The current strength is measured in amperes and characterizes the load of electrical networks. The need to measure the current arises to check whether the load on the cable is permissible. For the installation of electrical wiring, cables of various sections are used. Permissible currents for cables with PVC insulation, laid through the air, are:

If the load of the cable line is exceeded, the cable will heat up, and its insulation will collapse. As a result, this will lead to a short circuit, and the cable will have to be changed to a new one.

Therefore, after replacing the cables, the current flowing through it when all electrical appliances are connected is measured. If the wiring is old, then when connecting an additional load to it, you also need to check whether the currents in it correspond to the permissible values.

At the maximum load of the wiring, you can check whether the current through the circuit breakers corresponds to their ratings. If the rated current of the machine is exceeded, its operation from overload is inevitable.

Current measurement is required to determine the operating modes of electrical appliances. The measurement of the load currents of electric motors is carried out not only to control their serviceability (the currents in all phases must be the same), but also to determine the presence of an overload due to an increased torque on the shaft. For a heater, measuring the current will show whether all the heating elements are working. Only by measuring the load current can you find out if the warm floor has worked.

Electric current power

Power is the work done by an electric current per unit of time. It is measured in Watts (W, W). It is theoretically possible to measure power directly, but special devices are used for this - wattmeters that measure the current through the load and the voltage across it. They give readings in watts, but connecting them is too difficult. Therefore, they are used for measurements in predetermined nodes of the electrical network, connecting to them once and for all.

For domestic use, power is calculated after measuring the current consumed by the load and the voltage across it, which for simplicity can be taken equal to 220 V.

This method does not always give accurate results. If there is an inductive reactance in the load, the active power is affected by the power factor. Some electrical appliances consume non-sinusoidal current (LED and energy-saving lamps, computer and television equipment), which not all measuring instruments designed to measure AC voltage measure correctly.

Instruments for measuring current strength

You can measure the current using the following devices:

— ammeters. Like wattmeters, they are used for stationary measurements.

— multimeter- a multifunctional device with a digital liquid crystal display ();

— tester- a device that measures several quantities, but, unlike a multimeter, has an arrow pointer;

— clamp meter- a device that allows you to measure current without breaking the electrical circuit.

Current measurement methods

Unlike voltage measurement, current is measured not when the device is connected in parallel to the load, but when connected in series. This means that the measuring device must be connected to the break of any of the power wires of a single-phase consumer. With a three-phase power supply, the same must be done for each of the phases. In this case, the current in the neutral wire is not measured, since with a symmetrical load it is equal to zero. Sometimes it is required to measure the current in the neutral conductor, but it is impossible for a group of consumers to turn off zero to make measurements.

All these reasons lead to the fact that testers and conventional multimeters are rarely used to measure current strength. They can only be used for single consumer or DC measurements.

In all other cases, current clamps or multimeters are used that have them in their composition. For measurements, it is enough to open the clamps by pressing the key, place the conductor with the measured current inside the measuring circuit and release the key. The magnetic circuit of the clamps will close and the display (there are clamps with a scale and an arrow) will show the measured value.

When using current clamps, care must be taken to ensure that only the conductor in which the current is measured gets inside the magnetic circuit. When two or more conductors get inside, the clamps will measure the sum of the currents in them, and also the vector one. This means that by placing a two-core cable with a load inside the magnetic circuit of the clamp, we will measure the current equal to zero. Clamps, like RCDs, will add the current flowing through the phase conductor towards the load and the same current with the opposite sign, returning back.

Clamps are intended only for measuring alternating current. At direct current, an attempt to use them will lead to the fact that the magnetic circuit will close with irresistible force. It will not work to unclench it with your hands until the current is turned off.