Asynchronous electric motors are more common than others in production and are often found in everyday life. With their help, various machines are driven: turning, milling, grinding, lifting mechanisms, such as an elevator or crane, as well as various kinds of fans and hoods. This popularity is due to the low cost, simplicity and reliability of this type of drive. But it happens that a simple technique breaks down. In this article, we look at typical malfunctions of squirrel-cage induction motors.

Faults can be divided into three groups: the engine heats up, the shaft does not rotate or does not rotate normally, it makes noise, vibrates. In this case, the engine housing can be completely heated or some separate place on it.And the motor shaft may not budge at all, not develop normal speed, its bearing may overheatand, make abnormal sounds for his work, vibrate ...

Today we’ll talk about something that many electricians who make wiring in apartments did not even hear about, but every day electrical workers in enterprises or organizations deal with this. When they are sent to carry out some types of tasks, they are preliminarily given an admission order for work in electrical installations. We will talk about what it is later in the article.

One of the main documents for an electrician is PBEEP or the Rules for the Safe Operation of Electrical Installations of Consumers. On it annually, and in the event of a break in work for more than 6 months or other situations, they often pass exams to obtain an electrical safety clearance group. Let's look at what is written in it, below is a screenshot from the text of this document. Admission order (outfit) - an order for the safe conduct of work drawn up on a special formdefining its content, place, start and end time ...

Thermocouples exist due to such a phenomenon as contact potential difference. If two different solid conductors or semiconductors are brought into close contact with each other, then separated electric charges are formed in the vicinity of the place of their contact. In this case, at the external ends of these conductors a potential difference will occur. This potential difference will be equal to the difference in the work function for each metal divided by the electron charge.

It is clear that if you close such a pair into a ring, the resulting EMF will be zero, but if on the one hand it is still left open, then there will be a real EMF, ranging from tenths of a volt to units of volts, depending on what this is for the materials. Of course, it is not possible to measure the contact potential difference with a voltmeter, however, it will show itself on the current-voltage characteristic, for example, it manifests itself in the transistor and in the diode at the p-n junction ...

Asynchronous motors are motors in the process of which under load a phenomenon of sliding is observed, that is, a “lag” of the rotor rotation from the rotation of the stator magnetic field. In other words, the rotor rotates not synchronously with the rotation of the stator magnetization, but asynchronously with respect to this movement. That is why these types of motors are called asynchronous (non-synchronous) motors.

In most cases, pronouncing the phrase “asynchronous motor”, they mean the brushless AC motor.The slip value of an induction motor can be different depending on the load, as well as on the power parameters and the method of controlling the stator winding currents. If we are dealing with a conventional AC motor, like AIR712A, then with a synchronous frequency of rotation of the magnetic field of 3000 rpm, under conditions of nominal mechanical load ...

If we take a brand-new lithium-ion battery, let's say size 18650 with a nominal capacity of 2500mAh, bring its voltage to exactly 3.7 volts, and then connect it to an active load in the form of a 10-watt resistor with a value of R = 1 Ohm, then what is the constant current we expect to measure through this resistor?

What will happen there at the very first moment of time, until the battery almost starts to discharge? In accordance with Ohm's law, it would seem that there should be 3.7A, since i = U / R = 3.7 / 1 = 3.7 [A]. In fact, the current will be slightly less, namely, in the region of I = 3.6A. Why is this going to happen? The reason is that not only the resistor, but the battery itself has some internal resistance, since the chemical processes inside it cannot occur instantly. If you imagine a battery in the form of a real two-terminal, then 3.7V - this will be its EMF ...

If you think hard, then all kinds of applications for such a seemingly simple thing as an inductor simply can not be counted. In one article, we recall only a few of them. Meanwhile, human ingenuity and talent do not tire of creatively expressing themselves by inventing and developing more and more new devices and mechanisms based on inductors.

It would seem that here you can build? A simple coil of wire, it can be a core of a certain shape, and the current passing through the wire in a constant, variable or pulsed form. And yet, without inductors, all modern electrical engineering simply could not exist. Let's take a closer look. Elevator washers have been used worldwide for many years to load ferromagnetic waste. The electromagnet just clings to a crane hook ...

In production and in everyday life, automation is actively used. For this, actuators of various types are used, hydraulic, pneumatic and electric. Such devices include, disable, change the mode of operation of mechanisms, systems and devices. In this article we will look at some electromagnetic actuators.

To propel various mechanisms using electric motors and electromagnetic actuators. For example, electric motors are used for automatic or semi-automatic control of valves, the so-called shutoff valves on pipelines, like gas, pneumatic, water supply and other. The principle of operation of an electromagnetic actuator is to perform a magnetic field to move the core associated with actuators ...

The thermal relay performs the function of protecting against prolonged overloads, their operation is similar to the operation of the thermal disconnector in circuit breakers. Depending on the magnitude of the overload (deviation from the nominal mode - I / Iн), it is triggered after an appropriate period of time, which can be calculated from the time-current characteristic of the thermal relay. Let's take a closer look at what a thermal relay is and how to choose it correctly.

When the motors are overloaded, the current consumption increases, and its heating increases accordingly.If the engine overheats, the integrity of the insulation of the windings is violated, the bearings wear out faster, they can jam. In this case, the thermal release of the machine may not protect the equipment. To do this, you need a thermal relay. Overloads can occur due to phase imbalance, obstructed movement of the rotor, due to both increased mechanical load ...