In modern drive engi­neering, use is made of elec­tronic control loops to attain maximum perfor­mance and reli­a­bility. But even the best control system is power­less without an effec­tive actu­ator. This is where robust, elec­tron­i­cally commu­tated internal rotor motors (ECI) come into their own. These highly dynamic drive units permit high-speed motion, allow short-term high over­load and operate reli­ably over long periods even without main­te­nance. A new ECI motor with up to 750 W shaft output and a diam­eter of just 80 mm is now setting new stan­dards in terms of power density, dynamics and versa­tility whilst offering stan­dard mechan­ical inter­faces for universal use.

Figure 1: Highly dynamic with over­load capacity and a long main­te­nance-free service life, the ECI 80 with 750 W output power.

Highly special­ized one-off devel­op­ments can achieve top perfor­mance, but at a consid­er­able cost. With series compo­nents, which can be manu­fac­tured more cheaply in large quan­ti­ties, it is however possible to obtain the same perfor­mance levels without high expen­di­ture in the form of a versa­tile modular concept. Indi­vidual modules can be combined to produce drive units tailored to customer spec­i­fi­ca­tions. The specialist manu­fac­turer ebm-papst were there­fore quick to adopt the modular concept for their drive systems. By putting together indi­vidual assem­blies to suit customer require­ments, the company can offer a wide range of drive units “off the peg”. To be able to achieve higher power outputs, the new ECI 80 motor has now been added to the family of drive units along­side the existing ECI 42 and ECI 63 series (Figure 1) to extend the product range, partic­u­larly for appli­ca­tions requiring high power, highly dynamic perfor­mance and a low weight.

Opening up new perspec­tives…

Modern robots, logis­tics, power gener­a­tion, medical engi­neering and tradi­tional sectors such as the wood­working industry all rely on effi­cient, highly compact and powerful drive units. There is an increasing demand for drive units which are even more powerful than the existing modular drives and also offer a compact design. In-depth analysis of the requests made by users revealed that a motor with a shaft output of 750 W would be an ideal addi­tion to the modular range. Based on their expe­ri­ence with smaller drive units, the ebm-papst devel­op­ment engi­neers then worked out a concept for a highly dynamic 3-phase internal rotor motor featuring EC tech­nology. A number of tech­nical hurdles had to be over­come before these require­ments could be satis­fied in reality.

… and putting them into prac­tice

Figure 2: The compact drives with their excep­tion­ally good power/weight ratio are also suit­able for robots. (Photo |fotolia.com/Patrick P. Palej)

The main emphasis was on the highest possible power density, in other words low weight, high power and great effi­ciency. The devel­op­ment process was not made any easier by the some­what conflicting aims of trying to achieve the lowest possible cogging torques and highly dynamic action at the same time. In-house calcu­la­tion and simu­la­tion programs in conjunc­tion with exten­sive testing finally produced the optimum result. The perfor­mance figures and low weight of today’s ECI 80 exactly corre­spond to current and future require­ments. It is thus the lightest motor in its class on the present-day market. A stan­dard­ized system design which enables the motors to be manu­fac­tured on an auto­mated produc­tion line with a very high level of process moni­toring for all oper­a­tions, the perfor­mance char­ac­ter­is­tics and system capa­bility for a wide variety of poten­tial appli­ca­tions all add up to a motor concept which is unri­valed in its class.

With his perfor­mance figures the ECI 80 exactly corre­sponds to current and future require­ments.

For instance it is capable of both precise motion at low speeds almost like a stepper motor and of high-speed switching to dynamic oper­a­tion. The motor is designed and constructed as an internal rotor synchro­nous machine with three-phase perma­nent magnet exci­ta­tion and an eight-pole rotor rotating in a twelve-slot stator. With the robust stator winding there is little copper loss and the manu­fac­turing costs can be opti­mized. The cogging torque can be reduced to a minimum by ideally adjusting the rotor plate contours. The complete absence of beveling in the stator and rotor is also highly advan­ta­geous from a manu­fac­turing point of view. The bar-shaped perma­nent magnets made of neodymium-iron-boron are embedded in the lami­nated rotor core.

Perfor­mance in figures

Figure 3: Reli­a­bility and EMC protec­tion are essen­tial in medical engi­neering, e.g. for high-power oper­ating table adjusters.

The three-phase brush­less internal rotor motor is provided with quiet-running, robust ball bear­ings for main­te­nance-free oper­a­tion. During the life expectancy of 20,000 hours, the drive shaft can with­stand a radial and axial load of up to 28 kg at nominal speed. ebm-papst can supply the motors in versions for 24 and 48 VDC with a nominal speed of 4,000 rpm and a rated torque of up to 1,800 mNm at the motor shaft. The starting torque can be up to 5,600 mNm. With a shaft output of 750 W, the nominal current draw is below 20 A. The peak starting current of the drives with short-term high over­load capacity is up to 100 A. The total weight of the most powerful motor with a length of 136 mm and a diam­eter of 80 mm is around 2.1 kg.

Adapt­able drive solu­tion for a wide range of appli­ca­tions

The modular design means that the drive systems, comprising the motor, elec­tronics, gearbox, brake etc. can be designed and config­ured to meet indi­vidual require­ments. This allows optimum incor­po­ra­tion into many different appli­ca­tions. The stan­dard areas of use for the powerful ECI 80 motors include automa­tion with typical appli­ca­tions such as posi­tioners for wood­working machines and intral­o­gis­tics with driver­less conveyor systems as well as shut­tles and belt drives.

Figure 4: Capturing more solar energy with adjusters such as trackers for solar panels is another talent of the robust, main­te­nance-free ECI 80 motor. (Photo | fotolia.com/idrive)

The compact drives with their excep­tion­ally good power/weight ratio are also employed in the field of robotics (Figure 2). Christleven explains: “The design of the motors makes them suit­able for use in areas with special require­ments such as medical engi­neering, where partic­u­larly high stan­dards have to be met in terms of reli­a­bility and EMC protec­tion. Exam­ples include high-power oper­ating table adjusters (Figure 3) to move every patient to the correct posi­tion, as well as mobile patient lifts for indi­vidual and ergonom­ical bedside care. Despite the amount of power involved, the high level of effi­ciency ensures long battery oper­ating times.” The new energy-effi­cient top performers also make their contri­bu­tion to the energy tran­si­tion process. Adjusters such as trackers for solar panels (Figure 4) constantly guar­antee an ideal setting with respect to the sun, what­ever the weather and over the course of decades.