What do I need to change the voltage frequency?

There are two kinds of frequency conversion technology: AC-AC frequency conversion and AC-DC-AC frequency conversion, and the first method is not very mature and not well understood.

AC-DC-AC frequency conversion should first convert the AC used into DC through the rectifier circuit, the simple process is very complicated, the DC intermediate circuit should smooth the output of the rectifier circuit to make the DC more stable, and then the inverter circuit will reverse the DC into AC, this process is more complicated, in this process to make a new wave, artificially turn the DC into AC, so that the frequency can be controlled.

Generally, the standard frequency of mains power is 50 Hz seconds (5%), which is determined by the speed of the generator, and its frequency is changed if it deviates from its rated speed. The oscillation frequency of general inverters, high-frequency circuit generators and electronic transformers used in electrical appliances is composed of resistor-capacitive components, and once the resistor-capacitance elements are changed, the frequency of their output voltage can be changed.

In the power system, it is by changing the steam turbine valve to change the air intake, or changing the size of the water turbine water gate to change the water intake, so as to adjust the generator speed, and then change the voltage frequency drop

Change the periodic speed of the generator, that is, the rotor of the generator within the species, the number of weeks of transformation, the faster the rotation, the higher the frequency of electricity.

Today's inverter technology is very mature. There are two kinds of constant power and constant torque, and when constant torque speed regulation is required, it is necessary to change the voltage in proportion to the frequency, and then follow.

Uncle, which subject are you asking?

There is a VCO on top of the high frequency

The low frequency has the generator speed on it.

Change the frequency of the resonant loop.

I think your brother wants to ask about inverter technology! If you want to study, you can read the book! If you want to do design! Read the book first!

For constant torque loads, the general inverter is designed according to the constant value of U f = at this time, the magnetic flux remains basically unchanged, and the motor torque also remains basically unchanged.

Fine-tune the speed down to see if the input power of the inverter can be reduced, and try to maintain the output power of the inverter. That is, whether the best efficiency can be achieved near the operating point. Achieve energy savings.

When the frequency of the inverter decreases, it naturally means that the load becomes smaller, so the current must be smaller. The current is only related to the torque force of the load, and the current fluctuates with the load fluctuation.

The frequency and period of AC voltage are closely related, and changing the frequency will lead to a change in the period, because the frequency and the period are reciprocal to each other.

1.Frequency: Frequency refers to the number of periodic changes in voltage per unit of time. It is usually expressed in hertz (Hz), and 1 Hz indicates a periodic change per second. For example, a voltage of 50 hertz means 50 changes per second.

2.Period: A period is the time it takes for a complete cycle of voltage, usually measured in seconds. The period is the reciprocal of the frequency, i.e., the period = 1 frequency. Take 50 hertz, for example, with a period of 1 50 seconds.

When the frequency of the AC voltage is changed, the period is also changed accordingly. If the frequency is increased, it means that the number of changes per second will increase, so the Zhou family period will become shorter. For example, if you increase the voltage frequency from 50 Hz to 60 Hz, the number of changes per second increases, so the period decreases.

Conversely, if the frequency decreases, the period increases accordingly.

This relationship is determined by the design and operation regulations of the power system. In different countries and regions, the standard frequency of AC voltage is usually 50 Hz or 60 Hz. The setting of these frequencies is related to factors such as energy transmission, equipment design, and the stability of the power supply network.

In short, changing the frequency of the AC voltage will lead to a change in the period, and the frequency and the period are reciprocal to each other, and as the frequency increases, the period decreases, and vice versa.

1. Comparison between frequency regulation and voltage regulation.

Frequency adjustment is mainly achieved by adjusting the active power, and voltage adjustment is mainly achieved by reactive power.

of the regulation.

There are big differences between the two adjustments, which are mainly reflected in the following aspects:

1) The frequency of the whole system is the same, and adjusting the active power anywhere in the system can cause frequency changes.

However, the voltage can vary from place to place in the system, and the reactive power can be adjusted locally, which generally only affects the voltage in the nearby area.

This is the difference between the so-called uniformity (frequency) and locality (voltage).

2) From the perspective of the allowable deviation range, the frequency deviation is stricter than the voltage deviation.

3) Frequency is closely related to the active power of the system, the active power is concentrated in the generator, and adjusting the power of the prime mover is the only means of adjusting the frequency (microgrid of the new energy structure.

except), while the voltage is closely related to the reactive power, which can be dispersed in various substations except for the generators of various power plants.

set other reactive power supplies.

4) Reactive power power supply basically does not consume primary energy.

The investment and operating expenses are lower than the active power.

When considering the configuration and load distribution of active power supply, the economic factor is more prominent than that of reactive power supply.

5) As far as the reactive power balance is concerned, the problems encountered during the day and at night are different, when the reactive power is the largest during the day, the most concerned problem is how to distribute the reactive load to minimize the line loss, and the reactive power load is the smallest in the middle of the night, and the concern is how to absorb the excess reactive power.

Therefore, from a mathematical point of view, the optimization problem of reactive load distribution is more complex than that of active load distribution.

Excerpt from: Liu Tianqi, "Power System Analysis Theory".

Second Edition), Science Press.

Year 2011.

Note: This excerpt is not for commercial use.

The frequency adjustment is mainly through active power regulation, so only the prime mover power can be adjusted.

It has two characteristics: 1. Strict requirements; 2. Uniformity.

The active power has more stringent requirements for small deviations.

The frequency is the same everywhere in the system, which is its unity.

Voltage adjustment is mainly through reactive power regulation, its reactive power supply is widely distributed, can be set in the generator of various power plants, can also be all kinds of substations.

It has three characteristics: 1. Locality; 2. Economy; 3. Complexity.

The voltage varies from place to place in the system, which is its locality.

The reactive power supply basically does not consume primary energy, so its investment and operation cost is lower than that of active power (frequency adjustment), which is its economy.

Balancing reactive power varies from time to time: during the day it is about how to distribute the reactive load to minimize line loss, and at night how to absorb excess reactive power. This is its complexity.

The speed of the motor can be adjusted freely, and the resistive size of the inductance coil can be artificially adjusted in the electronic circuit.

Frequency is a physical quantity that indicates how fast or slow the alternating current changes over time. That is, the number of times the alternating current changes per second is called the frequency, which is represented by the symbol f. It is measured in seconds and is also known as hertz, which is often expressed as "Hz", referred to as weeks or hertz.

For example, the mains is 50 cycles of alternating current, and its frequency is f = 50 cycles. For higher frequencies, kilocycles (kc) and megacycles (mc) can also be used as frequencies.

AC sine wave: 1,000 cycles (kc) = 103 cycles, 1 trillion cycles (mc) = 103 thousand cycles (kc) = 106 cycles.

For example, the frequency of signals emitted by China's first artificial earth satellite is megacycles, that is, it emits alternating signals that change times per second. The angular frequency in the expression of the alternating current sinusoidal current in i=asin( t+ ) is also a physical quantity that reflects the speed of the alternating current with time. The relationship between angular frequency and frequency is =2 f.

The speed of alternating current with time can also be described by the physical quantity of cycle. The time it takes for an alternating current to change once is called a period, which is represented by the symbol t. The unit of the period is seconds. Obviously, the period and frequency are reciprocal to each other, ie.

It can be seen that the faster the alternating current changes with time, the higher its frequency f and the shorter the period t. Conversely, the lower the frequency f, the longer the period t.

The capacitor is charged and discharged twice in one cycle of alternating current. During charging, the charge that enters the capacitor first repels the charge that enters the capacitor later (the same charge repels each other). This is the basic reason why capacitors hinder alternating current.

When the alternating current frequency is changed, another property, the period, will change.

The application with the greatest frequency change is the ability to freely adjust the speed of the motor without changing the motor structure!

In the electronic circuit, the resistive magnitude of the inductor coil and the nature of the magnetic field can be artificially adjusted: such as the industrial intermediate frequency electric furnace, the household induction furnace .........

The main magnetic flux of the motor.

m u (in the above equation, u is the stator voltage, that is, the voltage output by the inverter, f is the frequency, n is the number of turns of the stator winding.)

n is a constant. Obviously, when the frequency changes, if the voltage does not change, then the magnetic flux changes.

The iron core of the motor is nonlinear, and when the magnetic flux changes, whether it is too large (saturated) or too small (weak magnet), it is not good for the motor.

Therefore, when the frequency is changed, the voltage is also changed, and the u f is kept constant, so that the magnetic flux can be maintained.

1. When the power supply frequency of the AC motor decreases, the current will increase rapidly, and the motor will be burned.

2. The function of the inverter is to reduce the frequency of the power supply while limiting the voltage and current of the motor.

3. Power. p=ui

The voltage decreases, the current decreases, and the output power decreases. This is the principle of frequency reduction and power saving of frequency converter.

Because the development principle of the inverter is p=v f, the frequency is proportional to the voltage, so the two will change at the same time, I hope to help you! Deeper can be continued privately! Henan Delta ** business.

The instantaneous value of voltage is equal to the maximum value of voltage, multiplied by sine (2 times frequency multiplied by time plus initial phase.

That's for sure, the curve relationship between voltage and frequency should be set according to the load situation, but the voltage will remain at the rated voltage after exceeding the rated frequency of the motor.

Because the stator phase voltage of the three-phase asynchronous motor is proportional to the product of frequency and magnetic flux, when the frequency is adjusted downward, if the voltage is maintained, the magnetic flux must increase, which will cause the main magnetic circuit to be oversaturated, so that the excitation current will increase sharply and damage the motor.

So, when the frequency is adjusted downward, the voltage is usually adjusted downwards in proportion as well.

However, when adjusting the frequency upward, the voltage cannot be adjusted upwards in order to avoid overvoltage damage to the motor. Therefore, when the motor is overclocked with an inverter, the magnetic flux decreases and the output torque characteristics of the motor shift to the left.

The correspondence between the output frequency of the inverter and the output voltage: the output frequency of the inverter is proportional to the output voltage. p (power) = q (flow rate) h (pressure), flow q is proportional to the primary square of the speed n.

For example, when the output frequency is adjusted from 50Hz to 30Hz, the measured output voltage is 232V. In this case, the output frequency is 60% of the rated frequency, and the output voltage is also 60% of the input voltage.

The correspondence between the output frequency of the inverter and the input current: the output frequency of the inverter is proportional to the cube of the input current.

For example, when the output frequency is adjusted from 50Hz to 30Hz, the rated current of the motor = 200A, then the input power = =.

When it is a constant torque load, when the frequency of the inverter drops from 50Hz to 30Hz, the voltage increases slightly, and the current will rise, but in the end it basically maintains the original current.

When the frequency of the inverter is reduced, if the load size does not change, the current will not change and the voltage will drop.

Ignoring the dynamic process, the voltage and current remain unchanged after stabilization.