The frequency inverter for servo duties

Written by: Lenze Ltd | Published:

Lenze 8400 TopLine takes on servo applications with inverter costs.

For many years the performance gap between frequency inverters and servo drives has been narrowing. Today the boundaries between them are blurred and difficult to define. Nevertheless servo drives remain more complex, expensive and difficult to apply. Lenze have stepped up to this market requirement for servo performance with inverter attributes by introducing the 8400 TopLine. Their starting point is the modern but established inverter series 8400 StateLine/HighLine. This has kept costs low and reliability high. The new TopLine takes on servo applications by being able to drive synchronous motors and with extended feedback options. The result is more than savings in purchase cost as TopLine brings many more advantages that save time and costs.

The Lenze 8400 range was launched in 2008 with a low-end model called BaseLine suiting applications such as fans and pumps, then two progressively scaled models, the StateLine and HighLine. These suit more complex requirements with open or closed loop control. Power range is from 0.25 up to a newly extended 45kW. The HighLine models are particularly strong for cyclic and positioning applications with a built in controller and the possibility of up to 180 cycles per minute with encoder feedback. Now a new model, the 8400 TopLine extends the range and is targeted at low- to mid- range servo duties. TopLine runs synchronous servo motors and has feedback options for resolvers, HTL, TTL encoders also SSI absolute encoders. It is closely based on the 8400 HighLine and appearance is virtually identical except for feedback plugs and an extra 15mm of depth.

The Holy Grail for most machinery designers is to get more output, i.e. to run at a faster speed, but with lower costs. Running faster will often require servo drives and here the 8400 TopLine can unlock the door to a new area of price and performance. Unit costs are low thanks to most components coming from an inverter design base which is already proven and is volume production. Further cost savings come from the reduction in panel sizes arising from compact dimensions. Integrated features such as filters and brake transistors reduce the external component count and save both installation time and further panel space.

TopLine can be sized to directly match application requirements thanks to 17 power levels from 0.25 to 45kW. This exact matching is the process that Lenze term "Rightsizing". Models are available for 1-phase supply to 2.2kW and 3-phase 400V for all power levels to 45kW. The compact dimensions are illustrated by the footprint of the 5.5kW/13A model which is 270 x 140 mm. Higher powers offer even higher power densities. Within the TopLine dimensions is an integrated RFI filter for category C2 with up to 25m of shielded cable. Also included is brake transistor which allows direct connection to braking resistors when higher moments of inertia need to be stopped. Optionally Safe Torque Off (STO) can be built in a small surcharge and an additional depth of 20mm. This can simplify the circuitry saving component cost and wiring time, and also allows instant restarts after a stop button is pushed, saving cyle times.

A less well known option that also reduces panel sizes is the Lenze 'Cold Plate' technology. All drives need to keep the electronic switching components cool in order to achieve long service life. This is generally achieved by cooling ribs on the back of the drive. However where the inverter is to be mounted onto a substantial metal surface, the cooling from the ribs is no longer necessary. Lenze offer a Cold Plate version of the 8400 inverters which has no ribs and is therefore of a shallower depth. The result is a reduction in required volume of about 20%.

The advantage from TopLine driving synchronous motors compared to asynchronous motors is the reduction in inertia which can be 65% or more. This can make the drive system much more dynamic. Whereas the 8400 HighLine can achieve a respectable 180 cycles per minute, the TopLine with synchronous motors can achieve a remarkable 300 cycles per minute. Overload currents available are 200% for 3 seconds or 150% for 60 seconds. The performance accuracy is dictated by the evaluation of the feedback signal which is done at 100kHz and this can lead to a precision of 0.01mm. It is easy to take advantage of this precision on positioning applications. A point-to-point positioning control is integrated for up to 15 target positions and their associated travel profiles. This can save the need for a separate motion controller.

Customers ordering the 8400 TopLine do not just get a powerful servo drive, they get the 8400 drive system. A CANopen connection is built in at no extra cost and optional plug-in communication modules include high speed real-time PROFINET, EtherCAT and POWERLINK. Pre-configured cables are ready for power and feedback. Free-of-charge L-force Engineer parameterisation software covers all drives in the 8400 series, also the 9400 servo, controllers and I/O. Transferring parameters from drive to drive is made easy with a pluggable memory chip. Settings can be transferred in seconds from chip to chip with a battery powered copier which speeds installation and commissioning. Built-in password protection can give the machine builder security by preventing operators from changing critical parameters.

The new 8400 TopLine is the answer for reduced costs on low- to mid-end servo requirements such as pick & place, storage retrieval units and cycling/positioning. A power range from 0.25 to 45kW includes models for single phase supply up to 2.2kW. The 8400 TopLine drive system presents savings in purchase costs, panel sizes and wiring times. Particularly in complex drive systems, the L-force family makes design, implementation and diagnostics an easier task.

About Lenze Ltd
Established 40 years ago in Bedford, Lenze Ltd now has 60 employees and achieves sales of about £20M in power transmission equipment from the Lenze factories and other quality suppliers. Services to UK customers include application engineering, software writing, training, commissioning and service.

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