Beginners ask what inverter air conditioner is, why it is needed. Dive deep into the theory. This will help to understand why engineers are fighting for years on new technical solutions. The bare words that the inverter motor is quieter and saves energy no longer entice the consumer. I want to know what are capable of air conditioners, equipped with the latest technology. Taking as a basis the course of lectures of a famous St. Petersburg educational institution, let us present the knowledge that is not yet available even in Wikipedia. Rate it!
Why do we need
inverter systemFifty-year-old textbooks mention that the thyristor pulse shaper method for switching windings is promising. The specified electronic unit is busy forming phases for switching valves. The rotor position sensor tells the air conditioner brain where to feed the impulses.
The AC voltage is rectified and then cut into pulses, the frequency of which directly affects the speed of rotation of the shaft. Came to the opening gradually. Readers have noticed, of course, that collector motors are often used in electric tools, and asynchronous are more common in industry. We will reveal the reasons.
Advantages of collector and asynchronous motors
Collector engines independently, without additional modifications, have significant starting torque. This is a natural quality, which makes it possible to move a load from a place even at low revs. With increasing frequency torque torque falls, which is considered normal. Moreover, the dependence on rotation is linear. Collector motors like home appliance makers for ease of adjustment.
By simply varying the amplitude of the supply voltage, you can vary the speed over a wide range. The dependence is linear, which greatly simplifies the design. In addition, there are thyristor circuits for automatic stabilization of revolutions depending on the magnitude of the arcing, which is used in practice. The reasons for the selective use of collector engines:
- The collector engines have a great need for human attention. You will have to maintain the brushes frequently. Graphite is fragile. As a result, for an air conditioner designed to work day and night, this solution is not effective.
- Finally it makes it impossible to use a high level of noise from devices using a collector motor. It is simply impossible to work, read, live next to a roaring external air conditioner unit. Rumbles like a tractor, in addition to the heavy physical atmosphere, violating the laws of silence and tranquility of citizens. Listen, modern air conditioner noise is much weaker than a vacuum cleaner, where there is a collector engine.
- Collector engines do not tolerate aggressive environments. In our nature with acid rain, the latter is relevant.
- By design, collector engines are unable to provide high speeds. The limit is visible in centrifugal juicers. Maximum 40 thousand revolutions per minute.
On the other hand, asynchronous motors in their original form have a weak starting characteristic. This is a high current in the first fraction of a second and low torque at the start. Features even below nominal. In an air conditioner compressor, where the start is already difficult, the use of such devices is simply irrational. These deficiencies were trying to fix.
For example, the construction of a double squirrel cage is being introduced, when at the start field both layers of conductors are captured due to the low rotational speed, then the induction currents are pushed to the surface. There are techniques for increasing the active resistance of stator conductors, due to which more power is allocated there. It turns out, the characteristic load is straightened, but the operational properties deteriorate: losses grow, intensive cooling is required. There is no question of saving.
It turns out, asynchronous motors are quiet, unpretentious in operation, only lubrication of bearings is required. It maintains the mechanism of high speeds well, but is simply not suitable for use in external units of air conditioners. In addition, the increase in the active resistance of the rotor sharply worsens the adjustment characteristic. The situation is a dead end, we need a completely new technology to overcome the limitations of the old types of engines. These are inverter motors - an attempt to eat a fish, and not to choke on a bone.
Inverter motors for
air conditioners Scientists have come to the conclusion that it is necessary to combine the advantages of ease of adjustment and high starting torque of a collector motor with low losses, excellent heat dissipation conditions, and the absence of fragile and unnecessary moving parts of synchronous motors with a permanent magnet rotor. A description of the inverter technology. Already brought the scheme of work from an electrical point of view, today they plunged readers into mechanics.
Note. Recall that a synchronous motor is called, where the voltage is simply applied to the winding in its original form, and the rotor fulfills the frequency of the incoming current. This is a simple and easy-to-understand type of engine.
The only foreseeable disadvantage of this design is called the breakdown of speed up to a complete stop with an uncontrolled increase in load. However, inside the inverter air conditioner, the situation was considered abnormal, and the mode should not be taken as a limiting factor for the use of this type of engine. The synchronization of the voltage supply to the desired winding is regulated by the rotor position sensor. The level that determines the speed of rotation is determined by the pulse repetition rate. With a decrease in the duty cycle, the constant component grows. Briefly described inverter air conditioner.
The described technique is called pulse width modulation. Essence: the duration of the peaks vary according to need. The wider the pulses( the period remains the same), the greater the constant component of the spectrum, the higher the number of rotor revolutions.
Switching with brushes is not the best option, because mechanically rubbing parts are always considered a weak link and at the same time increase the level of noise and vibrations, causing sparking. These factors tend to avoid. In addition, we need a circuit designed to form control pulses in the inverter air conditioner. An electronic unit has been created for the result.
The motor differs little from the synchronous one, the windings are switched by electronics. These are key elements like:
The pulses are cut in batches continuously under the action of a clock generator, but which of the outputs( read, the motor stator winding number) receives a signal, decides the smart switching circuit, which is guided by the rotor position sensor. Notice that if there is an intelligent control module, the difficulty of starting the equipment disappears. In synchronous motors there is a certain position of the rotor, where the field does not capture the magnetic moment of the shaft. If there are many windings on the stator( instead of one or two pairs) and the position sensor, the situation changes drastically. Due to the foregoing, difficulties with starting the inverter air conditioner compressor disappear.
It is shown that such engines have a number of advantages: good cooling conditions, low losses, the absence of unnecessary moving parts, simplicity and low cost of manufacture. Inverter air conditioner is expensive - you need to attach the control module to the engine. Electronics and gaining a difference in price compared to the previous generation.
We believe that now readers understand what an inverter air conditioner is, why it is needed. We emphasize that we have already published an extended review on the subject of Mitsubishi climate technology, where they explained the evolution of technology. It shows how the design, form, and efficiency of the control voltage progressed and changed. A byproduct were multiple interesting features that ensured considerable demand for this type of product.
We are grateful to the St. Petersburg teachers for the quality course of lectures, we believe that the information is interesting for readers.