Increase system energy efficiency with motor and drive tools

Lenze L-Force Drive Solution Designer (DSD) software design tools, L-force MF ac motors, and the energy-saving VFCeco (Voltage Frequency Control economic) feature in Lenze 8400 inverter drives can reduce energy use and pollution, conserve resources, and lower energy costs without sacrificing productivity.


The Lenze L-Force Drive Solution Designer (DSD) is a powerful set of engineering and configuration tools to help machine engineers set the right course in the design and development phase of motion systems. This new process tool from Lenze helps design engineers select the right drives and motors for optimal machine performance. DSD software enables the exact determination of the process variables and evaluation of the components and their optimum coordination. DSD sizes components based on user-entered machine torque, time, and motion profiles, and generates data specifying where and when and by which means efficient savings can be achieved. The patented Energy Performance Certificate presents the energy consumption of the main drivetrain components calculated by differentiated loss models.

Lenze's Drive Solution Designer and Existing software requires recalculations to compare scenarios. DSD works within a concise and comprehensible graph format clearly showing usage by each component, with a comparative analysis and payback for multiple design scenarios. DSD streamlines the design and sizing process and converts the drive energy savings into kilowatts used, fuel cost, and wasted CO2. DSD provides reliable data by quickly calculating solution variants on the basis of mechanical performance figures. These values are then used to determine the energy costs and CO2 emissions. By comparing solutions, the user can identify the optimum combination of components and the best motion sequence for the drive task. Optimized mechanics and reduced inertias and frictions fundamentally reduce the power requirement to be met by the drive.

Efficient motors

The most widely used class IE1 motors have been phased out and prohibited in some new installations. DSD is a particularly timely tool as machine markets transition to higher efficiency motors. Lenze developed the compact MF series of motors to help design engineers avoid increases in frame sizes and thus complex design adaptations for the migration to Class IE2 ac motors. New to the market, the MF series is designed for open and closed loop controlled operation with frequency inverters. The L-force MF ac motors are developed for a higher nominal speed than conventional 4-pole motors.

Due to its features, the MF motor aligns perfectly with the machine concept. Bridging the gap between conventional servo motors and high-efficiency IE2 Class ac motors, the new L-force MF three-phase ac motors have nominal frequency of 120 Hz with a speed-setting range of 1-24. The MF motor incorporates high ratio gearboxes to achieve higher output speeds of up to 3,500 rpm. With efficiency of 94% to 98%, the right-angle and axial gearboxes ensure almost loss-free energy conversion. Low inertia translates into less energy consumption during speed changes. During rated operation, MF three-phase motors surpass the minimum efficiency of Class IE2 motors but are unaffected by IEC 60034-30. MF can be specified up to two sizes smaller than IE2 motors of equivalent power. Another major plus of the MF motor is its multifunction capability. Applications that may have required multiple conventional motors (of varying frame sizes and power ranges) can now be satisfied with only one MF motor, thereby reducing costly motor inventory.

Lenze L-Force MF ac motors offer an economical solution to close the large performance gap between conventional ac motors and servo motors. Courtesy: Lenze AmericasVariable frequency drive, frequency inverter

Using a frequency inverter to automatically adjust motor voltage produces better efficiency in partial load operations with standard three-phase ac motors. Normally, in partial load operation, three-phase ac motors are still supplied with a greater magnetizing current than actually required by the operating conditions. Additional energy savings can be yielded in combination with high-efficiency gearboxes and inverter drives with energy-saving VFCeco (Voltage Frequency Control economic).

Built in to the Lenze 8400 inverter drives, this energy-saving feature makes it possible to reduce energy consumption by up to 30%. Designed for centralized and decentralized frequency inverters, VFCeco senses load and torque, then adapts to partial loads by automatically reducing the magnetizing current of the motor to the actual requirement. VFCeco can be temporarily disabled for manual control or full load operation.

In the case of load changes (n-settling time < 1sec, for VFC < 0.5sec), VFCeco mode delivers better dynamic performance than other products on the market. In applications with long, extreme partial load phases, a voltage reduction enables the reduction of the average required power. That makes VFCeco particularly practical in applications with great partial load operation, low requirements with regard to the dynamic performance, and infrequent load changes, as commonly found in material handling roller conveyors, conveying belts, pumps, and fans.

Possibilities for increasing energy efficiency can be calculated and compared in DSD yielding a design template for an energy-efficient complete machine.

For more advice and two text tables, see: Adaptive tools, engineering can reduce drive system energy consumption.

- Mariusz Jamroz is senior OEM commercial engineer, Lenze Americas; edited by Mark T. Hoske, content manager CFE Media, Control Engineering, Plant Engineering, and Consulting-Specifying Engineer, 

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