Electromagnetic drive: types, purpose, principle of operation

Today, almost all areas of human activity from heavy industry to transport and household services are interested in the use of compact, productive and functional drive mechanisms. This is the reason for the constant improvement of traditional power unit concepts, which, although they are improved, do not change the fundamental design. The most popular basic systems of this type include an electromagnetic drive, the working mechanism of which is used in both large-format equipment and small technical devices.

Drive purpose

In almost all target applications, this mechanism acts as the executive body of the system. Another thing is that the nature of the function performed and the degree of its responsibility within the overall work process may change. For example, in shut-off valves, this actuator is responsible for the current position of the valve. In particular, due to its force, the overlap takes the position of a normally closed or open state. Such devices are used in various communication systems, which determines both the operating principle and the protective characteristics of the device. In particular, the electromagnetic smoke removal drive is included in the infrastructure of the fire safety system, being structurally connected to the ventilation ducts. The drive housing and its critical working parts must be resistant to high temperatures and harmful contacts with thermally hazardous gases. As for the execution command, the automation is usually triggered when signs of smoke are detected. The drive in this case is a technical means of regulating the flow of smoke and fumes.

A more complex configuration of the use of electromagnetic actuators occurs in multi-way valves. These are a kind of collector or distribution systems, the difficulty of managing which lies in the simultaneous control of entire groups of functional units. Such systems use an electromagnetic valve drive with the function of switching flows through the nozzles. The reason for closing or opening the channel can be certain values ​​of the working medium (pressure, temperature), flow intensity, software time settings, etc.

Operating principle and operating features of valves with pneumatic drive

2.1. Design of angle seat valves with pneumatic drive

The design of a pneumatically actuated globe valve is shown in Figure 10.

Figure 10 – Design of a seat valve with a pneumatic drive

Inside the pneumatic drive housing (1) there is a piston (2), which is tightly adjacent to the walls of the pneumatic drive due to the seal (3). Under the action of the spring (4), the piston takes a position corresponding to the initial state of the pneumatic valve (closed for NC valves and open for NO valves). A rod (5) with a disk (6) is rigidly fixed to the piston. When closed, the disc is securely pressed against the seat (7) and ensures the tightness of the valve. Most air actuated valves have a visual indicator (8) mechanically linked to the valve piston.

To open the valve (see Figure 11), it is necessary to supply compressed air to the pneumatic actuator. The pneumatic valve opens under the action of compressed air, which moves the piston and rod upward, which also leads to compression of the spring.

Figure 11 – Valve with pneumatic actuator in open state

To close the valve, it is enough to bleed air from the pneumatic actuator. The piston moves down under the action of a spring, pressing the disk against the seat.

The valve with a pneumatic drive is opened only by compressed air pressure, and closed by a powerful spring. Thus, the operation of valves with a pneumatic drive is significantly less dependent on the parameters of the medium passing through it, in contrast to solenoid valves.

Examples of pneumatic actuated angle valves

• valves with pneumatic actuator VALMA ASV series
• ASCO Series 290 Air Actuated Valves

2.2. Pneumatic valve control diagram

To control pneumatic valves, special solenoid valves called pilot or control valves are used. These valves are so called because they not only shut off the supply of the working fluid, but also redistribute it between various inlet and outlet ports.

To control pneumatically driven valves, 3/2 type distribution valves are used, the operating diagram of which is shown in Figure 12.

Figure 12 – Pneumatic diagram of distributor 3/2

Port 1 is connected to the input port of the pneumatic actuator, the compressed air supply is connected to port 2, and port 3 remains open and is used for exhaust - releasing air from the pneumatic actuator into the atmosphere when the pneumatic actuator valve is closed.

As long as the control valve coil is de-energized, port 1 is connected to port 3 and port 2 is closed. Thus, compressed air does not enter the pneumatic drive, and the pneumatic drive itself is connected to the atmosphere - the valve with the pneumatic drive is closed.

When voltage is applied to the coil, port 1 is connected to port 2, and port 3 is closed. Compressed air enters the pneumatic actuator, due to which the pneumatic valve opens.

Figure 13 shows 3/2 control solenoid valves of various designs.

Figure 13 – 3/2 distribution valves of various designs

For the valve shown on the left, the exhaust to atmosphere passes through the core tube. The valve pictured on the right has air and exhaust ports on the top and bottom of the valve.

Figure 14 shows a generalized control diagram for a pneumatically actuated valve.

Figure 14 – Generalized control diagram for a valve with a pneumatic drive

An electrical signal from the control system is sent to the distribution valve (2), which controls the flow of compressed air, supplying it to the pneumatic valve (1). The required degree of air purification and pressure stabilization is provided by the filter-regulator (3).

Control valves can be mounted directly on the air-actuated valve (see Figure 15) or separately in the control cabinet (see Figure 16).

Figure 15 – Installation of a pilot valve on a valve with a pneumatic actuator

Figure 16 – Installation of distribution valves in the control cabinet

Each of these installation methods has its own advantages and disadvantages.

Installation of distributors on pneumatic valves

Advantages

1. +
   The valve response time is shorter (since air enters directly into the pneumatic actuator).
2. +
   Higher energy efficiency due to saving compressed air (each time a valve with a pneumatic drive is activated, all the air after the distribution valve is discharged into the atmosphere; when the distributor is mounted directly on the valve drive, there is no pneumatic tube between them, therefore the consumed volume of compressed air is lower).

Flaws

1. —
   The need to lay two lines to the valve: pneumatic and electric.
2. —
   The distributor is located near the pneumatically actuated valve, where it may be exposed to negative environmental influences.

Installation of distributors in the control cabinet

Advantages

1. +
   Simplification of wiring of electrical circuits (all distributors are in one cabinet, only one line is laid to the valve with a pneumatic drive - pneumatic).
2. +
   All distributors are easily accessible for maintenance, as they are located in the control cabinet.
3. +
   All distributors are reliably protected from environmental influences (high temperature, dust, washing equipment with chemicals, and so on).

Flaws

1. —
   Longer response time for valves with pneumatic actuators.
2. —
   Increased air consumption.

Construction and components

The central working element of the drive is the solenoid unit, which is formed by a hollow coil and a magnetic core. The electromagnetic communication of this component with other parts is provided by small internal fittings with control pulse valves. In its normal state, the core is supported by a spring with a rod that rests on the seat. In addition, a typical electromagnetic drive device provides for the presence of a so-called manual override of the working part, which takes over the functions of the mechanism in moments of sudden changes or complete absence of voltage. Additional functionality may also be provided, provided by signaling means, auxiliary locking elements and core position clamps. But since one of the advantages of drives of this type is their small size, for optimization purposes, developers try to eliminate excessive saturation of the design with secondary devices.

How does a solenoid valve work?

The solenoid valve consists of:

• steel, cast iron, brass or polymer housings;
• induction coil with core (solenoid);
• working locking element;
• seal;
• damping spring.

The copper induction coil inside the shut-off device is located in a sealed housing, where access to water is closed. The blocking or opening of the working medium current channel occurs due to the rod and membrane extending under the action of the solenoid.

The power supply to the solenoid valve is connected via terminals on the top of the device body next to the induction coil

In a de-energized state, under the influence of a spring, the valve completely shuts off the current channel or leaves it completely open. Further, after applying voltage to the coil, the core and the rod are displaced, as a result of which the cross-section of this duct increases/decreases.

The general principle of operation of the electromagnetic valve under consideration is simple - the movement of the rod occurs in it due to electromagnetic induction. When electric current flows through the coil, the core located in its center is affected by an electromagnetic field, the strength and direction of which depend on the applied voltage in volts.

As a result, the shut-off element is displaced and the flow area of ​​the valve changes.

The solenoid valve coil, depending on the modification of the device, can operate on a voltage of 5–36 V DC or 220 V AC

Electrovalves with low control voltage are designed to operate in small diameter pipelines and with low pressure of the working medium. The scope of their application is quite limited.

But such valves are easier to integrate into a control system on low-voltage semiconductor devices and connect to various microcontrollers. They are usually used in water supply systems and heating circuits of private houses.

The principle of operation of the mechanism

In both magnetic and electromagnetic power devices, the role of the active medium is played by the magnetic flux. To form it, either a permanent magnet or a similar device is used with the ability to point-to-point or disable its activity by changing the electrical signal. The actuator begins to operate from the moment voltage is applied, when current begins to flow through the solenoid circuits. In turn, as the magnetic field activity increases, the core begins to move relative to the cavity of the inductor. Actually, the operating principle of an electromagnetic drive boils down to the conversion of electrical energy into mechanical energy through a magnetic field. And as soon as the voltage drops, the forces of the elastic spring come into play, which returns the core to its place and the drive armature assumes its original normal position. Also, to regulate individual stages of force transmission in complex multi-stage drives, pneumatic or hydraulic drives can be additionally activated. In particular, they make possible the primary generation of electricity from alternative energy sources (water, wind, sun), which reduces the cost of the equipment’s operating process.

Actuating actions of the electromagnetic drive

The movement pattern of the drive core and its ability to work as an output power unit determine the features of the actions that the mechanism can perform. It should be noted right away that in most cases these are devices with the same type of elementary movements of the executive mechanics, which are rarely supplemented with auxiliary technical functions. Based on this feature, the electromagnetic drive is divided into the following types:

• Turning. In the process of applying current, the power element is triggered, which rotates. Such mechanisms are used in ball and plug valves, as well as in butterfly valve systems.
• Reversible. In addition to the main action, it is capable of providing a change in the directions of the power element. More common in control valves.
• Pushing. This electromagnetic actuator performs a pushing action, which is also used in control valves and shut-off valves.

From the point of view of the design solution, the power element and the core may well be different parts, which increases the reliability and durability of the device. Another thing is that the optimization principle requires combining several tasks within the functionality of one technical component in order to save space and energy resources.

Selecting a solenoid valve: device prices and popular brands

When selecting shut-off valves for a water supply system, you must carefully study the specifications and descriptions provided by the manufacturer. This information will allow you to determine under what conditions the installation of a particular valve model is permissible.

When choosing a valve for a water supply system, you need to pay attention to the dimensions of the outlet and inlet holes.

When choosing a device, you need to take into account the following points:

• system type;
• temperature regime;
• pressure level;
• chemical composition of the liquid;
• current speed, etc.

The dimensions of the outlet and inlet openings are of considerable importance. These parameters must correspond to the diameter of the pipes. It is very important that the characteristics of the system and shut-off valves match, otherwise disruptions in the hydraulics of communications may occur. This outcome is possible if, in the area where the valve is installed, the flow of liquid slows down due to a narrow hole, which will inevitably affect the pressure level and temperature in the entire pipeline.

Solenoid valve prices:

Danfoss solenoid valves

Danfoss valves are equipped with various types of equipment - from pumps installed at gas stations, to machines that can be found in dry cleaners. The small size of these devices does not at all affect their level of reliability. Danfoss produces a wide range of valves. Thanks to this, in stores you can find modifications that other manufacturers produce exclusively on special order.

Danfoss solenoid valves are small in size, but this does not affect their level of reliability at all

Advantages of Danfoss solenoid valves:

• a wide range of general purpose devices;
• even standard modifications can solve many problems faced by the industry;
• The product range allows you to select devices that can come into contact with very aggressive media, for example, valves whose body is made of stainless steel and is provided with protection class IP67.

Note! If necessary, Danfoss may modify products based on the buyer's specifications. Thanks to this, you can find optimal solutions for any industrial task. Moreover, representatives of the purchasing company can take part in the development process.

The shut-off devices come with a complete technical documentation package and also provide simplified guides to help customers select the valve with the right characteristics. The production process involves specialists who are experts in the regulation of gas, steam and liquids. Therefore, the products are characterized by high functionality, reliability and safety.

Danfoss produces both direct-acting and servo-operated solenoid valves

On sale you can find direct acting electromagnetic locking devices equipped with a servo drive. Danfoss EV220B two-way solenoid valves, which are designed to regulate neutral gases, water, air, and oils, are in particular demand. Some modifications from this line can control steam and mildly aggressive environments.

Features of Asco solenoid valves

The American company Asco is one of the leading manufacturers of hydropneumatic, electromagnetic and shut-off valves, as well as pneumatic cylinders, pneumatic automation and other automation devices.

Product advantages:

• instrumentation equipment is manufactured on modern production lines with a wide range of functionality;
• if necessary, the valves can be easily repaired, and the process itself does not take much time;
• high level of reliability;
• ability to withstand contact with aggressive environments and extreme loads.

The manufacturer produces more than 5,000 standard types of shut-off valves. In addition, Asco produces special modifications and versions of these devices, the number of which exceeds 20,000. All of them are designed to meet the different needs of customers. At the same time, the manufacturer complies with the strictest quality requirements, monitoring all stages of production, including the development process, sales, and service.

The quality of Asco solenoid valves is confirmed by ISO 9002 and 9001 certificates

Note! Before hitting store shelves, products are carefully checked for manufacturing defects and are also tested. The highest quality of the valves is confirmed by ISO 9002 and 9001 certificates.

Arcom Products: AR HX 3 Solenoid Valve Specifications

Arcom supplies the market with thousands of items of electrical equipment. This list includes recorders (paperless and paper), controllers, electrical and measuring instruments, various tools and related accessories. Solenoid valves occupy a special place in the range. Buyers can purchase more than 4,500 locking device options at an affordable price. Moreover, all products are certified and meet a high level of quality.

In the manufacturer's catalogs you can select fittings that allow you to control the movement of water, air and petroleum products. In addition, the manufacturer provides a huge selection of spare parts, relays, coils, connectors and valves for these devices.

Despite the extensive range, special attention is paid to solenoid valves; the HX 3 solenoid valve, due to its many advantages, is considered the most popular model:

Solenoid valve AR HX 3 is designed to regulate steam, air, hot and cold water

• durable, durable stainless steel case;
• fast response (reacts when the pressure reaches zero);
• minimum sizes;
• ability to connect to sensors.

This model is designed to regulate hot and cold water, steam and air, which allows you to install the valve even in electric irons, coffee machines and other devices that use steam in their work.

Electromagnetic fittings

The drive actuators can operate in different configurations, performing certain actions required for the operation of a specific operating infrastructure. But in any case, the function of the core or power element alone will not be enough to provide a sufficient effect in terms of performing the final task, with rare exceptions. In most cases, a transition link is also required - a kind of translator of the generated mechanical energy from the direct drive mechanics to the target device. For example, in an all-wheel drive system, the electromagnetic clutch acts not just as a force transmitter, but as a motor that rigidly connects the two parts of the shaft. Asynchronous mechanisms even have their own excitation coil with pronounced poles. The leading part of such couplings is made according to the principles of the rotor winding of an electric motor, which completely gives this element the functions of a converter and force translator.

In simpler direct-acting systems, the task of transmitting force is performed by standard ball bearing devices, hinge and distribution units. The specific design and configuration of the action, as well as the relationship with the drive system, are implemented in different ways. Individual schemes for interfacing components with each other are often developed. In the same electromagnetic drive coupling, an entire infrastructure is organized with its own metal shaft, slip rings, collectors and copper bars. And this is not counting the parallel arrangement of electromagnetic channels with pole pieces and contours for the direction of magnetic field lines.

Drive operating parameters

The same design with a typical operating scheme may require the connection of different powers. Also, typical models of drive systems differ in power load, type of current, voltage, etc. The simplest electromagnetic valve drive operates from a 220 V network, but there may also be models with a similar design, but requiring connection to three-phase industrial networks at 380 V. Power supply requirements are determined by the size of the device and the operating characteristics of the core. The number of engine revolutions, for example, directly determines the amount of power consumed, and with it the insulation properties, windings and resistance parameters. If we talk specifically about industrial electrical infrastructure, then in the project for integrating a powerful drive, traction forces, the characteristics of the grounding loop, the implementation diagram of circuit safety devices, etc. must be calculated.

Block drive systems

The most common design form factor for the release of drive mechanisms based on the electromagnetic operating principle is block (or aggregate). This is an independent and partially isolated device, which is mounted on the body of the target mechanism or also on a separate actuator unit. The fundamental difference between such systems is that their surfaces do not come into any contact with the cavities of the transition power links, and especially the working elements of the executive bodies of the target equipment. At the very least, such contacts do not require any measures to be taken to protect both structures. The block type of electromagnetic drive is used in cases where functional units need to be isolated from the negative influence of the working environment - for example, from the risks of corrosion or temperature effects. To provide a mechanical connection, the same isolated valve body, like a rod, is used.

Why is a solenoid valve needed?

Solenoid valves are a category of modern shut-off valves for pipelines for a wide variety of purposes. In everyday life, such electric valves are used in cars, special equipment, water supply systems and automatic watering and heating systems.

They are also widely used in industry to regulate current and control the transport of a variety of liquids and gases.

The solenoid valve is a volatile equipment; it requires power to open or close.

The solenoid valve for water or gas does not have any sensors inside. With its help, you can only regulate or completely block the flow of the working environment. If automation of these processes is required, then you will have to additionally install external measuring instruments, tying the operation of the electrovalve to them.

For example, use an additional controller and a water leakage sensor in combination, so that when a leak is detected, the solenoid valve receives the appropriate command from the controller and shuts off the pipeline.

The advantages of using solenoid valves include:

• quick adjustment of the working medium current through the pipeline;
• versatility and reliability of the device;
• long service life;
• small size and light weight;
• variety of instrument types.

The valve operates literally within a split second after the signal is given. It is designed to work with liquids under different pressures, from 0 to 25 bar, and with varying temperatures, from -20 to +120 ° C. At the same time, in a de-energized state, such an electric valve can remain either in a closed or open position - it all depends on the modification of the device.

Most often in everyday life, a solenoid solenoid valve is used in water supply and heating systems, where it is used to remotely regulate the water flow

In water supply systems, it allows you to automatically shut off the water supply if the pipes burst. And in heating systems, such a valve is used as a device for regulating the flow of coolant.

Here, using an external temperature sensor, it independently reduces or increases the flow of heated liquid from the boiler to the radiators.

Features of the built-in drive

A type of electromagnetic power drives that act as an integral part of the working system, forming a single communication infrastructure with it. As a rule, such devices have compact dimensions and low weight, which allows them to be integrated into a wide variety of engineering structures without significantly affecting their functional and ergonomic characteristics. On the other hand, size optimization and the need to expand the possibilities for strapping (direct connection to equipment) limit the creators in ensuring a high degree of security for such mechanisms. Therefore, standard low-cost insulating solutions such as sealed separation tubes are being considered to help protect sensitive elements from the aggressive effects of the working environment. Exceptions include vacuum valves with an electromagnetic drive in a metal casing, to which fittings made of high-strength plastic are connected. But these are already specialized enlarged models that have comprehensive protection against toxic, thermal and mechanical factors.

Areas of application of the device

With the help of this drive, problems of power mechanical support of various levels are solved. In the most critical and complex systems, sealless fittings are used to control electromagnetic devices, which increases the reliability and performance of the equipment. In this combination, units are used in transport and communication pipeline networks, when servicing storage facilities for petroleum products, in the chemical industry, at processing stations and plants in various industries. If we talk about simple devices, then an electromagnetic fan drive for supply and exhaust systems is common in the domestic sphere. Small-format mechanisms also find their place in sanitary fittings, pumps, compressors, etc.

Advantages and disadvantages

The main advantages of EM drives are:

• simplicity of design and application;
• durability and reliability;
• speed and great functionality;
• unpretentiousness, uninterrupted operation in the most difficult conditions;
• light weight, compactness;
• filigree precision;
• maximum ease of automation and maintenance;
• low power consumption;
• minimum number of moving elements.

The electromagnetic drive has practically no alternative devices used to control sealless valves installed in pipelines transporting explosive, toxic, radioactive and aggressive media. Such fittings meet increased tightness requirements and are used in the nuclear industry, oil and gas and chemical industries, and cryogenic technology.

The development of technology and the complication of operating conditions for industrial equipment determine the active use of EM drives in pipeline fittings. Electromagnetic fittings are ideally combined with automatic control systems. Therefore, in the future, with the development of technical progress, the demand for electromagnetic drives for pipeline fittings will only increase, gradually displacing pipeline fittings with electric drives (for example: gate valves, ball valves, valves, butterfly valves with electric drive, etc.)
22.08.2018