The principle of transformer, the working principle of transformer

In the AC circuit, the equipment that increases or decreases the voltage is called a transformer, and the transformer can convert any value of voltage into the voltage value we need at the same frequency to meet the requirements of power transmission, distribution and use. For example, the voltage level of electricity generated by power plants is low, and the voltage must be increased to be transmitted to distant power consumption areas, and the power consumption areas must be reduced to suitable voltage levels to supply power equipment and daily electrical equipment. Transformers are made based on electromagnetic induction.

It consists of an iron core stacked with silicon steel sheets (or silicon steel sheets) and two sets of coils wound around the iron core, and the iron core and coils are insulated from each other without any electrical connection, as shown in the figure. We call the coil connected between the transformer and the power supply side as the primary coil (or primary side), and the coil connected between the transformer and the electrical equipment as the secondary coil (or secondary side). When the primary coil of a transformer is connected to an AC power source, changing magnetic field lines are generated in the core.

Since the secondary coil is wound on the same core, the magnetic field line cuts the secondary coil, and the induced electromotive force must be generated on the secondary coil, so that the voltage appears at both ends of the coil. Since the magnetic field lines are alternating, the voltage of the secondary coil is also alternating. And the frequency is exactly the same as the mains frequency.

It has been theoretically confirmed that the voltage ratio of the primary coil to the secondary coil of the transformer and the ratio of the number of turns of the primary coil to the secondary coil are related, which can be expressed by the following formula: primary coil voltage Secondary coil voltage = number of turns of primary coil Number of turns of secondary coil Indicates that the more turns, the higher the voltage. Therefore, it can be seen that the secondary coil is less than the primary coil, which is the step-down transformer.

The opposite is a step-up transformer.

The basic principle of this transformer:

1. Use a transformer to reduce the 220V AC voltage to about 3 6 9V;

2. Use a bridge rectifier to convert the reduced alternating current into direct current (pulsating), and use a filter capacitor to filter out the AC component in the pulsating direct current to obtain a relatively stable DC voltage.

A transformer with a 220V input and a tap is used to obtain 1 AC voltage of 3V, 6V, and 9V, respectively, and a gear switch is used to tap them to the common rectifier filter circuit. The output voltage can be adjusted by adjusting the gear switch.

This power source is a transformer. The 220V alternating current is converted into the required low-voltage electricity, and then rectified into direct current for use by electrical appliances.

Isn't it electromagnetic induction, junior high school students know it!!

Electromagnetic Induction.

Principle of electromagnetic induction. The transformer has two sets of coils, of which the winding connected to the power supply is called the primary coil, and the rest of the windings are called the secondary coil, and the secondary coil is outside the primary coil. When the primary coil is connected with alternating current, the transformer core generates an alternating magnetic field, and the secondary coil generates an induced electromotive force.

Transformer Characteristic Parameters:

1. Working frequency.

The core loss of the transformer has a great relationship with the frequency, so it should be designed and used according to the frequency used, which is called the working frequency.

2. Rated power.

At the specified frequency and voltage, the transformer can work for a long time without exceeding the output power of the specified temperature rise.

3. Rated voltage.

Refers to the voltage allowed to be applied on the coil of the transformer, which shall not be greater than the specified value when working.

4. Voltage ratio.

It refers to the ratio of the primary voltage and the secondary voltage of the transformer, and there is a difference between the no-load voltage ratio and the load voltage ratio.

5. No-load current.

When the transformer is secondary open, there is still a certain amount of current in the primary, and this part of the current is called no-load current. The no-load current consists of a magnetizing current (which generates magnetic flux) and an iron loss current (which is caused by core loss). For a 50Hz power transformer, the no-load current is basically equal to the magnetizing current.

The working principle of the transformer is as follows:Satons transformers mainly apply the principle of electromagnetic induction to work. Specifically:

When the primary side of the transformer applies the alternating voltage U1, and the current flowing through the primary winding is i1, the current will produce alternating magnetic flux in the iron core, so that the primary winding and the secondary winding have electromagnetic contact, according to the principle of electromagnetic induction, the alternating magnetic flux will induce electromotive force through these two windings.

Its size is proportional to the number of winding turns and the maximum value of the main magnetic flux, the voltage on the side with more winding turns is high, and the voltage on the side with fewer winding turns is low, when the secondary side of the transformer is open, that is, when the transformer is no-load, the voltage at the primary and secondary ends is proportional to the number of turns of the primary and secondary windings, that is, u1 u2=n1 n2, but the primary and secondary frequency beams are consistent, so as to achieve the change of voltage.

Technical parametersThere are corresponding technical requirements for different types of transformers, which can be expressed by corresponding technical parameters. For example, the main technical parameters of power transformer are: rated power, rated voltage and voltage ratio, rated frequency, working temperature grade, rubber dust temperature rise, voltage regulation, insulation performance and moisture-proof performance.

The main technical parameters for general low-frequency transformers are: transformer ratio, frequency characteristics, nonlinear distortion, magnetic shielding and electrostatic shielding, efficiency, etc.

The above content refers to: Encyclopedia - Transformer Principle.

The transformer is composed of an iron core (or magnetic core) and a coil, the coil has two or more windings, of which the winding connected to the power supply is called the primary coil, and the rest of the windings are called secondary coils. It can transform AC voltage, current, and impedance. The simplest core transformer consists of a core made of soft magnetic material and two coils with different turns on the core, as shown in the figure.

The function of the core is to strengthen the magnetic coupling between the two coils. In order to reduce eddy currents and hysteresis losses in the iron, the core is made of painted silicon steel sheets. There is no electrical connection between the two coils, and the coils are wound by insulated copper wire (or aluminum wire). One coil connected to AC power is called the primary coil (or primary coil), and the other coil is connected to the electrical appliance called the secondary coil (or secondary coil).

The actual transformer is very complex, and there are inevitably copper loss (coil resistance heating), iron loss (core heating), and magnetic flux leakage (magnetic induction wire closed by air), etc., so in order to simplify the discussion, we will only introduce the ideal transformer. The conditions for the establishment of an ideal transformer are: ignoring the leakage flux, ignoring the resistance of the primary and secondary coils, ignoring the loss of the core, and ignoring the no-load current (the current in the primary coil coil of the secondary coil is open).

For example, a power transformer is close to an ideal transformer when it is running at full load (the output power of the secondary coil is rated at power).

A transformer is a stationary electrical appliance made using the principle of electromagnetic induction. When the original coil of the transformer is connected to the AC power supply, the alternating magnetic flux is generated in the core, and the alternating magnetic flux is universally expressed. The primary and secondary coils are the same, and are also simple harmonic functions, and the table is = msin t.

According to Faraday's law of electromagnetic induction, the induced electromotive force in the primary and secondary coils is e1=-n1d dt and e2=-n2d dt. where n1 and n2 are the turns of the primary and secondary coils. As can be seen from the figure, u1=-e1, u2=e2 (the physical quantity of the original coil is represented by the lower corner mark 1, and the physical quantity of the secondary coil is represented by the lower corner mark 2), and its complex effective values are u1=-e1=jn1, u2=e2=-jn2, so that k=n1 n2, which is called the transformation ratio of the transformer.

From the above formula, u1 u2=-n1 n2=-k, that is, the ratio of the effective value of the voltage of the primary and secondary coils of the transformer is equal to the ratio of its turns and the bit difference between the voltages of the primary and secondary coils is .

And then it is obtained: u1 u2=n1 n2

In the case that the no-load current is negligible, there is i1 i2=-n2 n1, that is, the magnitude of the effective value of the primary and secondary coil currents is inversely proportional to its number of turns, and the phase difference.

And then it can be obtained. i1/ i2=n2/n1

The power of the primary and secondary coils of the ideal transformer is equal p1=p2. It shows that the ideal transformer itself has no power loss. The actual transformer total present loss has an efficiency of =p2 p1. The efficiency of power transformers is very high, up to more than 90%.

The basic principle of a transformer is the principle of electromagnetic induction.

A transformer is a type of electrical device that converts the voltage of alternating current into alternating current of different sizes, or the speaker converts the voltage of direct current into direct current of different sizes. The operating principle of the transformer is based on the principle of electromagnetic induction and Faraday's law of electromagnetic induction. A transformer consists of a coil and two cores.

Among them, one coil is called the primary coil and the other coil is called the secondary coil. Both the primary and secondary coils are wound with wires, and the number of turns of these wires determines the magnitude of the current.

When an electric current is passed through the primary coil, a magnetic field is created in the core. This magnetic field passes through the secondary coil and creates a magnetic field in the secondary coil in the opposite direction of the original magnetic field. Due to the law of conservation of magnetic flux, the strength of the magnetic field in the secondary coil is always equal to the strength of the magnetic field in the primary coil.

Lead old. <>Faraday's law of electromagnetic induction

According to Faraday's law of electromagnetic induction, when the magnetic field changes, an induced electromotive force is created in the conductor. This induced electromotive force causes the current** to flow in the circle. Therefore, when the current in the primary coil changes, a changing magnetic field is created in the core, resulting in an induced electromotive force in the secondary coil.

This induced electromotive force is in the opposite direction to the direction of the original magnetic field and is equal to the rate of change of the original magnetic field.

According to Ohm's law, the magnitude of the current is directly proportional to the voltage and inversely proportional to the resistance. Therefore, when a transformer transforms the voltage from one end to another, the magnitude of the current must be kept constant. To achieve this, transformers often employ multiple windings to increase the magnitude of the current.

In addition, transformers can be made of special materials to reduce magnetic flux losses and eddy current losses, thereby increasing efficiency.

The above content reference: Encyclopedia - Transformer.

1."Is the induced EMF of the primary coil due to self-inductance or the secondary coil"? Both.

If the transformer is unloaded, then there is no current in the secondary coil, it does not produce a magnetic field, it does not have an effect on the primary coil, therefore, "the induced electromotive force of the original coil is caused by self-inductance". The main magnetic flux is generated by i0w1.

If there is a load in the secondary connection, and there is a current in the secondary connection, it will also generate a magnetic field, and it will generate a mutual inductance potential to the primary coil. At this time, there are two kinds of induced potentials: self-inductance and mutual inductance. Since the supply voltage is unchanged, the main magnetic flux is also basically unchanged, which is generated by i1w1+i2w2=i0w1.

2."What does terminal voltage mean"? The primary terminal voltage is the applied supply voltage.

It is equal to the sum of the vectors of the primary induced potential and the primary internal resistance voltage drop. In an ideal transformer, the internal resistance is zero, which is equal to the induced potential. The secondary terminal voltage is the vector difference between its induced potential and the internal resistance voltage drop, ideally, its induced potential.

Note that the voltage and current here are alternating, not DC, and of course the induced potential is also alternating.

3."Why does the output power determine the input"? In terms of energy conservation, the more output, the more input.

The output is the need, and the input is the supply. Of course, the output determines the input. If you turn it over, if there is no output (such as no load) or a small load, there is still an input or a large input, and the input energy goes to **?

It's like tap water, the faucet doesn't turn on, there is no output, will there be an input? Does the water in the pipes flow continuously into the tap? If the human body continues to not excrete, will it continue to eat and drink?

Don't you die? When it comes to the transformer, the secondary output and the current are generated, and the magnetic field it generates will cancel out the primary magnetic field, and the primary current will increase, and the vector synthesis of the two magnetic fields (actually subtracted) will keep the main magnetic flux constant.

Well, that's all.

When the primary side of the transformer applies the alternating voltage U1, and the current flowing through the primary winding is i1, the current will produce alternating magnetic flux in the iron core, so that the primary winding and the secondary winding have electromagnetic contact, according to the principle of electromagnetic induction, the alternating magnetic flux will induce electromotive force through these two windings, and its magnitude is proportional to the maximum value of the winding turns and the main magnetic flux, the voltage on the side with more winding turns is high, and the voltage on the side with fewer winding turns is low, when the secondary side of the transformer is open, that is, when the transformer is no-load, The voltage of the primary and secondary terminals is proportional to the number of turns of the primary and secondary windings, and the transformer plays the purpose of transforming the voltage.

When the secondary side of the transformer is connected to the load, under the action of electromotive force E2, there will be a secondary current through, and the electromotive force generated by the current will also act on the same iron core to play the role of reverse demagnetization, but because the main magnetic flux depends on the power supply voltage, and U1 basically remains unchanged, the primary winding current will automatically increase a component to produce the magnetokinetic potential F1 to offset the magnetokinetic potential F2 generated by the secondary winding current, under the action of the primary and secondary winding currents L1 and L2, The total magnetokinetic potential acting on the iron core (excluding the no-load current i0), f1 + f2 = 0, since f1 = i1n1, f2 = i2n2, so i1n1 + i2n2 = 0, it can be seen from the equation that i1 and i2 are in phase, so.

i1/i2=n2/n1=1/k

It can be seen from the formula that the primary and secondary current ratio and the primary and secondary voltage ratio are the reciprocal of each other, and the power of the primary and secondary windings of the transformer is basically unchanged, (because the loss of the transformer itself is relatively small compared with its transmission power), the size of the secondary winding current i2 depends on the needs of the load, so the size of the primary winding current i1 also depends on the needs of the load, and the transformer plays the role of power transfer.