Network converter. Pulse network voltage converter. How noise are associated with frequency converter

The use of a pulsed voltage converter allows to reduce the dimensions and the weight of the power supply, which is especially important for portable structures.

Fig. 1. Pulse voltage converter

The converter (Fig. 1) is designed to power from the network 220 in the devices with a current consumption to 3 A at the UI \u003d 9.2 V (to obtain from this voltage 5 or 6 V, any standard diagram of a linear stabilizer can be used).

The proposed converter differs from similar to the simplicity and presence of protection of the power supply from overload over the output circuit in the event of a short circuit.

The electrical circuit of the device consists of an input filter (elements C1, C2, SZ and T1); launch chains (R2, R3, R4, C4, VT1); autogenerator (VT2, VT3, T2, TK, C5); Low voltage rectifier (VD5, VD6, C12, C13). The converter is assembled in a semi-seater.

The input filter of the converter ensures weakening of the interference from the frequency of 15 kHz more than 2 times.

In the starting circuit, the VT1 transistor is used in a reversible breakdown mode, which allows you to form short pulses that are required at the time of inclusion of the circuit to start the operation of the key cascade VT2, VT3 in the autogenerator mode at 30 ... 60 kHz, while the operating frequency, in small The limits can be changed with C5 capacitance.

In the event of a closure in the secondary winding circuit, the TK transformer feedback in the autogenerator is violated and the generation breaks up until the malfunction is removed.

The efficiency of the converter at a load current 2 A is 0.74 (at a current 4 A-0.63).

Resistors of any type can be used in the device, C1 type K73-17 capacitors to 630 V; C2, SZ type K73-9 or K73-17 by 250 V; C4, C5 type K10-7; C6, C7 type K50-35 to 250 V; C8, C9 type K73-9 at 250 V; C10 ... C12 Type K10-17; C13 type K52-1V on 20 V.

The VT1 transistor can be replaced by KT312A, B, B, transistors VT2 and VT3 on KT838A, KT846B.

Throttle T1 is wound on two glued together ring cores sizzy K20x12x6 from Ferrite Mark 2000mm. Winding 1 and 2 contain 45 turns of the wire PEV-2 with a diameter of 0.25 mm. The T2 transformer is made on two glued together ring cores of the K10x6x3 sizes from ferrite 2000mm. Winding 1 contains 60 turns, windings 2 and 3 - 15 turns of the wire PELSHO-0.15 (removal in the winding 2 for the current feedback from the third turn). For the manufacture of TK, a ring core K28x16x9 (2000HM) is applied. Winding 1 is wound with 250 coils with a wire of PEV-2 0.25, winding 2 and 3 - 22 with a wire of the PEV-2 with a diameter of 0.51 mm.

When making transformers before winding the wire, it is necessary to round the sharp edges of the cores and wrap them with lacket. Winding to carry out a turn to a turn with a subsequent insulation of each layer (it is better to use fluoroplastic tape with a thickness of 0.1 mm).

The diodes used VD1 ... VD4 can be replaced with any high-voltage, replacement of VD5 and VD6 diodes, except on CD2998V, not recommended by another type.

The greatest heat dissipation in the diagram occurs on rectaging diodes VD5, VD6, and they must be installed on the radiator. The remaining details of the scheme in the heat sink do not need.

Constructively all the elements of the scheme, except for the S1 switch S1 and Diodes VD5, VD6, are placed on a one-sided printed circuit board with a size of 140x65 mm. The topology of the printed circuit board is shown in Fig. 2.

Before the initial turning on the converter, you must check the winding phases in the VT2 and VT3 base circuits for compliance with the diagram. If the transducer does not immediately start working at the right installation, it will be necessary to change the conclusions of the winding 1 in the T2 transformer.

In conclusion, it should be noted that, using this scheme, other stresses in the secondary circuit can be obtained, for which it is necessary to change proportion to the number of turns in the secondary windings 2 and 3 of the TZ transformer.

Fig. 5.10 a. Topology PCB

Chip 1182EM2 is a representative of high-voltage electronic circuits. The main purpose of use is the direct transformation of the 220 V network voltage transformation into the straightened constant.
Due to the unique technology, the microcircuit is possible for the AC network to 264 V.

Features of application

• Wide range of input voltage from 18 V to 264 V
• Wide input frequency range from 50 to 400 Hz
• Limit output permanent current - 100 mA

The KR1182E2 microcircuit is designed to create compact power sources from the AC network of non-isolated type, for example, for engines of electrodes, auxiliary - for powerful network pulse power supplies, etc. In fig. 1 shows a functional electrical circuit. A typical circuit of the inclusion and temporary diagram of the microcircuit work is presented in Fig. 2.3.

The microcircuit contains 4 high-voltage diodes, key stabilizer, protective stabilizer and output diode. The key stabilizer through an external current-limiting resistor R1 and the input diodes connect an external cumulative capacitor C3 to the AC network until it charges to the voltage determined by the external stabilion with a breakdown voltage of less than 70 V, included between the conclusions 7 and 5 of the chip. If the external stabilion is not installed, then this voltage will be determined by internal protective stabilion and will be 70-90 V. The stabilizer turns off the tank from the network until the next half-wave of the network voltage. In the remaining cycle time, the C3 capacitor feeds the load. The next activation cycle of the stabilizer occurs after the input voltage is transmitted after 0 V when the voltage is reached at its input by about 1.5 per more than on the cumulative condenser. The inclusion frequency of the stabilizer, that is, the capacitor's charge frequency is determined by the inclusion circuit in the input diodes - single-alterogeneous or double-speaker, and corresponds to the frequency or twice frequency of the input voltage. This control principle allows you to apply a chip only when connecting to the AC network and provides the possibility of a normal functioning of the chip when the input voltage changes from 18 to 264 V and the frequency of the input voltage from 48 to 440 Hz. At the input of the circuit, a constant voltage is obtained, having a pulsation with a frequency or twice frequency of input voltage and the magnitude, directly proportional to the load current and inversely proportional capacitance C3.
The output diode is designed to suppress negative voltage emissions when working on an inductive load.

Basic inclusion schemes

A typical circuit of switching on allows you to implement power supplies according to a two-wire diagram for a large range of input voltages and output currents.
The following is a list of external components, a description of their destination and recommended values. For each specific power source, not all of them may be required.
F1 - fuse. Need to protect the chip and load in an emergency. Recommended fuse rating - 500 mA.
R1 - limiting resistor. Limits the current key stabilizer and C3 capacitance current. The peak value of the current UI PEAK / R1 should not exceed 2,5A.
The nominal and power R1 is selected in accordance with the intended scope of application, provided that the maximum charge current is not exceeded. It is advisable to use a resistor with a negative temperature coefficient. Recommended value R1 \u003d 150 Ohm.
C1 - filter capacitor. R1 and C1 form a filter smoothing high-frequency input voltage emissions. It is recommended C1 \u003d 0.05μF.
Mon - protection against overvoltage. It is possible to use a variable voltage variable voltage to 120 V or gas-discharge lamp by 500 V for AC voltage up to 240 V.
C2 - delay condenser. Connecting the power supply to the mains voltage, in the general case, it does not synchronize with it. It is likely to happen at the moment when the input voltage is close to peak voltage or even at higher voltages associated with network emissions.
Since the accumulative capacitor is completely discharged, then a larger will flow through the chip, compared to the established current mode. To increase the reliability of the source and without prejudice to its characteristics, it is advisable to block the inclusion of the stabilizer to the next half-wave, which is guaranteed by connecting the C2 capacitor to 150 PF with an operating voltage 10 to above the output.

C3 - cumulative capacitor. This capacitor is charged twice for the input voltage period, the rest of the time feeds the load. The capacitance of the capacitor is selected in proportional to the desired maximum load current. Increased C3 tank reduces output voltage ripples. For maximum load current, a 44 μF capacitor with an operating voltage is 10 tops above the output.
VD1 - Stabilirt. It sets the level of output voltage. In its absence, an internal protective stabilion works at 70-90 V.

If you need to turn on and off the constant output voltage, without turning off the input network, then it is proposed to connect a mechanical switch, optocoupled or an open collector transistor to the output.

For electroplating junction from the AC network, the separating transformer is possible.
If a total bus for load and network voltage is needed, then it is possible to turn on the scheme in one-alocirode mode.

ATTENTION!!!

Compared to conventional power supplies on transformers, the power source based on chip KR1182EM2 does not have a galvanic junction. When developing the desired design, you should remember the need for appropriate isolation. Any plug-in scheme should be considered as not isolated.

Maximum allowable electrical modes

CJSC "NTC Schemerykhniki and Integral Technologies"

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When the engine is running, unwanted phenomena are often born, which are called "higher harmonics". They negatively affect cable lines and power supply equipment, lead to unstable equipment. It turns out a low-efficient use of energy, rapid aging of isolation, reduced process of transmission and generation.

To solve this problem, it is necessary to comply with electromagnetic compatibility requirements (EMC), the execution of which will ensure the sustainability of technical means to negative impacts. The article made a small excursion to the electrical engineering area associated with filtering input and output signals of the frequency converter (IF) and increasing engine performance.

What is electromagnetic noises?

They arise literally from all metal antennas, collecting and radiating disorientating energy waves. And cell phones, of course, also suggest magnetoelectric waves, so when take-off / landing the aircraft, the stewardles are asked to disable the equipment.

Noise are separated by the type of sources of their occurrence, according to the spectrum and characteristic features. Electric and magnetic fields of different sources due to the presence of switching links are created by the cable line unnecessary potential differences increasing on useful waves.

Arriving in the wires of interference is called anti-phase or syphase. The latter (they are also called asymmetric, longitudinal) are formed between cable and earth, and act on the insulating properties of the cable.

The most common noise sources is inductive equipment (containing coils), such as asynchronous motors (blood pressure), relays, generators, etc. Noise can enter into a "conflict" with some devices, inducing the electrics in their chains, causing malfunction process.

How are noises related to the frequency converter?

Converters for asynchronous engines with a dynamically changing operating mode, having a lot of positive, have a number of disadvantages - their use leads to intensive electromagnetic interference and filing, which are formed in devices associated with them on the network or located near and exposed to radiation. Often, hell is placed remotely from the inverter and connect with it an elongated wire, which creates threatening backgrounds of the exit of the electric motor.

Surely someone had to face pulses from an electric motor encoder on the controller or with the issuance of an error when using long wires - all these problems, one way or another, are associated with electronic technology compatibility.

Frequency transduce filters

To improve the quality of control, the attenuation of the negative effect uses a filtering device, which is an element with a nonlinear function. The frequency range is set, beyond which the reaction begins to weaken. From the point of view of electronics, this term is often used when processing signals. They define the restrictive conditions for current pulses. The main function of the frequency is to generate useful, decrease in unwanted oscillations to the level established in the relevant standards.

There are two types of devices depending on the location of the circuit, referred to as the input and output. "Login" and "Exit" means that the filtering devices are connected to the input and output side of the converter. The difference between them is determined by their use.

Entrances are used to reduce the noise of the power supply cable line. They also affect the devices connected to the same network. Weekends are intended for interference for devices located with an inverter and using the same land.

Purpose of filters for frequency converter

In the process of functioning, the frequency converter is an asynchronous engine, unwanted higher harmonics are created, which, together with the inductance of wires, lead to the weakening of the noise immunity of the system. Due to the generation of radiation, the electronic technology begins to work incorrectly. Actively functioning provide electromagnetic compatibility. Some equipment imposed increased requirements for noise immunity.

3rd phase filters for the frequency allow you to maximize the degree of conduit interference in a wide frequency range. As a result, the electric drive fits well into a single network, where several equipment is involved. EMC filters should be placed on a sufficiently close distance to the power inputs / outputs of the frequency converter, in view of the dependence of the level of interference from the length and method of laying the power cable. In some cases, they are installed.

Filters are required for:

• noise immunity;
• smoothing an amplitude spectrum to get pure electrotes;
• selection of frequency ranges and data recovery.

All models of vector frequency converters are equipped with network filtering. The presence of filtering devices provides the required EMC level to operate the system. The built-in device makes it possible to minimize the enhancers in electronic techniques, and therefore satisfies compatibility requirements.

The absence of the filtering function in the frequency converter often leads to the focusing heating of the supply transformer, impulse changes, distortions of the form of the supply curve, which causes the work failure.

The devices that are absolutely necessary to ensure the stability of the work of complex electronic technology. Between the frequency converter and the power supply, the buffer is mounted to protect the line from higher harmonics. It is able to restrain these waves whose frequency is more than 550 Hz. When stopping a powerful asynchronical system, a voltage jump may occur. At this point, protection is triggered.

It is recommended to establish to suppress high-frequency harmonics and adjust the system coefficient. The importance of the installation is to reduce the losses in the stators of the electric motor, the unwanted heating of the aggregate.

Network chokes possess advantages. The correctly selected inductance of the device allows you to ensure:

• protection of the frequency converter from voltage drops and phase asymmetric
• the speed growth rate of the CW is reduced;
• increases the duration of the "life" of condensers.

You can submit a condenser as a block. Therefore, depending on the method of connecting the condenser, it can act as:

• low-frequency if you connect it parallel to the source;
• high-frequency if you connect consistently with the source.

In practical schemes, a resistor may be required to limit the electronic flow and achieve the correct cut-off of the frequency.

2. Electromagnetic radiation filters (AM)

Do you use a tea strainer during tea cooking? It is used to prevent "unwanted! Elements from entering your system. In electrical circuits there are many similar unwanted phenomena that appear in different frequencies.

The electric drive in the frequency converter and the electric motor is considered to be variable load. These devices and inductance are conducted by the emergence of high-frequency voltage fluctuations and, as a result, electromagnetic radiation of cables, which negatively affects the operation of other devices.

This is an inducer with two (or more) windings in which the current flows in opposite directions. The use of this device consisting of choke and capacitor has a number of advantages. It is more reliable and can be used at the lowest working temperatures. All this allows you to increase the service life of the electric motor. Low inductance and small size are also its key features.

Applied in cases where:

• from the frequency converter to the electric motor stretched cables up to 15 m long;
• there is a chance to damage the insulation of the engine windings due to the pulsating voltage jumps;
• applies old aggregates;
• in systems with frequent braking;
• the aggressiveness of the medium.

At quite high frequencies, the voltage drop is almost equal to zero, and the capacitor behaves like an open chain. FilprPress is made in the form of a voltage divider with a resistor and a condenser. It is essentially used in order to reduce bandwidth, instability and fix the rate of increment of UR.

Speaking with simple words, the usual throttle comes from the word "choking". And still used, because quite accurately describes his destination. Think how the "fist" is compressed around the wire to prevent sharp changes in current.

4. Sinusoidal filters

Variable electrotes is a wave, some combination of sine and cosine. Various sinusoidal waves have different frequencies. If you know what frequencies are present, what you need to transmit or remove, then as a result, you can get a combination of "useful" waves, that is, without noise. It helps to some degree clean the current signal. The sinusoidal filter is a combination of capacitive and inductive elements.

One of the measures to ensure electromagnetic compatibility is the use of a sinusoidal apparatus, it is necessary:

• with a group actuator with one transducer;
• when operating with a minimum switching connections with cables (without a screen) of the electric motor (for example, connecting a loop or suspended energy supply);
• to reduce losses on long cables.

The appointment of the device is to prevent damage to the insulators of the electric motor winding. Due to the almost complete absorption of high pulses, the output voltage takes a sinus form. Its proper installation is an important aspect to reduce the level of interference in the network and, therefore, radiation. This allows the use of a long wire and helps to reduce the noise level. Low inductance also means smaller size and lower price. Devices are designed by the DU / DT filtering method with a difference in a large side of the nominal value of the elements.

5. High-frequency filters of syphase interference

If the distorted voltage sinusoid behaves as a number of harmonic signals added to the main frequency, the filtering circuit allows you to skip only the main frequency, blocking unnecessary higher harmonics. The filtration input apparatus is intended to suppress high-frequency noise.

The devices differ from the above constructed design. The most important way to reduce noise is the compliance with the required grounding rules in the electrical cabinet.

How to choose the right input and output filter EMC

Their distinctive advantages are in a high noise-eyed coefficient. EMCs are used in devices with pulse power sources. It is necessary to adhere to the requirements of the instructions for a specific management scheme of asynchronous engines. There are general principles that determine the correctness of the choice.

It is necessary to note that the selected model must match:

• parameters of the frequency converter and power supply;
• the level of reducing interference to the required limits;
• frequency parameters of electrical circuits and installations;
• features of operating electrical equipment;
• elelectrome model of model in the control system, etc.

The easiest way to improve the quality of the electrical network is to take action at the design stage. The most interesting thing is that with an unreasonable deviation from design solutions, the wine completely falls on the shoulders of electrical installations.

The correct decision on the choice of the type of frequency converter, together with a suitable filter hardware, prevents the occurrence of most problems for the functioning of the power actuator.

Providing good compatibility is obtained with the correct selection of component parameters. Incorrect use of devices can increase the level of interference. In realities, entrance and output filters sometimes negatively affect each other. This, especially, concerns the case when the input device is built into the frequency converter. The selection of the filtering device to a specific converter is carried out by technical parameters and is better at the competent recommendation of the specialist. Professional consultation may bring you a significant benefit, since expensive equipment is in fact a qualitative inexpensive analogue is always selected. Either it does not act in the desired frequency range.

Conclusion

Electromagnetic effect affects equipment mainly at high frequencies. This means that the correct operation of the system will be achieved only when the rules of electrical installation and production and technical requirements are followed, and the requirements for high-frequency equipment are performed (for example, shielding, grounding, filtering).

It is worth noting that measures to increase noise immunity is a set of events. Using only alone filters will not solve the problem. However, this is the most effective way to remove or rather significantly reduce malicious interference for normal electromagnetic compatibility of electronic technology. We must also forget that it is suitable or not a specific model for solving the problem - is determined by "in place" or by experiment and testing.

Impulse sources of secondary power supply were widely distributed in household and industrial equipment. Pulsed power sources produce constant and voltage variables required for the power supply of equipment blocks by key conversion of the straightened network voltage 220 volts and 50 hertz.
The advantage of the UPS compared to the traditional transformer power supply is provided by the replacement of a power transformer operating at a frequency of industrial network 50 hertz, a small-sized pulsed transformer operating at frequencies 16 - 40 kilohertz, as well as the use of pulsed methods for stabilizing secondary voltages instead of compensation. This leads to weight loss and dimensions of the product 2-3 times and increased Efficiency of the source up to 80 - 90% So, additionally saves electrical energy.
The key cascades of the voltage converter are built using one-inclusive and two-stroke schemes.
In the old transistor televisions, due to their specific circuit construction, one-bit UPS were used.
Single UPSs are also used in low-power devices. up to 50 watts. and more.
A visual example is various chargers for powering mobile phones, laptops and many other. They found widespread due to ease of manufacture, small size and high reliability.


The figure shows the charger card from a mobile phone. It converts an alternating voltage of 110 - 220 volts to a constant voltage of 5 volts.

An increase in the power of one-bit UPS turns out to be ineffective due to the growth of the overall dimensions and mass of the pulse transformer (in comparison with the two-stroke scheme) and increased requirements for key transistor (high voltage and current).
Two-stroke UPSs are used for capacities from a few watts to hundred watts , in view of their simplicity and economy.
An example of using a two-stroke converter:

20 watt energy-saving lamps.

Powerful computer power supplies

Single scheme UPS

The dispatching diagram of the UPS is an alternating voltage converter of a network (or constant battery voltage) of one value, in constant (straightened) voltage of another value.
Voltage generator, a frequency of 20 - 100 kilohertz, can be with self-excitation (autogenerator) or with external excitation (optional generator).
In low-power (up to 10 watts) and simple UPS, a self-excited autogeneratorial converter is mainly used.
See the simple scheme of one-stroke, with self-excitation, impulse power supply.


The dispatch diagram of the UPS consists of rectifier (D1 - D4) with a smoothing capacitor C1. In it, the voltage of the network 220 volts is converted into a constant voltage of 310 volts. Then with help generatora pulse voltage (transistor T, transformer Tr), rectangular pulses produced. From the secondary winding, rectangular impulses come on rectifier (D6) with a smoothing capacitor (C5), it turns out a constant voltage.
The voltage conversion itself occurs on a ferrite transformer. The output voltage depends on the ratio of turns in the primary and secondary windings of the transformer.
A significant disadvantage of the one-dimensional converter scheme is a large self-induction voltage, inspected in the primary winding of the transformer, which is 2-4 times higher input power supply voltage. In such schemes, we need transistors that have maximum voltage collector - Emitter equal 700-1000 VOLT.

Apply various ways to reduce voltage emissions on the transistor collector:
- RC chains (C2, R3) parallel to the primary transformer winding and C4 condenser in the secondary winding circuit are turned on.
- When using additional output voltage stabilization devices, such as pulsed modulation (PWM), it is possible to work a one-stroke UPS when the connected load is changed over a wide limits (from p \u003d 0 to Pmax) with a constant output voltage.
Other technical techniques for protecting the key transistor from overvoltage are used.

Pros and disadvantages of the one-stroke scheme of the UPS.

Pros:
- one key transistor in the scheme,
- The scheme is easier than the two-stroke.

Minuses:
- Magnetization of the ferrite core occurs only in one polarity, (passive core demagnetization), as a result of which the magnetic induction of the core is not fully used. Ferrite power core is not fully used. A clearance is needed in a magnetic core.
- with an average current consumption from the network, the current through the transistor is greater than in N-times (depends on the wellness of the pulses) and therefore it is necessary to choose a transistor with a deliberately large maximum current.
- There are large overvoltages on the elements of the scheme, reaching 700 - 1000 volts.
- It is necessary to apply special overstrain protection measures on the elements of the scheme.

Two-stroke scheme UPS

The two-stroke auto bearer diagram of the UPS consists of a rectifier of the input voltage 220 volt, the generator start device, the generator of rectangular pulses and the output voltage rectifier with the filter condenser.
The figure shows the simple most common two-stroke scheme of the autogenerator, the pulse converter - the inverter, the semi-alien circuit.

Compared to a single-acting autogenerator, the two-stroke autogenerator has a more complex scheme.

Added:

- device automatic launch of the pulse generator;
- another key transistor;
- additional transformer TP1, to manage key transistors;
- two capacitor half (C3, C4);
- Two diodes (D5, D8) to protect transistors from breakdown.

The two-stroke diagram of the UPS has several advantages over the one-stroke scheme:

- the ferrite core output transformer TP2 works with active reclamation (the magnetic core is most fully used);
- voltage collector - Emitter UEK on each transistor does not exceed the voltage of the power supply of 310 volts;
- when changing the load current from i \u003d 0 to IMAX, the output voltage varies slightly;
- high voltage emissions in the primary winding are very small, respectively less levels of emitted interference

Despite the increased complexity, the two-stroke scheme, in comparison with the one-stroke, easier to set up and operate.