[Transformer parameters] What are the transformer parameters? Complete list of main parameters of transformers
Introduction to transformers
Transformers are devices that use the principle of electromagnetic induction to change AC voltage. The building blocks are the primary coil, the secondary coil and the core (magnetic core). In electrical equipment and wireless circuits, it is often used to increase and decrease voltage, match impedance, safety isolation, etc. According to their uses, transformers can be divided into distribution transformers, power transformers, fully sealed transformers, combined transformers, dry-type transformers, single-phase transformers, electric furnace transformers, rectifier transformers, reactors, anti-interference transformers, lightning protection transformers, box type transformer, test transformer, corner transformer, high current transformer and excitation transformer.
Principle of Transformer
A stationary device that uses the principle of electromagnetic induction to transfer electrical energy or electrical signals from one circuit to another. Transformers in electronic circuits are mainly used for voltage amplitude conversion and impedance matching conversion of circuit loads. It consists of a primary winding (primary winding) and a secondary winding (secondary winding) wound around an iron core. The working voltage ranges from millivolt level to kilovolt level; the output power ranges from milliwatt level to kilowatt level; the working frequency ranges from tens of Hz to radio frequency; in addition to sine waves, waveforms also include rectangular waves, pulse waves and various complex waveforms. . In addition to general power transformers, commonly used transformers include audio transformers, impedance matching transformers, pulse transformers, video transformers, radio frequency transformers, etc.
What are the transformer parameters?
Different types of transformers have corresponding technical description requirements, which can be represented by corresponding technical description parameters. For example, the main technical parameters of power transformers are: rated power, rated voltage and voltage ratio, rated frequency, operating temperature level, temperature rise, voltage regulation rate, insulation performance and moisture-proof performance. The main technical parameters of general low-frequency transformers are: Transformation ratio, frequency characteristics, nonlinear distortion, magnetic shielding and electrostatic shielding, efficiency, etc.
The main parameters of the transformer include voltage ratio, frequency characteristics, rated power and efficiency, etc.
1. Voltage ration
Voltage ratio of transformerThe relationship between n and the number of turns and voltage of the primary and secondary windings is as follows:n=V1/V2=N1/N2WhereN1 is the primary (primary) winding of the transformer, N2 is the secondary (secondary) winding,V1 is the voltage across the primary winding, V2 is the voltage across the secondary winding. The voltage ratio of the step-up transformern is less than 1, and the voltage ratio of the step-down transformern is greater than 1, and the voltage ratio of the isolation transformer is equal to 1.
2. Rated powerP
This parameter is general For use in power transformers. It refers to the output power of the power transformer when it can work for a long time without exceeding the specified temperature under the specified operating frequency and voltage. The rated power of the transformer is related to the core cross-sectional area, enameled wire diameter, etc. The transformer has a large core cross-sectional area and a thick enameled wire diameter, and its output power is also large.
3. Frequency characteristics
Frequency characteristics mean that the transformer has a certain operating frequency range. Transformers with different operating frequency ranges generally cannot Used interchangeably. Because the transformer operates outside its frequency range, the temperature may rise during operation or the transformer may not work properly.
4. Efficiency Efficiency
refers to the ratio of the transformer output power to the input power at rated load. . This value is proportional to the output power of the transformer, that is, the greater the output power of the transformer, the higher the efficiency; the smaller the output power of the transformer, the lower the efficiency. The efficiency value of the transformer is generally between 60% and 100%.
At rated power, the ratio of the output power and input power of the transformer is called the efficiency of the transformer, that is,
η=x100%
Whereη is the efficiency of the transformer ; P1 is the input power, P2 is the output power.
When the output power of the transformer P2 is equal to the input power P1, the efficiency η is equal to 100%, the transformer will not produce any losses. But in fact there is no such transformer. Transformers always produce losses when transmitting electrical energy, and these losses mainly include copper losses and iron losses.
Copper loss refers to the loss caused by the resistance of the transformer coil. When current passes through the coil resistance and heat is generated, part of the electrical energy is converted into heat energy and is lost. Since the coil is generally made of insulated copper wire, it is called copper loss.
The iron loss of the transformer includes two aspects. One is hysteresis loss. When alternating current passes through the transformer, the direction and size of the magnetic field lines passing through the silicon steel sheet of the transformer change accordingly, causing the molecules inside the silicon steel sheet to rub against each other and release heat energy, thereby losing part of the electrical energy. This is hysteresis loss. . The other is eddy current loss when the transformer is working. There are magnetic lines of force passing through the iron core, and an induced current will be generated on a plane perpendicular to the magnetic lines of force. Since this current forms a closed loop to form a circulating current and becomes a vortex, it is called an eddy current. The existence of eddy current causes the iron core to heat up and consume energy. This loss is called eddy current loss.
The efficiency of the transformer is closely related to the power level of the transformer. Generally, the greater the power, the smaller the loss and output power, and the higher the efficiency. On the contrary, the smaller the power, the lower the efficiency.
How to read parameters from the nameplate
Under the specified use environment and operating conditions, the main technical data of the transformer are generally marked on the nameplate of the transformer. It mainly includes: rated capacity, rated voltage and taps, rated frequency, winding connection group, rated performance data (impedance voltage, no-load current, no-load loss and load loss) and total weight.
A, rated capacity (kVA): rated voltage. The capacity that can be delivered when running continuously under rated current.
B, rated voltage (kV): the working voltage that the transformer can withstand when running for a long time. In order to adapt to the needs of grid voltage changes, the high-voltage side of the transformer has taps, and the low-voltage side output voltage is adjusted by adjusting the number of high-voltage winding turns.
C, rated current (A): The current that the transformer is allowed to pass for a long time under the rated capacity.
D, no-load loss (kW): When the rated voltage at rated frequency is applied to the terminals of a winding On, the active power absorbed when the remaining windings are open circuit. It is related to the performance and manufacturing process of the core silicon steel sheet, and the applied voltage.
E, no-load current (%): The current flowing through the primary winding when the secondary side of the transformer is no-loaded at rated voltage. Generally expressed as a percentage of rated current.
F, load loss (kW): short-circuit the secondary winding of the transformer and tap the rated tap on the primary winding The rated current is passed through the position, and the power consumed by the transformer is at this time.
G, impedance voltage (%): Short-circuit the secondary winding of the transformer, and slowly increase the voltage in the primary winding. High voltage, when the short-circuit current of the secondary winding is equal to the rated value, the voltage applied to the primary side at this time. Generally expressed as a percentage of rated voltage.
H, phase number and frequency: three-phase starts with S, single-phase starts with D means. China’s national standard frequency f is 50Hz. There are 60Hz countries abroad (such as the United States).
I, temperature rise and cooling: The difference between the temperature of the transformer winding or upper oil and the temperature of the surrounding environment of the transformer is called the temperature rise of the winding or upper oil surface. The temperature rise limit of oil-immersed transformer windings is 65K, and the oil surface temperature rise is 55K. There are also many cooling methods: oil-immersed self-cooling, forced air cooling, water cooling, tube type, chip type, etc.
J. Insulation level: There are insulation grade standards. Examples of how to express the insulation level are as follows: the high voltage rated voltage is 35kV level, the low voltage rated voltage is 10kV level The insulation level of the transformer is expressed as LI200AC85/LI75AC35, where LI200 means that the high-voltage lightning impulse withstand voltage of the transformer is 200kV, power frequency withstand voltage is 85kV, low voltage lightning impulse withstand voltage is 75kV, power frequency withstand voltage is 35kV.
K, connection group label: according to transformer 1. The phase relationship of the secondary windings connects the transformer windings into various combinations, which are called connected groups of windings. In order to distinguish different connection groups, clock representation is often used, that is, the phasor of the high-voltage side line voltage is used as the long needle of the clock and is fixed on 12, and the phasor of the low-voltage side line voltage is The phasor is used as the short hand of the clock. Which number the short hand points to is used as the label of the connection group. For example, Dyn11 means that the primary winding is a (triangular) connection, the secondary winding is a (star) connection with a center point, and the group number is (11) points.
If the website content violates your rights, please contact us to delete it。
