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Improving effi­ciency with EC motors

Not only do the latest elec­tron­i­cally commu­tated motors (EC motors) consume much less elec­tricity, they are usually consid­er­ably more compact at equal or even higher power output. Their use in house­hold appli­ances provides an example of the resulting bene­fits for machinery and equip­ment. A few scenarios described below show the advan­tages.

When existing drives need to be replaced, the avail­able attach­ment points often need to be taken into account. Drop-in replace­ment, i. e., simply exchanging motors when the rele­vant parts have iden­tical dimen­sions, is then called for. It is quite all right for the shapes and dimen­sions of the motors to vary, but shaft diam­eter and length, vibra­tion absorbers and hole diam­e­ters on mounting brackets should be iden­tical. Since (built-in) house­hold appli­ances are usually manu­fac­tured with stan­dard dimen­sions, smaller drives mean more usable volume. They also facil­i­tate the inte­gra­tion of parts for new conve­nience func­tions.

In addi­tion to these mechan­ical consid­er­a­tions, an increasing number of legal require­ments now needs to be met. In both the EU and the US, in Canada and other coun­tries, there is a host of laws, guide­lines, direc­tives and energy conser­va­tion stan­dards imposing appli­ca­tion-depen­dent minimum require­ments on the energy effi­ciency of appli­ances.

ebm-papst uses flex­ible, elec­tron­i­cally commu­tated DC motors even at low output levels.

In the EU, the Ecode­sign Direc­tive 2009/125/EC provides the neces­sary frame­work for spec­i­fying require­ments for the envi­ron­men­tally compat­ible design of energy-related prod­ucts (ErP), including the trans­parent presen­ta­tion of the energy effi­ciency classes A+++ to G on energy labels affixed to appli­ances. Depending on the appli­ca­tion, even small savings can be impor­tant in enabling a manu­fac­turer to adver­tise higher effi­ciency with a better label.

And what does this mean in prac­tice?

Simple motor designs such as shaded-pole or asyn­chro­nous motors are often no longer able to fulfill modern energy consump­tion and power density require­ments. Motor and fan manu­fac­turers such as ebm-papst Land­shut there­fore use flex­ible, elec­tron­i­cally commu­tated DC motors even at low output levels. In contrast to conven­tional asyn­chro­nous shaded-pole motors, these small synchro­nous motors are highly effi­cient.

Figure 1: Aero­dy­nam­i­cally opti­mized: VHD 0146 stan­dard blower with stan­dard­ized outlet and contact protec­tion inte­grated in the intake.

In some cases, the commu­ta­tion elec­tronics even take over the func­tion­ality of a wide-range voltage input; such motors can be used without modi­fi­ca­tion in almost all of the world’s power networks, making adap­ta­tions due to differ­ences in grid frequency (50 or 60 Hz) unnec­es­sary. Thanks to their inge­nious designs, these compact motors can be inte­grated into a number of appli­ca­tions.

Three example drive appli­ca­tions demon­strate the poten­tial of EC motors: a compact motor for a dual-intake range hood blower; a drive for refrig­er­ated display cases, refrig­er­a­tors, freezers and refrig­er­ator-freezers; and a centrifugal fan for drying appli­ca­tions.

Centrifugal fans for extrac­tion systems

When large volumes of air need to be moved at medium to high pres­sure increases, dual-intake centrifugal fans are ideal. They are used in both house­hold and tech­nical appli­ca­tions, such as range hoods or soldering fume extrac­tors.

Figure 2: The VHD 0146 EC blower for range hoods covers typical air perfor­mance require­ments in the range from 600 to 800 m³/h (free jet), replacing up to three AC blowers.

In addi­tion to improved energy effi­ciency, oper­ating noise needs to be kept as low as possible. Range hood blowers such as the VHD 0146 are supplied as complete units comprising motor, impeller, and fan housing with corre­sponding aero­dy­namic opti­miza­tion of the intake/outlet (Fig. 1 and 2).

With their compact form, EC motors leave more space for the aero­dy­namic design. In addi­tion, their speed and air perfor­mance can be easily controlled with the commu­ta­tion elec­tronics, for example by pulse width modu­la­tion. Depending on the motor model and fan series, addi­tional features such as mois­ture or temper­a­ture sensors can be inte­grated for an auto­matic venti­lation system.

Refrig­er­a­tion appli­ca­tions

The air flow inside modern refrig­er­a­tors and outside at the condenser is opti­mized by fans, which can be used to break up temper­a­ture strat­i­fi­ca­tion or, with directed circu­la­tion of cold air, to create fresh food zones or prevent conden­sa­tion. Air flow routed through the condenser improves heat transfer; heat sinks can be more compact, increasing both the effi­ciency and the capacity of refrig­er­a­tors.

Figure 3: The DE 20 motor is specially opti­mized for refrig­er­a­tors and freezers and is designed for stan­dard speeds of 2,200 or 2,500 rpm in combi­na­tion with a four-blade impeller with a diam­eter of 100 mm.

To make use of the effi­ciency of EC motors in existing appli­ances, the special­ists in Land­shut have devel­oped the DE 20 motor specially for refrig­er­a­tors and freezers. The motor’s shaft length and diam­eter are the same as those of the shaded-pole motors previ­ously used, so the spacing between the impeller and the heat exchanger (evap­o­rator or condenser) can be main­tained. The motor and the elec­tronics are enclosed in a smooth housing, and the unit is connected as before with a two-wire cable. With a height of 40 mm, the housing dimen­sions corre­spond to the most commonly used stan­dard size (Fig. 3).

With elec­tronic commu­ta­tion, the motor speed is decou­pled from the line frequency, so the fan’s size and shape can be chosen according to purely aero­dy­namic consid­er­a­tions and its speed is adjustable. Fans with stan­dard speeds of 2,200 or 2,500 rpm and a four-blade impeller with a diam­eter of 100 mm fit in many refrig­er­a­tors as drop-in replace­ments. In this way, energy consump­tion can be reduced easily when modern­izing product lines.

Time-saving and effi­cient laundry drying

Centrifugal fans are ideal when high air perfor­mance and a signif­i­cant pres­sure increase are needed. They are used in appli­ca­tions such as clothes dryers and washer-dryers. Heat pump systems are often used in such appli­ances for effi­ciency reasons. They heat the air for drying the laundry in the drum. In a cycle, the heat pump extracts the heat and condenses the water from the warm, moist “exhaust air” and uses the recy­cled energy to reheat the now cold and dry “intake air.”

Only minimal heat losses need to be compen­sated, which reduces power consump­tion. However, addi­tional compo­nents such as compres­sors, condensers and evap­o­ra­tors used in heat pumps need space. And the capacity of laundry drums has risen over the years from about 5 kg to as much as 15 kg. Both factors limit the space avail­able for addi­tional compo­nents since the stan­dard outer dimen­sions of house­hold appli­ances stay the same.

Figure 4: With its compact design, the R3G 150 centrifugal fan with EC drive delivers high air perfor­mance even where space is limited.

A new, very compact centrifugal fan is the answer to this trend. With its compact design, the R3G 150 centrifugal fan with EC drive (Fig. 4) can deliver high air perfor­mance even where space is limited. Compared with previous AC solu­tions, it offers better perfor­mance in terms of both pres­sure increase and air flow. Higher air flow at higher pres­sure allows a more compact fan design. The higher motor speed enabled by the use of EC tech­nology allows the use of a smaller, aero­dy­nam­i­cally modi­fied impeller. The minia­tur­ized fan that results can fit in the smallest corner.

Increasing demands on motor energy effi­ciency and the trend toward ever smaller size at ever greater output are being met by devel­opers with customized EC motors. Compact size, speeds inde­pen­dent of the line frequency, and exchange­able plug & play designs make the new drives the ideal choice for savings. Depending on appli­ca­tion, oper­ating mode and model, poten­tial energy savings can be as high as 70%. This enables appli­ance manu­fac­turers to quickly and easily modernize existing house­hold appli­ance product lines, in the best case simply with drop-in replace­ment. 


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