The role of mutual inductor

The role of mutual inductor

The role of voltage transformer

The function of the voltage transformer is to convert the high voltage into a standard secondary voltage of 100V or lower in proportion for use in protection, metering, and instrumentation. At the same time, the use of voltage transformers can isolate high voltage from electrical workers. Although the voltage transformer is also
a device that works according to the principle of electromagnetic induction, its electromagnetic structure is exactly the opposite of that of the current transformer. The secondary circuit of the voltage transformer is a high-impedance circuit, and the magnitude of the secondary current is determined by the impedance of the circuit. When the secondary load impedance decreases, the secondary current increases, causing
the primary current to automatically increase by one component to meet the electromagnetic balance relationship between the primary and secondary sides. It can be said that the voltage transformer is a special transformer with a limited structure and form of use.

Voltage transformer is an indispensable electrical appliance in power transmission and power supply systems such as power plants and substations. Precision voltage transformer is an instrument used in electrical test laboratories to expand the measurement limit and measure voltage, power and electric energy.

Voltage transformers are very similar to transformers, both of which are used to transform the voltage on the line. However, the purpose of transformers to transform voltage is to transmit electric energy, so the capacity is very large, generally calculated in kilovolt-amperes or megavolt-amperes; while the purpose of voltage transformers to transform voltage is mainly to power measuring instruments and relay protection devices, to measure the voltage, power and electric energy of the line, or to
protect valuable equipment, motors and transformers in the line when a line fault occurs. Therefore, the capacity of voltage transformers is very small, generally only a few volt-amperes or tens of volt-amperes, and the maximum does not exceed one thousand volt-amperes.

Why do we need to change the voltage on the line? This is because the voltage on the line varies greatly according to the different situations of power generation, transmission and power consumption. Some are low voltage 220V and 380V, and some are high voltage tens of thousands of volts or even hundreds of thousands of volts. To directly measure these low and high voltages, it is necessary to make corresponding low and high voltage voltmeters and other instruments and relays according to the size of the line voltage
. This will not only bring great difficulties to the instrument production, but more importantly, it is impossible to directly make high-voltage instruments and measure voltage directly on high-voltage lines. It is absolutely not allowed.

If a voltage transformer is connected to the line to transform the voltage, the low and high voltages on the line can be uniformly converted into one or several low voltages according to the corresponding proportions. By using one or several voltage specification instruments and relays, such as a general voltage of 100V, the voltage on the line can be measured and monitored through the voltage transformer.

The role of current transformer

The current transformer converts large current into small current according to a certain ratio, provides current for various instruments and relay protection, and isolates the secondary system from high voltage. It not only ensures the safety of people and equipment, but also simplifies and standardizes the manufacture of instruments and relays, and improves economic benefits.

Generally, it is used in conjunction with an ammeter. Its main purpose is to use a small ammeter to measure a large current. The primary side is connected to the measured circuit, and the secondary side is connected to the ammeter. When wiring, pay attention to the range, that is, the maximum measurement range of the ammeter. It also needs to be grounded.