Single-speed motors waste energy in many applications. This may be acceptable where they only run for a short period every day. However, the operating costs should generally be compared to those of a variable-speed solution which will reduce energy consumption, thereby paying off in the short to medium term. More and more often, the most efficient solution turns out to be one with decentralized electronics that are mounted directly on the motor or on a nearby wall. Especially when used in large facilities, such integrated units have the lowest TCO. In order to be able to configure the right drive system for any application, plant designers and engineers require a comprehensive range of drive electronics with graded functions and modular enhancement options.
In recent years, there has been a marked trend towards distributed drive intelligence. Variable-speed pump drives, e.g., replace mains-powered motors that rely on throttles and valves for pressure and flow control. They provide a degree of precision that conventional setups could never reach while at the same time improving the efficiency rating immensely. Instead of letting the motor work full speed against throttles and valve flaps, a frequency inverter can adjust the motor speed almost from zero up to the motor's nominal speed. This way, energy consumption is dynamically adapted to the current performance requirements. In addition to energy savings, the lower noise pollution through decreased speed is another noteworthy advantage.
Lean without a control cabinet
The installation and maintenance of decentralized power electronics require much less time and economic effort than control cabinet setups. Costly shielded motor cables, which otherwise need to bridge wide distances from a cabinet to the individual drive, are not required at all (for integrated units) or very short (if the inverter is mounted in close proximity to the motor). Smaller control cabinets can be used, possibly without cooling, or they can even become entirely unnecessary, saving much space in facilities with many drives.
Full functional range
In some cases, machine-integrated geared motor and inverter units reach the functional level of costly servo solutions. The retrofit of the new generation of palletizers by a Dutch manufacturer is a case in point: servo technology was replaced by integrated drives which NORD DRIVESYSTEMS, as a full-range supplier, custom-tailored based on all in-house manufactured components: gearboxes, energy-efficient motors, and SK 200E frequency inverters. The SK 200E series covers an outstanding performance range up to 22 kW and includes a number of specialized units for various applications, each integrating positioning functions. Models for lifting, hoisting, or safety-oriented applications bring along additional integrated features such as the STO and SS1 safety functions for requirements up to SIL3.
Electronics units for simple drive tasks
Building on the example of the successful top-of-the-range SK 200E line, NORD DRIVESYSTEMS has expanded its variable-speed drive program, adding new electronics units for motor mounting with a graded performance and functional range. A new universal motor starter with extensive protection functions economically implements soft start and reversing operation for motor outputs from 0.25 to 7.5 kW. A new frequency inverter with field-oriented vector control for motor outputs from 0.25 to 2.2 kW concentrates on core functions and is thereby especially budget-friendly.
Advanced efficiency functions
SK 180E variable-speed drives enable lean drive concepts. Strictly limited to simple speed control and efficiency functions, the SK 180E from NORD is nevertheless a fully adequate solution for many drive tasks. The drives have typical overload reserves of 150% for 60 seconds and briefly even up to 200%. Moreover, there is a feasible low-cost procedure that allows users to tap motor reserves and use smaller models: motors can be operated at up to double the mains frequency. Such a speed increase above the nominal speed typically involves a decrease of the output torque - a reservation that NORD effectively counters with 87 Hz operation: a motor with 230 V star-delta wiring is matched with a 3~400V frequency inverter with a performance rating two sizes higher than the motor's. Consequently, the motor supplies its full rated torque up to 1.7 times the mains frequency, increasing drive efficiency by up to 5%. Additional 30% energy savings are possible due to an automatic efficiency function that is a standard feature of all NORD inverters. This function detects partial load and automatically adapts the magnetic flux level.
All that is necessary
SK 180E inverters feature two analog inputs for connecting, e.g., temperature, pressure, or flow control sensors. Integrated process and PI controller functions enable the fully automated control of process variables and compensation of disturbances. Therefore, they are ideally suited for pump and fan applications. On the other hand, they also provide an excellent means for implementing distributed logistics systems. Drives can be networked for synchronous operation via the integrated system bus. Ethernet interface modules enable centralized control via an external PLC. For use in mobile pumps, shredders, or mixers, SK 180E drives are even available with a conventional mains plug.
Universal motor starter
In simple switching applications without speed control, the new SK 135E starter enables the adjustment of ramps and starting torque. The electronic, wear-free switch integrates motor overload protection through PTC thermistor monitoring, mains and motor phase failure monitoring, I²t monitoring, and magnetizing current monitoring. The soft start function prevents shocks during start-up and braking, thereby reducing mechanical stress. A voltage boost can be programmed for applications requiring high break-away torques. For reversing operation, various braking modes are available. The compact starter replaces motor circuit breakers, reversing contactors, and brake rectifiers, thus rendering entire control cabinets unnecessary in large facilities. As PTC thermistor connection cables and brake control cables are not required either, installation becomes generally more cost-effective, space-saving, and faster.
Quick and easy
All NORD drives are mutually compatible and can therefore be combined in plants where different levels of drive intelligence are required. For instance, the SK 135E motor starter can provide for soft start and reversing operation at single-speed conveyors, alongside SK 180E variable-speed drives at horizontal conveyors without high positioning or safety requirements, while SK 200E drives carry out all positioning and lifting tasks. The operator benefits from the single simple and versatile operation concept for NORD's entire electronics program: all major parameters can be programmed directly on the device via potentiometers and DIP switches. Advanced configuration and diagnosis is possible by means of parameter boxes or via computer using the free-of-charge NORD CON software. Multiple-drive facilities are commissioned quickly and easily, since parameters can be exported to other devices using the internal system bus or Ethernet interfaces. A full-range manufacturer of mechanical, electrical, and electronic drive technology, NORD supplies complete drive units (consisting of a gearbox, a motor with the requested or optimal energy efficiency rating, and drive electronics) wired and fully operational, if required. If customers opt for plug connectors, installation is a matter of seconds.
By Jörg Niermann, Marketing Director at NORD DRIVESYSTEMS