For starting, reversing, forcibly stopping countercurrent asynchronous electric motors, electricians use contactors and magnetic starters. The reliability of the system as a whole, as well as the electrical safety of the service personnel, depend on the correct choice of switching equipment.

Choosing a starter and excess switching current leads to large financial costs, when it is switched, flip flops of a higher volume are heard than those produced by small starters. Inadequate switching power starters will not last for a long time, they will warm up, and burn terminal blocks and contacts. As a result, the transition resistance of the contact will increase until the contact disappears completely, which will lead to premature replacement of the device. Circuit breakers must also be correctly selected, especially when starting the engine hard ...

The relay has a limited resource, this is primarily due to the principle of its operation: the electromechanical relay operates due to the magnetic field and the closure of mechanical contacts. Mechanical contacts wear out, the coil burns out, hence the need for repair. Most often, the repair consists in cleaning the contacts or solving problems with the coil.

Before moving on to repair issues, let's walk through the components of an electromagnetic relay. The relay itself compares the magnitude of the control action, after which the signal is transmitted to the controlled circuit. In our case, an electric current is supplied to the coil. The anchor is attracted to the core of the coil due to the magnetic force created by the magnetic flux. The relay is triggered if sufficient voltage and current are supplied. When the electromagnet trips, the contacts close ...

Switching is turning the appliance on or off in the network. To do this, use disconnectors, switches, circuit breakers, relays, contactors, starters. The last three (relays, contactor and magnetic starter) are similar in structure, but are designed for different load capacities. These are electromechanical switching devices.

To turn on the load, you need to apply voltage to its conclusions, it can be constant and variable, with a different number of phases and poles. The voltage can be applied in several ways: a detachable connection, a disconnector, through a relay, a contactor, a starter or a semiconductor switching device. The first two methods are limited both by the maximum switching power and by the location of the connection point. This is convenient if you turn on the light or the device with a switch or an automatic machine ...

In most automation circuits and control circuits, limit switches are used - this is an apparatus for switching an electric circuit through the action of an actuator on it. They are sometimes called limit switches. They are used in automatic electric drive devices, burglar alarm systems and other devices. We will consider a typical application in this article, we will begin from simple to complex.

I decided to start the article with what most ordinary people saw. If few people work with lathes, elevators and hoisting cranes, then everyone faced cars. The first thing that comes to mind is the limit switch, signaling an open door.In classic domestic cars, it was used to turn on interior lighting (ceiling lamp) ...

For beginners, electronics engineers, it is important to understand how the parts work, how they are drawn on the circuit and how to understand the electrical circuit diagram. To do this, you first need to familiarize yourself with the principle of operation of the elements, and how to read electronics circuits I will describe in this article on examples of popular devices for beginners.

A diagram is a diagram in which, with the help of certain symbols, the details of a diagram are depicted, lines are their connections. Moreover, if the lines intersect, then there is no contact between these conductors, and if there is a point at the intersection, this is the junction of several conductors. In addition to icons and lines, the diagram depicts letter symbols. All designations are standardized, each country has its own standards, for example, in Russia they adhere to the standard GOST 2.710-81. Schemes do not always read from left to right and from top to bottom ...

It is necessary to consider this topic from magnetic starters from representatives of the Soviet era. Bright representatives are PML and the like. Starters are used to switch a powerful load with a control signal with a small current. The control signal is supplied to the coil, which creates a magnetic field. It, in turn, creates a force on the magnetic circuit, which is mechanically connected with moving power contacts and block contacts.

The magnetic starter can be divided into two parts: upper and lower. In the lower part there is a coil and a fixed part of the magnetic circuit, terminal terminals of the coil. The upper part of the starter contains: a set of contacts, a moving part of the magnetic circuit with a return spring. It is needed to open the contacts, when voltage is not applied to the coil, the contacts return normal position. On many copies it is located ...

If the phase and zero of the electric network are connected to each other under voltage, not directly through the consumer, but directly, then a short circuit will occur, short for short circuit. Short circuit is the connection of the conductors of the individual phases to each other or to the ground through a relatively low resistance, which is assumed to be zero with a dead metal short circuit.

No network is designed for continuous operation in this mode. However, this emergency mode sometimes occurs. So, a short circuit can occur due to a violation of the insulation of the wiring or due to an accidental short circuit of unlike conductors by the conductive parts of the electrical equipment. Normal operation of the electrical network will be disrupted. To prevent this undesirable phenomenon, electricians use terminal blocks or simply isolate the connections ...

The electrician in his practice is faced with completely different cases, which sometimes reach the point of absurdity. After all, you can never foresee what might happen to electrical equipment during its operation. Equipment is three-phase and single-phase - these types are most common.

However, it is worth noting that their breakdowns are either the same or have similar causes. The most common element in the electrical equipment of an industrial enterprise was and remains (perhaps forever) an electric motor, let's look at the causes of their breakdowns. Problems with electric motors. Situation: voltage comes to the electric motor, but it does not work or does not work properly. Start inspecting the boxes on the motor housing where the cable is supplied and disconnecting the star or triangle circuit. Oxidation or burning of contacts.You need to clean them and make a trial run ...