Asynchronous motor, the principle of operation - there is nothing easier ...
The word "engine" always generates a representationsomething mobile, and even more often - rotating. Of course it's because the engine. The essence of any engine is to transform some kind of energy into motion. Do you know which engine was the first? It is believed that it was a sail. It will not be a mistake to say that the most common engine is electric. Among all the variety of electric machines of this class, the greatest use has been made of an asynchronous motor, the operation principle of which is based on the use of two fundamental manifestations of electric energy - electromagnetism and electrical induction.
To understand the principle of operation of an asynchronous electric motor, let us recall the simplest experiments from the school course of physics:
- if a current flows through a conductor, a magnetic field proportional to the current arises around it;
- if we take two conductors with a current, then between them there is a force field - they repel or attract, just like any pieces of magnets do;
- if one conductor with current moves relative to another, which is not connected to the source, but its circuit is closed, then a current appears in it.
Physical, or, more precisely, speculative,The process model includes the concept of magnetic lines of force, by which we denote the presence of magnetic properties. Here they are and stretch their "tentacles" in all directions, and if a ferromagnetic material is encountered on the way, i.e. such that the magnetic lines are concentrated, then the driving force acts on it. And if this material itself is a magnet, then the force interaction of the magnetic fields is manifested even more. The magnetic field of the conductor can be increased by winding a large number of turns onto a rod made of a ferromagnet; in the simplest case, this is an ordinary metal cylinder made of ferrous metal. It is quite easy to make a rod like a horseshoe, and put a winding on it. The ends of the "horseshoe" became the poles of the magnet, which, when the current is turned on through the coil, will create a powerful, maximum center of the poles, a magnetic field. Usually we visualize it in the drawings with lines.
If the gap between the poles is placeda metal rod, and then start rotating our magnetic "horseshoe", then notice that the rod will also rotate. Why is our device called an induction motor? The principle of operation of this electric machine, as has been said, relies on the phenomenon of electromagnetic induction, i.e. crossing the magnetic lines of the inductor of the body of our rod. And the "intersection" is possible only when the speed of rotation of the magnetic field of the inductor - the "horseshoe" - is greater than the rotation speed of the rod. This motor parameter - asynchronous speed of rotation - is called "slip" and can reach up to 7% of the rated speed of the stator magnetic field.
The maximum of the magnetic field in the gap"Horseshoe", changes its spatial position when it is turned. In accordance with the law of electromagnetic induction, an electric current appears in the rod together with its "life companion" - a magnetic field. Magnetic fields adhere, interact, and ... rotate the rotor. The real asynchronous motor repeats the principle of operation exactly as described here. Everything, the circle is closed - we have two objects without a mechanical connection, but the rotation of one of them, which receives electrical energy, leads to the rotation of the other. The role of the invisible "rope" is performed by the magnetic fields of the horseshoe magnet and rod.
To create an engine, there is almost nothing left- you do not need to rotate the "horseshoe", but make the magnetic field rotate yourself. In other words, the principle of operation demonstrates the principle of operation by the fact that in it the point of maximum of the magnetic field moves in a stator in a circle, as if it is our rotating electromagnet. It remains to work for a small one - to "twist" the magnetic field.
The problem of a rotating magnetic field is solved as follows:
- on the circle have three pairs of poles - coils - at an angle of 120 degrees;
- each coil is energizedsinusoidal form from a separate source. It is believed that the full time cycle of the sinusoid (period) is 360 degrees. A positive voltage maximum occurs 90 degrees after a zero value-everything as taught in the school;
- The highlight is that the voltage maximacome with a time shift of a third of the period (electricians say "three phases with a shift of 120 degrees") - this is the principle of the asynchronous motor. The maximum of the magnetic field strength moves from the first pair of poles to the second, and then to the third. Then the process repeats, which is equivalent to the displacement, more precisely, the "rotation" of the magnetic field.
Just like that, simply and without noise, electric energyThe stator turns into a mechanical motion of the rotor. To create this miracle engine, humanity took several decades, and we had 15 minutes to confidently say: an asynchronous motor? Nothing is easier.