“AC2EC” – Replace­ment made easy

The effi­ciency of the fans used is a central issue in venti­lation and air-condi­tioning tech­nology. This is encour­aged not only by the statu­tory basis created with the Energy Conser­va­tion Direc­tive, but also by increased envi­ron­mental and cost aware­ness on the part of users. Against this back­ground, it is no surprise that energy-effi­cient EC tech­nology is increas­ingly being employed in all areas of appli­ca­tion. To offer manu­fac­turers of venti­lation and air-condi­tioning units the option of contin­uing to use conven­tional AC tech­nology or switching to energy-effi­cient EC tech­nology in the future, the instal­la­tion condi­tions for both motor tech­nolo­gies have to be iden­tical. A new gener­a­tion of EC motors is for the first time as compact as existing AC versions and mechan­i­cally full compat­ible. This means that fans can employ either AC or EC tech­nology – without having to modify the venti­lation or air-condi­tioning unit.

So-called “asyn­chro­nous motors” are frequently employed today to drive fans in venti­lation and air-condi­tioning units. These AC motors are compact and simple assem­blies as they are fed directly from the A/C or three-phase current supply. Neither mechan­ical collec­tors nor elec­tronics are needed to power the rotor. They are robust and reli­able. However, EC motors achieve a much higher degree of effi­ciency than AC motors, and this will be neces­sary in the near future with an eye on the require­ments of the Energy Conser­va­tion Direc­tive.

The neces­sary elec­tronics for EC motors have to be accom­mo­dated in a limited space.

But that need not be a problem for the manu­fac­turers of venti­lation and air-condi­tioning units. The motors and fan specialist ebm-papst Mulfingen has devel­oped a new gener­a­tion of EC motors featuring inte­grated commu­ta­tion and drive elec­tronics, and which are just as compact as conven­tional AC motors. On both axial and centrifugal fans, the orig­inal AC motors can now be simply exchanged for a new EC design. The excep­tion­ally high effi­ciency of EC motors – up to 90% – can be enjoyed without having to make design modi­fi­ca­tions to the customer’s equip­ment. Oper­ating costs are cut and substan­tially less CO2 is gener­ated from the very first hour of oper­a­tion, reducing the impact on the envi­ron­ment. At the same time, the drives impress with their quiet running, which is espe­cially bene­fi­cial for equip­ment used in domestic appli­ca­tions. The key to this is an espe­cially low-noise commu­ta­tion which is precisely adjusted to the three core elec­tron­i­cally commu­tated motor.

Iden­tical input and output dimen­sions

EC motors are, by way of their prin­ciple, synchro­nous motors actu­ated by perma­nent magnets. The magnetic rotor synchro­nously follows an elec­tron­i­cally gener­ated rotating field. This allows any random oper­ating speeds to be realised, regard­less of the power frequency used. The devel­op­ment repre­sented a great tech­nical chal­lenge to accom­mo­date the elec­tronics needed by EC motors in the limited space avail­able. Apart from the minia­tur­i­sa­tion and opti­mi­sa­tion of the elec­tronics, mechan­ical compat­i­bility was also a neces­sity. This includes, for example, the same mounting flange design as that employed on AC motors and the complete struc­tural shape of the motor had to be modi­fied.

The mounting area of the new EC motor (left) and that of a conven­tional AC motor (right) are iden­tical.

Good heat dissi­pa­tion and protec­tion rating

The new compact EC motors are based on the proven external rotor prin­ciple in which the rotor turns around the internal stator. The stator core is coated in ther­mo­plastic, which has several different bene­fits in prac­tical appli­ca­tion. Firstly, the high-quality plastic mate­rial provides for good elec­trical insu­la­tion. And secondly, the ball-bearing mounting can be inte­grated. Panel thick­nesses and sepa­ra­tions can be varied according to design. Toler­ances in the core pack, for example, can be compen­sated for in this way. After this, the complete winding of the subassembly is coated with duro­plastic. The single-piece rotor, which turns around the stator, has been aero­dy­nam­i­cally opti­mised. Air intakes in the rotor provide for perfect heat dissi­pa­tion for the stator. In conjunc­tion with the coated stator, a high IP protec­tion rating (IP54) is guar­an­teed for the motors.

The sealing of the elec­tronics also plays an impor­tant role here. Instead of the solu­tions that used to be common, featuring a flange and various O-rings, the elec­tronics case has been given an elastic sealing compo­nent. That guar­an­tees long-term protec­tion for the elec­tronics. The complete motor is robust, insen­si­tive to shock and impressed with its reli­a­bility and long service life.

Sustain­able design and modular system

When designing the new EC motors, great value was attached to sustain­ability and to resource-conserving manu­fac­turing. There are several details that contribute to this. The single-piece rotor with pressed-in shaft reduced the number of manu­fac­turing steps. Multi­func­tion compo­nents mean fewer indi­vidual parts are needed. The heat dissi­pa­tion concept and a compa­rably compact package length also help to reduce the amount of mate­rial used. Less mate­rial input means less energy consumed during produc­tion.

Coated stator, rotor and compact elec­tronics

The new EC motors are currently offered in size 55 with input capacity up to 170 W. Another expan­sion of the series is planned. The modular concept results in a modular system that permits many different vari­ants. This way, for example, a smaller motor can be equipped with more powerful elec­tronics. This makes sense if more output is required with the same torque. EC motors are avail­able as stan­dard with two speed stages. As an option, a freely adjustable speed control with a 0-10 volt control voltage is possible, e.g. for fan oper­a­tion that is precisely adapted to indi­vidual require­ments. In conjunc­tion with the aero­dy­nam­i­cally opti­mised HyBlade® blades or RadiCal impeller, these fans, with Green­Tech EC tech­nology, repre­sent an energy-effi­cient unit in venti­lation and air-condi­tioning tech­nology. It is there­fore possible to make an straight­for­ward mechan­ical replace­ment of existing fans without having to modify the customer’s unit.