Why is a voltage transformer a step down transformer, and why is a current transformer a step up tra

This is due to the use of these two types of transformers. No matter what kind of transformer it is, it is in line with the various laws of the transformer, but the emphasis is different. For example, the voltage transformer is mainly born to convert the voltage to facilitate the instrument to measure the voltage of the line, and the input range of the instrument for measuring the voltage is generally 0 100V (referring to the use of most industrial instructions), and the maximum will not exceed 1000V, and in real production and life, for the long-distance transmission of electric energy, the voltage level has to be increased to reduce the loss of long-distance transmission, 500kV transmission line, etc., which is far from the input range of the instrument for measuring voltage, and the requirements of the safety party. It is necessary to use a step-down transformer to measure the voltage of the line under various working conditions, so the voltage transformer with a small capacity of step-down voltage transformer was born, and the working range was roughly determined.

The current transformer is similar to the voltage transformer, in order to work needs, it considers the relationship of current, and the relationship of voltage is only a by-product of the law of transformer solidity, which cannot be discarded, just as the voltage transformer is changing the voltage at the same time, and it is also changing the current.

The coil is inversely proportional to the primary and secondary currents and the transformer is proportional to the voltage.

Compared with the primary coil and the secondary coil, the voltage induction is more primary, the secondary is less, and the current induction is the opposite, the form is different, the principle is almost the same, mainly depends on the principle

The voltage transformer is generally higher than 100V, and a step-down transformer is required.

The current transformer is used to reduce the large current to 5A current, and the ratio of the number of turns of the transformer winding is inversely proportional to the current, so the voltage is boosted.

Categories: Education Science >> Science & Technology >> Engineering Technology Science Problem Description:

It seems that the structure of the two is quite similar, and I can't see any difference.

Analysis: The principle of current transformer and transformer is almost the same, and the structure is basically the same, both are two windings: one has more turns and a thin wire diameter, and the other has a few turns and a thick wire diameter.

If the winding with a large number of turns and a thin wire diameter is connected in parallel with the measured circuit as a primary winding, and the winding with a small number of turns and a thick wire diameter is connected to a measuring instrument (voltmeter), then the transformer is a voltage transformer. The voltage transformer is actually a step-down transformer that works in the no-load state (because the voltmeter is a high-resistance meter and the current is very small, it is no-load. And because the number of turns of the primary winding is large and the number of turns of the secondary winding is small, it is a step-down).

If the winding with a small number of turns and a thick wire diameter is connected in series with the measured circuit as a primary winding, and the winding with a large number of turns and a thin wire diameter is connected to a measuring instrument (ammeter), then the transformer is a current transformer. The current transformer is actually a step-up transformer that works in a short-circuit state (because the ammeter is a low-resistance meter and the current is very large, it is equivalent to a short circuit. And because the number of turns of the primary winding is small and the number of turns of the secondary winding is large, it is a boost, and the reason why the secondary winding voltage of the actual current transformer is not boosted is because it works in a short-circuit state).

When the current transformer is working, the secondary winding must not be opened, otherwise it will induce high voltage and endanger the safety of equipment or personnel, and due to the loss of the demagnetizing magnetic potential of the secondary winding, the core will be seriously saturated and the accuracy of measurement will be lost.

What is the transformer ratio of a transformer What is the converter ratio of a current transformer?

What is the transformer ratio of the transformer What is the transformer ratio of the current transformer? Hello dear, the ratio of the rated line voltage on the primary side of the transformer to the rated line voltage on the secondary side is called the transformer voltage conversion ratio. The ratio of the primary rated current to the secondary rated current of the residual current transformer is called the conversion ratio of the current transformer.

1. Different definitions.

1. Transformer: transformer is a device that converts AC voltage, current and impedance, when there is AC current in the primary coil, the iron core (or core) will produce AC magnetism, so that the voltage (or current) is induced in the secondary coil, which is used to change the voltage level and the load is larger.

2. Transformer : Transformer is a kind of voltage conversion device. It converts the high voltage to the low voltage so that the change in the high voltage value is reflected with the low voltage value. Therefore, voltage transformers can be used to measure voltages directly with ordinary electrical instruments.

Second, the capacity is different.

1. The capacity of the transformer is from small to large, from tens of volt-ampere to tens of megavolt-ampere;

2. The capacity of the voltage transformer is very small, usually only tens to hundreds of volt ampere;

Third, the principle is different.

1. Transformer : The structure of the current transformer is relatively simple, which is composed of primary winding, secondary winding, core, frame, shell, terminal block, etc., which are insulated from each other.

2. Transformer: The transformer is a static electrical appliance made by 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 differences between voltage transformers and transformers are as follows:

Different uses: transformers are mainly used for the conversion and transmission of electrical energy in the power system, and are usually used to change high voltage into low voltage. Voltage transformers, on the other hand, are mainly used in electrical measurements to step down a high-voltage signal into a low-voltage signal suitable for measurement.

The working principle is different: the working principle of the transformer is based on the principle of mutual inductance transformation. Through the mutual inductance of the two coils, the voltage of the input coarse shed can be converted into the output voltage.

The voltage transformer also works according to the principle of mutual inductance conversion, the difference is that it has only one secondary coil, that is, the coil used to measure the output signal, and there is no main coil to input voltage.

Different wiring: Transformers can be connected to the circuit in a variety of ways, such as "star connection" and "triangle connection", so that different voltage variations can be realized. The secondary winding of the voltage transformer is usually directly connected to the measuring instrument, and the output signal is processed through the internal circuit of the measuring device.

The rated parameters are different: the rated voltage of the transformer is usually higher than that of the voltage transformer. For example, in a power system, transformers may have voltage ratings of several thousand volts or more, while voltage transformers are generally rated at several hundred volts.

Overall, while voltage transformers and transformers work similarly, they are not the same in terms of use cases and design purposes.

The working principle of transformer and current transformer is the same, the difference is that the structure and use are noisy, the transformer is used for the rise and fall of the pulse voltage change, and the current transformer is used for metering. The main differences are as follows:

The current transformer is strictly forbidden to open the secondary side, because this liquid sock will cause the excitation current of the primary current is all the core, so that it will be saturated and induce high voltage on the secondary side, and the insulation breakdown accident will occur, while the transformer has no such limitation.

The impedance of the load connected to the secondary side of the current transformer is very small, which is approximate to short circuit, and the secondary side of the transformer is not allowed to short circuit.

The design value of the magnetic flux density of the core of the current transformer is low, only; The magnetic flux density of the transformer core, cold-rolled silicon steel sheet, hot-rolled silicon steel sheet.

The secondary current of the current transformer varies with the magnitude of the primary current, while the transformer is reversed, and the magnitude of the primary current is determined by the magnitude of the secondary (i.e. load) current.

Difference: The voltage transformer transmits the rotten state signal as an AC signal through the principle of electromagnetic induction, and the voltage converter outputs a DC current signal or voltage signal through the principle of electromagnetic induction and the rectifier circuit.

Introduction: Voltage transformer (TV) is a sensor that isolates high voltage and is used by relay protection, automatic devices and measuring instruments to obtain secondary voltage information. It is a special type of converter.

The converter transforms the information sent by the source for a certain purpose. Matrix converter embedder is a new type of AC power converter. Compared with conventional converters, it has the following advantages:

There is no need for intermediate DC energy storage; Able to operate in four quadrants; It has excellent input current waveform and output voltage waveform; Freely controllable power factor. Matrix converters have become one of the hot spots in power electronics technology research and have a wide range of application prospects.

The higher accuracy is used as a meter, and the lower accuracy is used as an instrument to measure relay protection.

Some transformers have integrated bushing current transformer (CT) inside the bushing, in order to facilitate transformer protection, if your high, medium and low side switches are equipped with current transformers, you can make a special statement when ordering the transformer, requiring no bushing CT, which can also save a lot of money;

If the transformer itself has a bushing CT, most users choose to use the CT with the three-side switch, if so, then the sleeve CT attached to the transformer bushing can be short-sealed.

The main transformer is not only connected to the bus as an interval, but also an independent component, and its protection is different from that of ordinary lines.

The built-in high-side current transformer is for the need of protection.

The high-voltage side switch of the main transformer also has a current transformer, and its winding is generally provided for bus protection and main transformer backup protection, but cannot be used for the differential protection of the main transformer; The casing CT of the main transformer body is provided for differential protection, main transformer measurement and metrology.

Because there is a range between the main transformer body and the circuit breaker, if it is connected to the CT circuit breaker on the high voltage side, the protection range is expanded.

The load connected in series by the secondary circuit of the current transformer is the current coil of the ammeter and the relay, and the impedance is very small, so the normal operation of the current transformer is equivalent to the transformer of the secondary short circuit.

The voltage transformer is a step-down transformer that drops the primary high voltage of the system into a secondary low voltage for measurement protection.

The function of the current transformer is to raise or drop the current.

The role of voltage transformer is to boost and buck voltage.

They have a very small capacity and can't be used as a transformer at all.

Current transformers and transformers are different in principle and are not comparable.

A voltage transformer is equivalent to a mini-capacity single-phase transformer.

1. To be precise, the capacity of the transformer refers to the rated power, that is, the apparent power, which is the product of the rated voltage and the rated current, and the unit should be VA (volt-ampere), but it is customary for people to say that it is power, and the unit is said to be W (watts). Actually, w is the unit of active power. The apparent power is only the product of voltage and current, and the active power = the product of the apparent power and the power factor.

There is a transformer that is labeled 12V 2W, and its capacity is 2W (preferably 2VA).

Generally, it does not burn out, it is an overload state.

2) When the output current decreases, the output voltage will increase, but it is different from your understanding, the voltage increase is very small, and the reason is the internal resistance of the transformer. If it is analyzed according to the ideal transformer, the voltage does not increase. You seem to be confusing the "power" (actually the capacity) of the transformer with the actual output power, which is variable (usually less than the rated power), like a person can take 50 kg of an object, but he can take 3 kg without much effort.

When the output current decreases, the output power decreases, and the voltage remains the same.

3. That's right.

4. For the current transformer, its output can ideally be the current source (within the capacity), and the load voltage will change.

5. If the line voltage remains unchanged, the output voltage of the voltage transformer will remain unchanged, which can ideally be the voltage source (within the capacity), and the load will change the current. (with 4 pairs).

Current transformer with MA input (What is the conversion ratio?) Its output is a constant current, the output voltage changes with the change of load, the voltage is 0 when the short circuit is not allowed.

7. Its output is a current source, and the current will not change when the output is constant, but the load impedance is very small, and the voltage is not high.

8. Inside the baton is a voltage doubling circuit (relying on capacitor energy storage), as long as it touches the human body, it will be discharged quickly, and the voltage will drop very low immediately. It's a bit like a camera's flash doesn't shine continuously.

10, same as 8.

1.Strictly speaking, the success rate of transformer labeling is wrong, but people have always been so wrong, that's it. The capacity of the transformer is also not equal to the product of the voltage of the transformer and the load current, but is equal to the product of the rated voltage of the transformer and the rated current.

The rated voltage is the winding voltage of the transformer as you understand it, and the rated current can be understood as the maximum current that the transformer can provide, not necessarily the load current.

2.Any power supply has capacity, such as the baton you said, first of all, the voltage is not tens of thousands of volts, generally only around 8000 volts. Secondly, its capacity is very small, that is, the rated current is small, the equivalent internal resistance is very large, once the human body is completely contacted, due to the use of a certain current, its output voltage is immediately very low, naturally can not kill people.

So remember, if you encounter a police officer who uses that thing for you in the future, and you can't run, you will grab it, but it will not be so uncomfortable, hehe.

The first question: the capacity you are talking about is the power. The answer is 2w

The second question: "If the current exceeds this value, will the transformer be burned out?" You can try terminating with a transformer output for 1-2 seconds. It can be seen that the transformer is not broken, but it will break after a long time, which proves that it is related to time.