, often inside you can hear the rustle of scattered powder, changing the position of the instrument housing.
- Induction relays are based on the action of electromagnets. When starting, the current is large and due to this, the core presses the contacts of the starting coil. Over time, engine consumption drops. As a result, the current does not balance the spring, the contacts of the starting coil open. Note: it is important to orient the relay in space correctly. Often the core falls, carried away by the force of force. On the other hand, it is much easier to test such elements: turn from side to side so that the contacts of the starting relay change the resistance from zero to infinity.
With tablets, thermal relays on a bimetallic plate often go in one case. A current of the working coil passes through it. As soon as the value exceeds the threshold, the contacts open, stopping the compressor. The bimetallic refrigerator type relay circuit is based on the heating of the sensing element. There is nothing difficult! Two plates are welded to each other tightly. The coefficient of expansion of metals in them is different. When heating occurs, the double plate bends toward the material, which is less elongated. It becomes possible to trigger the relay. This scheme is often used home appliances.
A heating coil is often used in induction relays. Here the material is already one. But heats( !) The bimetallic plate. Through the coil passes the current of the working coil. If the amperage is too large, then the bimetallic plate breaks the contacts. The induction start-up relay has the following types of malfunctions:
- has blown the coil, in this case the contacts will not ring in any position;
- jammed core, the engine does not start, or the engine stalls after 5 - 10 seconds;
- plate mode is broken, the refrigerator is turned off even in normal mode.
We want to pay attention: thermal protection is completely emergency. In normal operation, the relay should not operate. At the same time, the starting function accompanies the refrigerator for a period of operation. The switching process is accompanied by a slight click. Start-up relay in the refrigerator is often heard when the device is working.
Design of the start-up relay
The start-up relay resembles the appearance of a tablet or an indefinite form. This is such a small element, located directly next to the black barrel-shaped housing of the compressor. Have you ever wondered why this color of soot was chosen by the coloring of the heart of the refrigerator?
The answer is simple: black absorbs heat, but also radiates well. In which direction the process moves, determines the direction of the temperature difference between the compressor and the environment. When the motor is hot, the black case gives off heat to the air. In addition, there is a fan nearby that creates forced compressor cooling.
Switching circuit for start-up relay of the refrigerator:
- Phase 220 V.
- Starting winding of an asynchronous compressor motor.
- Working winding of an asynchronous compressor motor.
Usually you can find out what connects to where and by the color of the wires. In any case, repairs should be carried out carefully. It is easier to find out the compressor ground, if you scrape a little paint off the case, ring three contacts. But this method is left finally, when the rest did not help.
Induction starting protection relays DHR are mounted on a fixed frame and work in tandem with DCM compressors. After the designation may be a number that is the same for both devices. The difference in the design of the operating voltage and the currents of operation and release. To accelerate the breaking of the chain in case of overheating, a magnet is located behind the bimetallic plate. If the metal enters the field of action, then the response of the system is accelerated. The magnet also serves to hold the bimetallic plate with an open contact a little longer than is necessary to normalize the temperature. This is an additional protective measure.
The induction relay of the RTP refrigerator compressor differs in that it can be on the wire. It is not necessary to attach to the frame. Work is carried out with compressors DHM 3 and 5. The difference from DHR in a somewhat lower response current. This will protect the compressor more reliably. The release current is the same. Craftsmen use refrigeration compressors, making high-pressure apparatuses, receivers. Pumped tires, use pneumatic equipment.
Before you buy a relay for a refrigerator, make sure that the product matches the type of compressor. Then the item must be properly installed. It is better to take exactly the brand that was before the repair. If the relay of the Biryusa refrigerator is equipped with a type of RTK, it is better to take this, despite the fact that RTP and DHR are also suitable for the DHM engine. Device compatibility will help determine reference tables. Indicate the necessary technical information.