The energy efficiency of equipment largely depends on the energy efficiency of the components and technical solutions used in it. Recently, applications in compressors, pumps and fans of variable speed motors have become popular.

Increase efficiency by optimizing the components used

Along with highly efficient induction motors, motors with permanent magnet rotors, which have a high efficiency, are now widely used. Motors using this technology are widely known in the HVAC industry as electronically commutated (EC) motors. Typically, EC motors are used in external rotor fans.

In order to use EC technology in a variety of industries, Danfoss has taken the time-tested VVC+ algorithm and optimized it to work with permanent magnet synchronous motors. The efficiency of this type of motors, often referred to as permanent magnet motors (PM) for short, is comparable to that of EC motors. At the same time, the design of PM motors complies with IEC standards, which makes it easy to integrate them into both new and existing systems and greatly simplifies the commissioning of motors.

Danfoss EC+ technology allows the use of IEC compliant PM motors with Danfoss VLT frequency converters.

Energy efficiency standards

Increasing system efficiency is an easy way to reduce system power consumption. For this reason, the European Union has approved minimum energy efficiency standards for a number of technical devices. So, for three-phase induction motors, the minimum energy efficiency standard (MEPS) has been introduced (see table).

Table. MEPS standards for electric motors

However, to achieve maximum energy efficiency, attention must be paid to the performance of the system as a whole. For example, frequent start/stop cycles on IE2 motors result in an increase in energy consumption that negates the savings achieved in normal operation.

Particular attention must also be paid to fans and pumps. The use of a frequency converter in conjunction with devices of this type allows you to achieve higher efficiency. Thus, the determining factor is the overall performance of the system, not the performance of individual components. According to VDI DIN 6014, the efficiency of a system is defined as the product of the efficiency of its component parts:

System Efficiency = Drive Efficiency × Motor Efficiency × Connection Efficiency × Fan Efficiency.

As an example, consider the efficiency of an external rotor centrifugal fan used in conjunction with an EC motor. To achieve a compact system size, the motor is partly located inside the fan impeller. Such a scheme reduces the performance of the fan and the efficiency of the system as a whole. Thus, the high efficiency of the engine does not at all guarantee the high efficiency of the entire system (Fig. 1).

Rice. 1. Efficiency of various systems using a centrifugal fan with a diameter of 450 mm. The efficiency of motors is determined during measurements. Fan efficiency obtained from manufacturer's catalogs

How an EC motor works

In the HVAC industry, an EC motor is generally understood to be a special type of motor that has a compact size and high efficiency. EC motors operate on the principle of electronic commutation instead of the traditional brush commutation found in DC motors. Manufacturers of EC motors replace the rotor winding with permanent magnets. The magnets improve efficiency, while the electronic commutation eliminates the problem of mechanical wear on the brushes. Since the principle of operation of an EC motor is similar to that of a DC motor, such motors are often referred to as brushless DC motors (BLDC).

Motors of this class usually have a power of up to several hundred watts. In the ventilation and air conditioning industry, they are most often used as external rotary motors and are used in a wide power range. The power of some devices can reach 6 kW.

Rice. 2. Various types of motors

Thanks to the built-in permanent magnets, permanent magnet motors do not require a separate winding for excitation. However, they require an electronic controller to operate, which generates a rotating field. Connecting directly to the power line is usually not possible or results in reduced efficiency. To control the motor, the controller (frequency converter) must be able to determine the current state of the rotor at any time. For this purpose, two different methods are used, one of which uses feedback from the sensor to determine the current position of the rotor, and the other does not use it.

Rice. 3. Comparison of different types of switching

A distinctive feature of a motor with excitation from permanent magnets is the nature of the reverse electromotive force (EMF). In generator mode, the motor generates a voltage called back EMF. For optimal motor control, the controller must match the input voltage waveform as closely as possible to the back EMF waveform. Manufacturers of brushless DC motors use square-wave switching for this purpose (Figure 3).

PM motors as an alternative to EC motors

Each type of permanent magnet motor has its own advantages and disadvantages. Sine-wave commutated PM motors are structurally simpler, but require more complex control circuitry. In the case of EC motors, the situation is diametrically opposite: creating a square wave back EMF signal is more difficult, but the structure of the control circuit is greatly simplified. However, electronic switching technology has a higher torque ripple due to the use of square wave switching. This type of motor also uses 1.22 times higher voltage than PM motors due to the use of two phases instead of three.

Rice. 4. Equivalent circuits of engines

The use of permanent magnets in the motor (Fig. 4) almost completely eliminates losses on the rotor, which leads to increased efficiency.

The efficiency advantages of EC motors compared to traditional single-phase shaded-pole induction motors are most significant in the power range of several hundred watts. Three-phase induction motors typically have power in excess of 750W. The efficiency advantage of EC motors decreases as the power rating of the equipment increases. Systems based on EC motors and PM motors (electronics plus motor) with similar configurations (power supply, EMC filter, etc.) have comparable efficiencies.

Three-phase induction motors are now widely used with standard installation and frame dimensions defined in IEC EN 50487 or IEC 72. However, many PM motors use other standards. Servo drives are a typical example. With a compact size and long rotor, the servo drives are optimized for high dynamic applications.

PM motors are now available in standard IEC frame sizes, allowing high efficiency permanent magnet motors to be used in existing systems. This allows older three-phase induction motors (TPIM) to be replaced by more efficient PM motors.

There are two types of PM motors according to IEC standards:

Option 1: PM/EC and TPIM motors have the same frame size.

Example. The 3kW TPIM motor can be replaced by an EC/PM motor of the same size.

Option 2: PM/EC motor with optimized frame size and TPIM motor have the same power rating. Due to the fact that PM motors are usually more compact at a comparable power level, the frame size is smaller than for a TPIM type motor.

Example. The 3 kW TPIM type motor can be replaced by an EC/PM type motor with a frame size corresponding to the 1.5 kW TPIM type motor.

EC+ technology

Danfoss EC+ technology was born in response to customer requirements. It allows you to use PM-motors together with Danfoss frequency converters. Customers have the opportunity to choose an engine from any manufacturer. Thus, they get all the benefits of EC technology at a relatively low cost, without losing the ability to optimize the entire system as needed.

Combining the most efficient individual components within a single system also provides a range of benefits. By using standard components, customers are independent of suppliers and have free access to spare parts. It is not necessary to adjust the installation connections when replacing the motor. Commissioning the motor is similar to commissioning a standard three-phase induction motor.

Benefits of EC+ technology

Rice. 5. Size comparison
standard three-phase
induction motor
(bottom) and optimized
PM engine (top)

The advantages of EC+ technology include the following factors:

• Possibility to select the type of motor used (permanent magnet motor or asynchronous motor).
• The engine control scheme remains unchanged.
• Independence from the manufacturer in the choice of engine components.
• High system efficiency is achieved through the use of high performance components.
• Ability to upgrade existing systems.
• Wide range of motor power ratings.
• Significantly reduced weight and size parameters of the equipment (Fig. 5).

In addition to the advantages listed above, one more feature of the EC+ technology should also be noted. The fact is that ordinary electronically commutated fans cannot provide performance above the nominal, as they have a speed limit. At the same time, fans built according to the EC+ architecture can be overclocked to a speed of rotation of the impeller above the nominal one. In practice, this means the possibility of increasing the air flow above the nominal.

In addition, the operation of EC+ motors can be controlled via BACnet, ModBus and other network protocols.

EC+ technology from an end user perspective

Separately, it should be said about the view of EC + technology from the point of view of end users (as a rule, these are specialists in the design, installation and operation of ventilation systems):

Familiar technology. Many professionals have been using standard Danfoss VLT HVAC Drive series motors for a long time. The configuration of PM motors is almost identical. The user only needs to enter the new motor parameters into the building management system. The principle of controlling the operation of the engine remains unchanged. Thus, the control of engines of various types within the same system is not difficult. It is also possible to replace the standard induction motor with a PM motor.

Manufacturer independent. Users have the flexibility to customize their systems with a choice of standard components from various manufacturers. Optimum system performance. The only way to achieve optimal performance is to use the most efficient components. Users who want to achieve maximum energy savings must not only use efficient components, but also have an efficient system built around these components.

Low maintenance cost. The disadvantage of integrated systems is often the inability to replace individual components. Worn parts (such as bearings) cannot always be replaced without changing the engine itself, which can lead to serious costs. The principle of operation of EC + technology involves the use of standard components that the user can change independently of each other. This minimizes system maintenance costs.

Thus, EC+ technology seems to be very promising in the light of current trends in energy saving and increasing the degree of controllability and controllability of various elements of building engineering subsystems. The versatility of the technology should also play its role - the possibility of its application on previously installed equipment.

Yuri Khomutsky, technical editor of the magazine "CLIMATE WORLD"

The article uses materials from Danfoss technical documentation.

In the modern world, the problem of energy saving has become acute. Therefore, the issues of reducing energy consumption are becoming relevant for air conditioning and ventilation systems, and more and more attention is paid to this issue every year. Increasingly, in the technical specifications for the design of ventilation systems, stringent conditions are set for energy consumption, respectively, experts lay down the most economical equipment. EC motors, which this article is devoted to, are exactly the equipment that allows you to save on electricity, while also increasing the performance of the equipment and its life.

It's no secret that HVAC systems take up about 70% of the energy resources in industrial and large commercial buildings. A new direction in energy saving is the use of so-called EU- engines. The use of these motors is not yet so widespread, but recently both foreign and domestic suppliers offer equipment equipped with EC motors.

What isEU-engine?EU-engine - this is a brushless synchronous motor with built-in electronic control, otherwise it can be called electronically commutated, hence the Latin abbreviation EU- Electronically switched. Fans made on the basis of this motor are called EC fans.

The EC motor is built on the basis of an external rotor, to which permanent magnets are located. The rotor is controlled by a controlled supply of electricity to the stator winding, and depends on the current position of the rotor. The rotor is monitored using Hall sensors, as well as control parameters that are set from external sensors in the form of current or potential signals. The engine has a built-in PID - controller (proportional-integral differential), it allows you to set the speed of the engine's response to a change in the control signal.

How the EC motor works can be described in this way, the control of the magnetic field vector created by the built-in magnets is carried out by changing the direction of the current in the stator winding. The controller calculates what polarity is needed for continuous rotation of the rotor at a given speed.

Another benefit to usingEU-motors can be considered minimal heat generation, while AC motors have a working temperature of up to 75 degrees. Permissible engine operation temperatures are +75 and 20C.

So why useEU- motors justified? Here are the main advantages - compact size, high energy saving rates, smooth and precise control, low noise level, reduced heat generation, almost complete absence of vibration, high aerodynamics and power matched with the impeller, higher motor resource. EC motors have practically no peak starting loads, thanks to the built-in regulator, which provides a smooth increase in amplitude. The starting current usually exceeds the rated current by 5-7 times in AC fans, which entails the need to increase the wiring cross-section and the parameters of the starters.

EC motors have a higher efficiency, reaching 80-90%, since the rotor is external with permanent magnets, as a result of which there are no heat losses, compared with a short-circuited rotor of an asynchronous motor.

A high degree of energy saving is achieved, among other things, by controlling the speed. Energy savings up to 30% compared to three-phase AC motors. In addition, EC motors are less sensitive to power surges due to electronic regulation.

From an operational point of view, the advantages of EC motors are due to the fact that the rotating parts are designed as one dynamically and statically balanced component, the total weight of which is evenly distributed on both support bearings, which significantly affects the service life of the product. A concomitant circumstance is also the minimum vibration and noise during the operation of the EC motor.

What other arguments are needed for using equipment with EC motors?

EC-motors: what, where, why and what for

E. P. Vishnevskiy, Candidate of Technical Science, technical Director, United Elements Group
G. V. Malkov, Product Manager

Specialists today are becoming more oriented on purchasing of energy saving equipment. It is more expensive than traditional, but fully pays back for itself in the process of operation.EC-motors described in the article allow for energy consumption reduction while increasing the equipment performance and time-to-fail.

keywords: EC-motor,EC-fan, energy saving equipment

Description:

Currently, specialists are increasingly focused on the purchase of energy-saving equipment. Compared to the traditional one, it is more expensive, but fully pays for itself during operation. EC motors, to which this article is devoted, allow to reduce energy consumption, while increasing the productivity of the equipment and the period of its uninterrupted operation.

EC motors: what, where, why and why

Energy savings with EC systems in various areas

conclusions

Summarizing all the advantages of systems acquired with EC technology, the main thing can be highlighted: electronically controlled EC fans respond smoothly to changing power output requirements, operate in a particularly economical partial load mode and are insensitive to voltage fluctuations. EC fans provide up to 30% reduction in electrical energy consumption compared to conventional three-phase AC fans.

Literature

1. Vishnevsky E. P. Energy saving in the design of building microclimate systems // Sanitary engineering, Heating, Air conditioning (S. O.K.). - 2010. - No. 1.
2. Vishnevsky E. P., Chepurin G. V. New European standards in the field of HVAC // Plumbing, Heating, Air Conditioning (S. O.K.). - 2010. - No. 2.
3. EC fans in heat pumps // Plumbing, Heating, Air Conditioning (S.O.K.). - 2008. - No. 6.
4. EC fans for vegetable storages and mushroom chambers // Plumbing, Heating, Air Conditioning (S.O.K.). - 2010. - No. 1.
5. Great climate and low energy costs with EC fans in Airius air circulators // Plumbing, Heating, Air Conditioning (S.O.K.). - 2008. - No. 2.
6. The synergy of EC motors and FCUs // Modern Building Services. 2006, August.
7. EC motors for unit coolers // Product Bulletin. October 2007
8. GOST-R 52539-2006. Air purity in medical institutions. General requirements.
9. GOST R ISO 14644-4-2002. Cleanrooms and related controlled environments.

The motor is a DC motor with integrated commutation electronics and permanent magnets in the outer rotor. Such a motor is called Electronically Commutated, or simply an EC motor.

How does the EC motor work?

In the picture we see the engine in the cut. Permanent magnets in the outer rotor and stator windings. Permanent magnets create a magnetic field. With the help of built-in electronics, the direction of flow in the stator winding is changed. Thus, ebmpapst got rid of brushes, which, as you know, are not durable and require regular replacement.

EC motor in section

How does electronics work?

The role of the switch in the ebmpapst EC motor is played by a transistor.

The principle of operation is simple - a low power control signal to the transistor contributes to the passage of a large current through the stator winding. This drives the motor rotor.

If there is no control signal based on the transistor, then there is no current in the winding, there is no acceleration of the rotor at a given time.

Advantages of the EC motor

• The voltage can vary over a wide range. For 1-phase 200-277 V AC, for 3-phase 380-480 V AC. Frequency 50 Hz or 60 Hz.
• The motor has a built-in EMC filter, protection against low voltage in the network, protection against phase failure.
• Built-in protection against overheating of the motor and electronics, the motor simply turns off.
• Built-in protection against blocking of the rotor.
• Low noise level, especially at low speeds.
• Compact design due to external rotor.
• Does not require maintenance throughout the entire service life.
• Long service life as there are no wear parts (brushes).
• High efficiency, up to 92%, minimal energy loss and minimal self-heating.
• Everything is there for control, a frequency converter is not needed, a sine filter is not needed.

EC motor efficiency

Connecting multiple fans in a group

It is possible to combine several EC fans into groups. One fan is the main (master), the rest are slaves (slave). Thus, by controlling the main fan, we control the entire group. This is required when installed on a condenser or in "clean rooms". The control signal 0-10V or 4-20mA should only be applied to the master fan.

Instructions for working with EC-control.

The EC-control program is intended for setting up electronically commutated fans. The program is free.

To receive it, send us a request and we will provide it to you.

(instruction for working with ec-control in Russian 2014)

Video clip EC-technology: