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Scheme of operation of a chamber-type recuperator. Heat recovery in ventilation systems: operating principle and design options

Scheme of operation of a chamber-type recuperator. Heat recovery in ventilation systems: operating principle and design options

Due to the increase in tariffs for primary energy resources, recovery has become more relevant than ever. In air handling units with recovery, the following types of recuperators are usually used:

  • plate or cross-flow recuperator;
  • rotary recuperator;
  • recuperators with intermediate coolant;
  • Heat pump;
  • chamber type recuperator;
  • recuperator with heat pipes.

Principle of operation

The operating principle of any recuperator in air handling units is as follows. It provides heat exchange (in some models - both cold exchange and moisture exchange) between the supply and exhaust air flows. The heat exchange process can occur continuously - through the walls of the heat exchanger, using freon or an intermediate coolant. Heat exchange can also be periodic, as in a rotary and chamber recuperator. As a result, the exhaust air is cooled, thereby heating the fresh supply air. The cold exchange process in certain models of recuperators takes place during the warm season and makes it possible to reduce energy costs for air conditioning systems due to some cooling of the supply air supplied to the room. Moisture exchange occurs between the flows of exhaust and supply air, allowing you to maintain comfortable humidity in the room all year round, without the use of any additional devices– humidifiers and others.

Plate or cross-flow recuperator.

The heat-conducting plates of the recuperative surface are made of thin metal (material - aluminum, copper, stainless steel) foil or ultra-thin cardboard, plastic, hygroscopic cellulose. The supply and exhaust air flows move through many small channels formed by these heat-conducting plates in a counterflow pattern. Contact and mixing of flows and their contamination are practically excluded. There are no moving parts in the recuperator design. Efficiency rate 50-80%. In a metal foil heat exchanger, due to the difference in air flow temperatures, moisture may condense on the surface of the plates. In the warm season, it must be drained into the building's sewerage system through a specially equipped drainage pipeline. In cold weather, there is a danger of this moisture freezing in the recuperator and causing mechanical damage (defrosting). In addition, the formed ice greatly reduces the efficiency of the recuperator. Therefore, when operating in the cold season, heat exchangers with metal heat-conducting plates require periodic defrosting with a flow of warm exhaust air or the use of an additional water or electric air heater. In this case, supply air is either not supplied at all, or is supplied to the room bypassing the recuperator through an additional valve (bypass). Defrost time averages from 5 to 25 minutes. A heat exchanger with heat-conducting plates made of ultra-thin cardboard and plastic is not subject to freezing, since moisture exchange occurs through these materials, but it has another drawback - it cannot be used for ventilation of rooms with high humidity for the purpose of drying them. The plate heat exchanger can be installed in the supply and exhaust system in both vertical and horizontal positions, depending on the requirements for the size of the ventilation chamber. Plate recuperators are the most common due to their relative simplicity of design and low cost.



Rotary recuperator.

This type is the second most widespread after the lamellar type. Heat from one air stream to another is transferred through a cylindrical hollow drum, called a rotor, rotating between the exhaust and supply sections. The internal volume of the rotor is filled with tightly packed metal foil or wire, which plays the role of a rotating heat transfer surface. The material of the foil or wire is the same as that of the plate recuperator - copper, aluminum or stainless steel. The rotor has a horizontal axis of rotation of the drive shaft, rotated by an electric motor with stepper or inverter control. The engine can be used to control the recovery process. Efficiency rate 75-90%. The efficiency of the recuperator depends on the flow temperatures, their speed and rotor speed. By changing the rotor speed, you can change the operating efficiency. Freezing of moisture in the rotor is excluded, but mixing of flows, their mutual contamination and transfer of odors cannot be completely excluded, since the flows are in direct contact with each other. Mixing up to 3% is possible. Rotary heat exchangers do not require large amounts of electricity and allow you to dry air in rooms with high humidity. The design of rotary recuperators is more complex than plate recuperators, and their cost and operating costs are higher. However, air handling units with rotary heat exchangers are very popular due to their high efficiency.


Recuperators with intermediate coolant.

The coolant is most often water or aqueous solutions of glycols. Such a recuperator consists of two heat exchangers connected by pipelines with a circulation pump and fittings. One of the heat exchangers is placed in a channel with the exhaust air flow and receives heat from it. The heat is transferred through the coolant using a pump and pipes to another heat exchanger located in the supply air channel. The supply air receives this heat and heats up. Mixing of flows in this case is completely excluded, but due to the presence of an intermediate coolant, the efficiency coefficient of this type of recuperator is relatively low and amounts to 45-55%. Efficiency can be influenced using a pump by influencing the speed of the coolant. The main advantage and difference between a recuperator with an intermediate coolant and a recuperator with a heat pipe is that the heat exchangers in the exhaust and supply units can be located at a distance from each other. The installation position for heat exchangers, pumps and pipelines can be either vertical or horizontal.


Heat pump.

Relatively recently, an interesting type of recuperator with an intermediate coolant has appeared - the so-called. thermodynamic recuperator, in which the role of liquid heat exchangers, pipes and pump is played by refrigeration machine operating in heat pump mode. This is a kind of combination of a recuperator and a heat pump. It consists of two refrigerant heat exchangers - an evaporator-air cooler and a condenser, pipelines, a thermostatic valve, a compressor and a 4-way valve. Heat exchangers are located in the supply and exhaust air ducts, a compressor is necessary to ensure circulation of the refrigerant, and the valve switches the refrigerant flows depending on the season and allows heat to be transferred from the exhaust air to the supply air and vice versa. In this case, the supply and exhaust system can consist of several supply and one exhaust unit of higher capacity, united by one refrigeration circuit. At the same time, the capabilities of the system allow several air handling units to operate in different modes (heating/cooling) simultaneously. The conversion coefficient of the COP heat pump can reach values ​​of 4.5-6.5.


Recuperator with heat pipes.

According to the principle of operation, a recuperator with heat pipes is similar to a recuperator with an intermediate coolant. The only difference is that not heat exchangers are placed in the air flows, but so-called heat pipes or more precisely thermosiphons. Structurally, these are hermetically sealed sections of copper finned pipe, filled inside with a specially selected low-boiling freon. One end of the pipe in the exhaust flow heats up, the freon boils in this place and transfers the heat received from the air to the other end of the pipe, blown by the flow of supply air. Here the freon inside the pipe condenses and transfers heat to the air, which heats up. Mutual mixing of flows, their pollution and transfer of odors are completely excluded. There are no moving elements; pipes are placed in flows only vertically or at a slight slope so that the freon moves inside the pipes from the cold end to the hot end due to gravity. Efficiency rate 50-70%. Important condition to ensure its operation: the air ducts in which the thermosiphons are installed must be located vertically one above the other.


Chamber type recuperator.

The internal volume (chamber) of such a recuperator is divided into two halves by a damper. The damper moves from time to time, thereby changing the direction of movement of the exhaust and supply air flows. The exhaust air heats one half of the chamber, then the damper directs the flow of supply air here and it is heated by the heated walls of the chamber. This process is repeated periodically. The efficiency ratio reaches 70-80%. But the design has moving parts, and therefore there is a high probability of mutual mixing, contamination of flows and transfer of odors.

Calculation of recuperator efficiency.

IN technical specifications For recuperative ventilation units, many manufacturers usually provide two values ​​of the recovery coefficient - based on air temperature and its enthalpy. Calculation of the efficiency of the recuperator can be made by temperature or enthalpy of air. Calculation by temperature takes into account the sensible heat content of the air, and by enthalpy, the moisture content of the air (its relative humidity) is also taken into account. Calculation based on enthalpy is considered more accurate. For the calculation, initial data is required. They are obtained by measuring the temperature and humidity of the air in three places: indoors (where the ventilation unit provides air exchange), outdoors and in the cross section of the supply air distribution grille (from where the processed air enters the room). outside air). The formula for calculating the recovery efficiency by temperature is as follows:

Kt = (T4 – T1) / (T2 – T1), Where

  • Kt– recuperator efficiency coefficient by temperature;
  • T1– outside air temperature, oC;
  • T2– temperature of the exhaust air (i.e. indoor air), °C;
  • T4– supply air temperature, oC.

Enthalpy of air is the heat content of air, i.e. the amount of heat contained in it per 1 kg of dry air. Enthalpy is determined using i-d charts state humid air, putting on it points corresponding to the measured temperature and humidity in the room, outside and supply air. The formula for calculating the recovery efficiency based on enthalpy is as follows:

Kh = (H4 – H1) / (H2 – H1), Where

  • Kh– recuperator efficiency coefficient in terms of enthalpy;
  • H1– enthalpy of outside air, kJ/kg;
  • H2– enthalpy of exhaust air (i.e. indoor air), kJ/kg;
  • H4– enthalpy of supply air, kJ/kg.

Economic feasibility of using air handling units with recovery.

As an example, let’s take a feasibility study for the use of ventilation units with recovery in systems supply and exhaust ventilation car showroom premises.

Initial data:

  • object – car showroom with a total area of ​​2000 m2;
  • the average height of the premises is 3-6 m, consists of two exhibition halls, an office area and a station Maintenance(ONE HUNDRED);
  • for supply and exhaust ventilation of these premises were selected ventilation units duct type: 1 unit with an air flow rate of 650 m3/hour and a power consumption of 0.4 kW and 5 units with an air flow rate of 1500 m3/hour and a power consumption of 0.83 kW.
  • guaranteed range of external air temperatures for duct installations is (-15…+40) оС.

To compare energy consumption, we will calculate the power of a duct electric air heater, which is necessary to heat the outside air in the cold season in a traditional type air-handling unit (consisting of a check valve, a duct filter, a fan and an electric air heater) with an air flow of 650 and 1500 m3/hour, respectively. At the same time, the cost of electricity is 5 rubles per 1 kW*hour.

The outside air must be heated from -15 to +20°C.

The power of the electric air heater was calculated using the heat balance equation:

Qн = G*Cp*T, W, Where:

  • Qn– air heater power, W;
  • G- mass air flow through the air heater, kg/sec;
  • Wed– specific isobaric heat capacity of air. Ср = 1000kJ/kg*K;
  • T– difference in air temperature at the outlet of the air heater and the inlet.

T = 20 – (-15) = 35 oC.

1. 650 / 3600 = 0.181 m3/sec

p = 1.2 kg/m3 – air density.

G = 0.181*1.2 = 0.217 kg/sec

Qn = 0.217*1000*35 = 7600 W.

2. 1500 / 3600 = 0.417 m3/sec

G = 0.417*1.2 = 0.5 kg/sec

Qn = 0.5*1000*35 = 17500 W.

Thus, the use of ducted units with heat recovery in the cold season instead of traditional ones using electric air heaters makes it possible to reduce energy costs with the same amount of supplied air by more than 20 times and thereby reduce costs and accordingly increase the profit of a car dealership. In addition, the use of recovery units makes it possible to reduce the consumer's financial costs for energy resources for heating premises in the cold season and for air conditioning in the warm season by approximately 50%.

For greater clarity, we will carry out a comparative financial analysis of the energy consumption of supply and exhaust ventilation systems for car dealership premises, equipped with duct-type heat recovery units and traditional units with electric air heaters.

Initial data:

System 1.

Installations with heat recovery with a flow rate of 650 m3/hour – 1 unit. and 1500 m3/hour – 5 units.

The total electrical power consumption will be: 0.4 + 5*0.83 = 4.55 kW*hour.

System 2.

Traditional ducted supply and exhaust ventilation units - 1 unit. with a flow rate of 650m3/hour and 5 units. with a flow rate of 1500m3/hour.

The total electrical power of the installation at 650 m3/hour will be:

  • fans – 2*0.155 = 0.31 kW*hour;
  • automation and valve drives – 0.1 kW*hour;
  • electric air heater – 7.6 kW*hour;

Total: 8.01 kW*hour.

The total electrical power of the installation at 1500 m3/hour will be:

  • fans – 2*0.32 = 0.64 kW*hour;
  • automation and valve drives – 0.1 kW*hour;
  • electric air heater – 17.5 kW*hour.

Total: (18.24 kW*hour)*5 = 91.2 kW*hour.

Total: 91.2 + 8.01 = 99.21 kW*hour.

We assume the period of use of heating in ventilation systems is 150 working days per year for 9 hours. We get 150*9 =1350 hours.

Energy consumption of installations with recovery will be: 4.55 * 1350 = 6142.5 kW

Operating costs will be: 5 rubles * 6142.5 kW = 30712.5 rubles. or in relative terms (to the total area of ​​the car dealership of 2000 m2) 30172.5 / 2000 = 15.1 rub./m2.

Energy consumption of traditional systems will be: 99.21 * 1350 = 133933.5 kW Operating costs will be: 5 rubles * 133933.5 kW = 669667.5 rubles. or in relative terms (to the total area of ​​the car dealership of 2000 m2) 669667.5 / 2000 = 334.8 rubles/m2.

When building a house, it is necessary to select and install a system for heat recovery in ventilation systems. There are several modifications of ventilation equipment, which are chosen depending on its manufacturer. Natural impulse equipment includes blower valves for walls and windows to bring fresh air into rooms. Exhaust air ducts are installed to remove odors from toilets, bathrooms, and kitchens.

Air exchange occurs due to the temperature difference between the room and outside. IN summer time temperatures are equalized both inside and outside the rooms. That is, air exchange is suspended. IN winter period the effect manifests itself more quickly, but it will require more energy to heat the cold street air.

A composite hood is a system with forced ventilation and natural air circulation. The disadvantages are:

  • poor air exchange in the house.


    • The advantages include low price and lack of external natural factors. But at the same time, in terms of quality and functionality, aeration cannot be considered full ventilation.

    To provide comfortable conditions in new residential buildings install universal forced aeration systems. Systems with a recuperator provide the supply of fresh air at normal temperature while simultaneously removing exhaust air from the premises. At the same time, heat is removed from the discharge flow.

    Saving thermal energy using supply and exhaust ventilation with a recuperator // FORUMHOUSE

    Depending on the types of recuperators and the size of the premises in which ventilation is installed, the microclimate is improved more or less effectively. But even with the recovery set at a coefficient useful action Just 30% energy savings will be significant, and the overall microclimate in the rooms will also improve. But heat exchangers also have disadvantages:

    • increase in electricity consumption;
    • condensation is released, and in winter icing occurs, which can lead to breakdown of the recuperator;
    • loud noise during operation, causing great inconvenience.

    Heat exchangers or heat exchangers in ventilation systems with enhanced heat and noise insulation operate very quietly.

    Recuperators of directed movement of coolants involve ventilation and disposal of warm exhaust air. The device moves air in two directions at the same speed. Heat exchangers improve the comfort of life in homes.

    At the same time, heating and ventilation costs are significantly reduced, combining both serious processes into one. Such devices can be used both in residential and industrial premises. Thus, the savings Money will be approximately thirty to seventy percent. Heat exchangers can be divided into two groups: heat exchangers simple action and heat pumps to increase the reserve of recovered heat. Heat exchangers can be used only in cases where the resources of the sources are greater than the resources of the microclimate to which the heat energy is transferred.

    Apartment ventilation system with recuperator Ecoluxe EC-900H3.

    Devices that transfer heat from sources to consumers using intermediate working fluids, for example, liquids circulating in closed circuits consisting of circulation pumps, pipelines and heat exchangers located in heated and cooled chambers, are called recuperators with intermediate coolants. Such equipment is widely used in various heat exchangers and circulation pumps at large distances between the heat source and heat consumer.

    This principle is used in an extensive system of heat recovery and energy consumption with different characteristics. The operation of a heat exchanger with an intermediate coolant is that the process in it occurs in the range of water vapor with changes state of aggregation at constant temperature, pressure and volume. The operation of heat pump heat pumps differs in that the movement of the working fluid in them is carried out by a compressor.

    The efficiency of a pipe-in-pipe recuperator in autumn. +6gr.C. on the street.

    Mixed action devices

    For recycling and for warming supply air exchangers of recuperative or contact type are used. Mixed-action devices can also be installed, that is, one with recuperative action, and the second with contact action. It is advisable to install intermediate coolants that are harmless, inexpensive, and do not cause corrosion in pipelines and heat exchangers. Until recently, only water or aqueous glycols acted as intermediate coolants.


    At the moment, their functions are successfully performed by a refrigeration unit, which operates as a heat pump in combination with a recuperator. Heat exchangers are located in the supply and exhaust air ducts, and with the help of a compressor, freon is circulated, the flows of which transfer heat from the exhaust air flow to the supply air flow and back. It all depends on the time of year. Such a system consists of two or more units that are united by one refrigeration circuit, which ensures synchronous operation of the units in different modes.

    Features of plate and rotor designs

    The most simple design at a plate recuperator. The basis of such a heat exchanger is sealed chamber with parallel air ducts. Its channels are separated by steel or aluminum heat-conducting plates. The disadvantage of this model is the formation of condensation in the exhaust ducts and the appearance of an ice crust in winter time. When defrosting equipment, incoming air goes to the heat exchanger, and warm outgoing air masses help melt the ice on the plates. To prevent such situations, it is preferable to use plates made of aluminum foil, plastic or cellulose.

    Rotary recuperators are the most highly efficient devices and are cylinders with corrugated metal layers. When the drum set rotates, a warm or cold air stream enters each section. Since the efficiency is determined by the rate of rotation of the rotor, such a device can be controlled.


    The advantages include heat recovery of approximately 90%, economical consumption of electricity, air humidification, as soon as possible payback. To calculate the efficiency of the recuperator, it is necessary to measure the air temperature and calculate the enthalpy of the entire system using the formula: H = U + PV (U - internal energy; P - pressure in the system; V - volume of the system).

    Recovery(from Lat. recuperatio - “return receipt”) - return of part of materials or energy for reuse in the same technological process.

    Recovery during processing of raw materials is called desorption. Desorption, like other mass transfer processes, is usually reversible, and the primary process is called adsorption. These processes are widely used in the chemical industry for purification and drying of gases, purification and clarification of solutions, separation of mixtures of gases or vapors, in particular when extracting volatile solvents from a mixture of gases (recovery of volatile solvents). Recovery of liquid solvents is used in the production of hydrocarbons, alcohols, ethers and esters, etc. Adsorption and desorption processes are carried out in specialized adsorption units.

    Recovery– the process of partial energy recovery for reuse. In this topic we are talking about air recovery in ventilation systems.

    The principle of operation of the recuperator

    We have supply and exhaust ventilation. In winter, the supply air is cleaned by air filters and heated by air heaters. It enters the room, warms it and dilutes harmful gases, dust and other emissions. Then it enters the exhaust ventilation and is thrown out into the street... Hence the thought... Why don't we heat the cold supply air with the exhaust air. After all, we are essentially throwing money away. So, we have exhaust air with a temperature of 21 C and supply air, which before the heater has a temperature of -10 C. We install, for example, a recuperator with a plate heat exchanger. To understand the principle of operation of a recuperator with a plate heat exchanger, imagine a square in which the exhaust air passes from bottom to top, and the supply air from left to right. Moreover, these flows do not mix with each other due to the use of special heat-conducting plates that separate these two flows.

    As a result, the exhaust air gives up to 70% of the heat to the supply air and at the outlet of the recuperator has a temperature of 2-6 C, and the supply air, in turn, has a temperature at the outlet of the recuperator of 12-16 C. Consequently, the heater will not heat the air -10 C , and +12 C and this will allow us to significantly save on electrical or thermal energy spent on heating the supply air.

    Types of recuperators

    Although a recuperator with a plate heat exchanger is most common in the Russian Federation, there are other types of recuperators, which in some cases are more efficient or, in general, only they can cope with the tasks. We invite you to consider the four most popular types of recuperators:

      Recuperator with plate heat exchanger (Plate recuperator)

      Recuperator with rotary heat exchanger (Rotary recuperator)

      Water recirculation heat exchanger

      Roof recuperator

    Plate recuperator

    The most common type is a plate or cross-flow air recuperator for apartments.

    It is a small cassette. Two channels are created in it, which are separated from each other by sheets of steel. They carry separate supply and exhaust air flows. Steel acts as a heat “filter”. That is, a temperature exchange occurs, but air mixing is not allowed. The prevalence of this type of device is due to its simplicity, compactness and low cost. The plate air recuperator for apartments has some disadvantages, but they are not so significant when installed in small residential premises.

    Advantages: - the device is easily built into any part of the air duct; - there are no moving parts (easier maintenance, no risk of air flow displacement, etc.); - relatively high efficiency – 50...90%; - can work with high-temperature gas and air mixtures (up to +200°C); - aerodynamic resistance to passing air flows increases slightly; - simple performance adjustment via a bypass valve.

    Plate recuperators are designed in such a way that the air flows in them do not mix, but contact each other through the walls of the heat exchange cassette. This cassette consists of many plates that separate cold air flows from warm ones. Most often, the plates are made of aluminum foil, which has excellent thermal conductivity properties. The plates can also be made of special plastic. These are more expensive than aluminum ones, but increase the efficiency of the equipment.

    Plate heat exchangers have a significant drawback: as a result of the temperature difference, condensation forms on cold surfaces, which turns into ice. An ice-covered recuperator stops working effectively. To defrost it, the incoming flow is automatically bypassed by the heat exchanger and heated by a heater. Meanwhile, the escaping warm air melts the ice on the plates. In this mode, of course, there is no energy saving, and the defrosting period can take from 5 to 25 minutes per hour. To heat the incoming air during the defrosting phase, air heaters with a power of 1-5 kW are used.

    Some plate heat exchangers use preheating of the incoming air to a temperature that prevents the formation of ice. This reduces the efficiency of the recuperator by approximately 20%.

    Another solution to the icing problem is hygroscopic cellulose cassettes. This material absorbs moisture from the exhaust air flow and transfers it to the incoming air, thereby returning moisture back. Such recuperators are justified only in buildings where there is no problem of air humidification. The undoubted advantage of hygrocellulose recuperators is that they do not require electrical heating of the air, which means they are more economical. Recuperators with double plate heat exchangers have an efficiency of up to 90%. Ice does not form in them due to heat transfer through the intermediate zone.

    Well-known manufacturers of plate heat exchangers: SCHRAG (Germany), MITSUBISHI (Japan), ELECTROLUX, SYSTEMAIR (Sweden), SHUFT (Denmark), REMAK, 2W (Czech Republic), MIDEA (China).

    Electric motors are designed to drive various mechanisms, but after completing the movement, the mechanism must be stopped. For this you can also use electric car and recovery method. This article explains what energy recovery is.

    What is recovery

    The name of this process comes from the Latin word “recuperatio”, which translates as “receiving back”. This is the return of some of the energy or materials used for reuse.

    This process is widely used in electric vehicles, especially those powered by batteries. When driving downhill and during braking, the recuperation system returns the kinetic energy of movement back to the battery, recharging them. This allows you to travel a longer distance without recharging.

    Regenerative braking

    One type of braking is regenerative. In this case, the rotation speed of the electric motor is greater than that specified by the network parameters: the voltage on the armature and the field winding in the motors direct current or the frequency of the supply voltage in synchronous or asynchronous motors. In this case, the electric motor switches to generator mode and releases the generated energy back into the network.

    The main advantage of the recuperator is energy saving. This is especially noticeable when driving around the city with constantly changing speeds, commuter electric transport and subways with a large number of stops and braking in front of them.

    In addition to its advantages, recovery has disadvantages:

    • impossibility of completely stopping transport;
    • slow stop at low speeds;
    • lack of braking force when parking.

    To compensate for these shortcomings, vehicles are equipped with an additional mechanical brake system.

    How does the recovery system work?

    To operate, this system must provide power to the electric motor and return energy during braking. This is most easily done in urban electric vehicles, as well as in older electric vehicles equipped with lead batteries, DC motors and contactors - when switching to a lower gear when high speed Energy recovery mode is activated automatically.

    In modern transport, a PWM controller is used instead of contactors. This device allows you to return energy to both direct and alternating current networks. During operation, it acts as a rectifier, and during braking it determines the frequency and phase of the network, creating a reverse current.

    Interesting. When dynamic braking of DC electric motors occurs, they also switch to generator mode, but the generated energy is not returned to the network, but is dissipated in the additional resistance.

    Power descent

    In addition to braking, the recuperator is used to reduce speed when lowering loads using lifting mechanisms and when driving down an inclined road of electric vehicles. This eliminates the need to use a wear-out mechanical brake.

    Application of recovery in transport

    This braking method has been used for many years. Depending on the type of transport, its application has its own characteristics.

    In electric cars and electric bicycles

    When driving on the road, and even more so off-road, the electric drive operates almost all the time in traction mode, and before stopping or at an intersection - “coasting”. Stopping is done using mechanical brakes due to the fact that recuperation is ineffective at low speeds.

    In addition, the efficiency of batteries in the charge-discharge cycle is far from 100%. Therefore, although such systems are installed on electric vehicles, they do not provide great battery savings.

    On the railway

    Recuperation in electric locomotives is carried out by traction motors. At the same time, they turn on in generator mode, converting the kinetic energy of the train into electricity. This energy is given back to the network, in contrast to rheostatic braking, which causes the rheostats to heat up.

    Recuperation is also used during long downhill runs to maintain a constant speed. This method saves electricity, which is fed back into the grid and used by other trains.

    Previously, only locomotives operating on DC power were equipped with this system. In devices operating from an alternating current network, it is difficult to synchronize the frequency of the supplied energy with the frequency of the network. Now this problem is solved using thyristor converters.

    In the underground

    In the subway, while trains are moving, cars are constantly accelerating and braking. Therefore, energy recovery has a great economic effect. It reaches a maximum if this happens simultaneously in different trains at the same station. This is taken into account when creating the schedule.

    In city public transport

    In urban electric transport, this system is installed in almost all models. It is used as the main one up to a speed of 1-2 km/h, after which it becomes ineffective and the parking brake is activated instead.

    In Formula 1

    Since 2009, some cars have been equipped with a recovery system. This year, such devices have not yet provided tangible superiority.

    In 2010, such systems were not used. Their installation, with restrictions on power and volume of recovered energy, resumed in 2011.

    Braking of asynchronous motors

    Reducing the speed of asynchronous electric motors is carried out in three ways:

    • recovery;
    • opposition;
    • dynamic.

    Regenerative braking of an asynchronous motor

    Recovery asynchronous motors possible in three cases:

    • Changing the frequency of the supply voltage. Possible when powering the electric motor from a frequency converter. To switch to braking mode, the frequency is reduced so that the rotor rotation speed is greater than synchronous;
    • Switching windings and changing the number of poles. Possible only in two- and multi-speed electric motors, in which several speeds are provided structurally;
    • Power descent. Applicable in lifting mechanisms. These devices are equipped with electric motors with a wound rotor, the speed of which is adjusted by changing the value of the resistance connected to the rotor windings.

    In any case, when braking, the rotor begins to overtake the stator field, the slip becomes greater than 1, and the electric machine begins to work as a generator, delivering energy to the network.

    Opposition

    The counter-switching mode is carried out by switching the two phases powering the electric machine between each other and turning on the rotation of the device in the opposite direction.

    It is possible to switch on with counter-connection of additional resistances in the stator circuit or wound rotor windings. This reduces current and braking torque.

    Important! In practice, this method is rarely used due to currents exceeding 8-10 times higher than rated (with the exception of motors with wound rotor). In addition, the device must be turned off in time, otherwise it will begin to rotate in the opposite direction.

    Dynamic braking of an asynchronous motor

    This method is carried out by applying a constant voltage to the stator winding. To ensure trouble-free operation of the electric machine, the braking current should not exceed 4-5 currents idle move. This is achieved by including additional resistance in the stator circuit or using a step-down transformer.

    Direct current flowing in the stator windings creates a magnetic field. When it crosses, an EMF is induced in the rotor windings and current flows. The released power creates a braking torque, the strength of which is greater, the higher the rotation speed of the electric machine.

    Actually asynchronous electric motor in dynamic braking mode it turns into a direct current generator, the output terminals of which are short-circuited (in a machine with a squirrel-cage rotor) or connected to additional resistance (an electric machine with a wound rotor).

    Recovery in electrical machines- This is a type of braking that allows you to save energy and avoid wear and tear on mechanical brakes.

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