What are the conditions under which the inverter circuit occurs

How it works. Bridge inverter circuit.

The switching state is determined by the voltage signal applied to its control pole, and direct current is added to the PN terminal of the bridge circuit.

Press UD, A and B are terminated to the load. When t1 and t4 are open and t2 and t3 are closed, u0=ud; Conversely, when t1 and t4 are closed and t2 and t3 are open, u0 = -ud. Therefore, when each arm in the bridge turns on and off at a frequency f (determined by the repetition rate of the control pole voltage signal), the output voltage U0 will become an alternating square wave.

Get: UO=4UD (sinwt+1 3 sin3wt+1 5 sin5wt+..As can be seen from the formula, the frequency of the control signal f can determine the frequency of the output terminal, and changing the DC power supply voltage UD can change the fundamental amplitude, so as to achieve the purpose of inversion.

Inverter circuits. The inverter circuit is with the rectifier circuit.

rectifier) to turn direct current into alternating current.

It is called inverter. Inverter circuits can be used to form a variety of AC power sources and are widely used in industry.

Brief introduction. The inverter circuit corresponds to the rectifier circuit, and the conversion of direct current into alternating current is called inverter. When the AC side is connected to the power grid, that is, when the AC side is connected to the power supply, it is called an active inverter; When the AC side is directly linked to the load, it is called passive inverter.

Inverter circuits are used in a wide range of applications. Among the various power sources available, accumulators, dry batteries.

Solar cells, for example, are DC power sources, and when these sources are needed to supply power to AC loads, inverter circuits are required. In addition, AC motor speed control with frequency converter, uninterruptible power supply.

Power electronics such as induction heating power supplies are widely used, and the core part of their circuits is inverter circuits. Its basic function is to convert the DC power output of the intermediate DC circuit into an AC power supply with arbitrary adjustable frequency and voltage under the control of the control circuit.

A conversion circuit that converts direct current energy into alternating current energy. It can be used to form a variety of AC power sources and is widely used in industry. The most common AC source in production is the public grid that is powered by power plants (China uses RMS for line voltage.

It is 380V, and the frequency is 50Hz power supply system). Supplying power to AC loads from the public grid is the most common way to supply electricity. However, with the development of production, a considerable number of electrical equipment has special requirements for power quality and parameters, so that it is difficult to directly supply power from the public grid.

In order to meet these requirements, there have been electric motor generator sets and ion device inverter circuits in history. However, due to their technical and economic indicators, they are inferior to those used in power electronic devices (such as thyristors.

etc.), which has been or is being replaced by the latter.

Inverter Circuits Encyclopedia.

The conditions for active inverter are:

1. There is a direct current potential that can make the electrical energy flow backwards, and the polarity of the electric potential isThyristorsThe unidirectional conduction direction of the components is consistent, and the magnitude of the electric potential is slightly greater than the average DC voltage of the converter circuit;

2. The DC side of the converter circuit should be able to generate a negative DC average voltage.

In order to achieve active inverter, the two conditions must be met at the same time.

If the circuit will be inverted.

The AC side is connected to the AC power.

On the Internet, converting direct current into alternating current at the same frequency and sending it back to the power grid is called active inverter.

How active inverters work:

Let the motor run in the motor state, and the back EMF e is above ( ) and down ( ) At this time, the thyristor converter circuit must work in the rectification state, so that the output DC average voltage ud 0, and also up ( ) and down ( ) to overcome the effect of the back EMF e, and the output DC average current id is supplied to the armature winding.

At this time, the thyristor controls the angle 0 2, and adjusts so that ud e. In this case, id=(ud-e) rd, generally the id is very small, and the limit id is not too large, and ud e must be controlled. At this time, the electrical energy flows from the AC grid to the DC motor through the converter circuit.

Side. From the waveform diagram, the thyristor works in the range of AC voltage U2 0 most of the time in the rectified state. When u2 0, due to the reactor.

The thyristor is still subjected to the positive anode voltage and turned on.

Active inverter circuits typically convert DC power to 50Hz (or 60Hz) of AC power and feed it into the public grid.

When the AC side of the converter is connected to the power grid, the DC power is converted into AC power of the same frequency and fed back to the power grid. When the AC side of the converter is connected to the load, the converter directly supplies alternating current with variable frequency to the load such as the motor.

The topology of active inverter is exactly the same as that of rectification, except that when the trigger angle is greater than 90 degrees, the power direction of the rectifier circuit changes, which is equivalent to realizing the inverter function. Therefore, the AC side of the active inverter must need a power supply.

(1) The DC side must be connected to the DC power supply E in the same direction as the DC current ID, and its value must be slightly greater than the average output voltage of the inverter UD in order to provide inverter energy. (2) The inverter must work in the <90o(>90o) area to make the UD<0 in order to convert the DC power into AC power and return it to the grid.

Power Electronics Technology

- Su Yugang. Conditions for the realization of active inverter:

1) External conditions: there must be a DC power supply, and its deformity must be consistent with the thyristor in the same direction, and its value should be slightly greater than the average voltage on the DC side of the converter.

2) Internal conditions: The control angle of the thyristor is required to be > 90 degrees, so that UD is supported.

3) Sufficient conditions: There must be a large enough inductance in the circuit tributary circuit to ensure that the active inverter is carried out continuously.

Back EMF is present; The trigger angle a > 90 degrees.

Voltage-type inverter circuit refers to an inverter circuit that is powered by a voltage-type DC power supply. Its DC side is a voltage source, or it is connected in parallel with a large capacitor, which is equivalent to a voltage source, and the DC side voltage is basically non-pulsating, and the DC loop presents low impedance. Voltage-type inverter circuits are mainly used in various DC hidden sources.

Characteristics of voltage type inverter circuit.

1) The DC side is a voltage source or a large capacitor in parallel, and the voltage on the DC side is basically non-pulsating;

2) The output voltage is a rectangular wave, and the output current varies according to the load impedance;

3) Reactive power should be provided when the resistive load is loaded. In order to provide a channel for the reactive power fed back from the AC side to the DC side, feedback diodes are connected in parallel at each arm of the inverter bridge.

Types of voltage-type inverter circuits.

1. Single-phase voltage inverter circuit.

1) Single-phase half-bridge voltage inverter circuit.

Advantages: simple, less use of components.

Disadvantages: AC voltage amplitude UD 2, DC side needs two capacitors in series, to control the stove to guess the voltage balance between the two.

2) Single-phase full-bridge voltage inverter circuit, which is a combination of two half-bridge circuits, is the most widely used in single-phase inverter circuits.

3) Inverter circuit with center tap transformer.

2. Three-phase voltage inverter circuit.

Three single-phase inverter circuits can be combined into a three-phase inverter circuit, and the most widely used is the three-phase bridge inverter circuit.

To put it simply, the parallel capacitor is a voltage type, and the string inductor is a current type.

To put it simply, rectification is to turn alternating current into direct current. Inverter is the conversion of direct current into alternating current.

With the continuous development of electrical equipment, there are many different requirements for AC power supply performance parameters of electrical equipment, which are called a variety of inverter circuits, which can be roughly classified in the following ways:

According to the direction of the output power, it can be divided into active inverter circuit and passive inverter circuit. The electrical energy exported by the former is not returned to the public AC grid, and the electrical energy exported by the latter is directly transmitted to the electrical equipment.

According to the nature of DC power supply, it can be divided into voltage type inverter circuit powered by voltage type DC power supply and current type inverter circuit powered by current type DC power supply.

According to the components of the main circuit, it can be divided into: a fully controlled inverter circuit composed of a fully controlled device with self-shutdown ability; A semi-controlled inverter circuit consisting of a semi-controlled device with independent discontinuous capability (such as an ordinary thyristor). Semi-controlled inverter circuits must utilize a commutation voltage to shut down the exiting conductive device.

If the commutation voltage is taken from the inverter load side, it is called a load commutation inverter circuit. This circuit is only suitable for capacitive loads; For non-capacitive loads, the commutation voltage must be generated by a special commutation circuit, called a self-commutating inverter circuit.

What is Inverter?

Convert DC to AC. Relative to rectification.

What are the two forms of inversion?

Active inverter, passive inverter.

What are the conditions under which inverters arise?

The DC potential is greater than the AC voltage.

1. What conditions must be met for the inverter circuit to carry out the inverter work? Can a single-phase bridge semi-controlled rectifier circuit achieve active inverter? Why?

There are two conditions: 1. There should be an electromotive force on the DC side, and its polarity must be consistent with the conduction direction of the thyristor, and its value should be greater than the average voltage on the DC side of the converter circuit. 2. The control angle of the thyristor is required to be greater than PI 2, so that UD is negative.

Single-phase bridged half-controlled rectifier circuits should be able to achieve active inverter.

3. What is commutation? What are the types of commutation? What are the characteristics of each?

Commutation is the process of changing electricity from one branch to another.

There are 4 types of commutation.

Device commutation, which uses the self-shut-off capability of the fully controlled device for commutation. This commutation is used in fully controlled devices.

Grid commutation, the grid provides the converter voltage, as long as the negative grid voltage is added to the device to be shut down.

Load commutation, the commutation voltage is provided by the load, and when the load is a capacitive load, that is, the load current is ahead of the load voltage, the load commutation can be realized.

Forced commutation, setting up an additional commutation circuit, and applying a reverse voltage to the thyristor to be turned off is called forced commutation. This is usually achieved using the energy on an additional capacitor, also known as capacitor commutation.

4. What is the role of the feedback diode in the voltage inverter circuit? Why is there no feedback diode in a current inverter circuit? What is the energy storage element in the intermediate DC link of the current inverter?

It plays a freewheeling role. The current type uses a freewheeling device, so a reverse diode is not required. Inductance.

5. Describe the commutation sequence of 1800 conductive voltage inverter circuit and the conductive pipe number of each 600 interval.

There are textbooks. It should be 180 degrees and 60 degrees, right?

6. In the single-phase bridge current type parallel resonant inverter circuit using thyristor, the commutation mode of the thyristor is (c).

A Device commutation B Grid commutation C Load commutation D Pulse commutation.

7. Current type inverter, the voltage waveform of the AC side is (A).

a.By changing the switching frequency of the two sets of switches, the output AC frequency can be changed.

b.If you change the AC frequency of the input finger rock out of the coming cavity, you can change the two sets of switching frequencies.

Correct Answer: a