German plant construction makes its living from a high level of innovation and good quality products. These factors contribute to its good reputation and justify reasonable prices. However, innovation demands improvement without a drop in standards. Innovation can only lead to success if the components are also able to keep up to speed. Along with the improved Movidrive B drive inverter, Sew-Eurodrive offers an additional component that makes it possible for the system to be a success.
For five years, the Movidrive application inverter has demonstrated the recipe for success in several hundred thousand installations: a unit series uses the same operation, functionality and connection to drive asynchronous geared motors, asynchronous motors with an encoder system, or highly dynamic synchronous servo motors. The application inverter and the extensive modular gear unit system from Sew-Eurodrive became one system. Today, this complete solution is in demand. Interfaces represent a high risk, especially in areas where the time between the task assignment and start-up is getting shorter and shorter. If the motor and application inverter come from one source as a drive solution, interfaces become essential links. The control unit considers the drive as a mere slave, without worrying about the motion sequence.
However, this requires a high degree of functionality from the application inverter, while at the same time, it must be simple and intuitive to operate. In cases where the tried and tested features of Movidrive are already implemented, Movidrive B offers a compatible, simple changeover to easier operation and yet more functions. The speed of the integrated IPOSplus positioning and sequence control system has been increased 10-fold and it uses the pre-programmed and tested software application modules to carry out tasks such as table positioning, bus positioning, rotary table positioning controlled by incremental or absolute encoders, winding, flying saws, or vertical movements. The position measurements can be taken at many different places. The easiest method is to use the encoder fitted on the motor. This can be a sin/cos, TTL, resolver, Hiperface or SSI encoder. If an encoder is not used, simple sensors with low resolution can determine the position of the motor. In systems where there is no positive connection between the system movement and the speed of the motor because, for example, there can be a slip between the gears and rails or between v-belts and the belt pulleys, a synchronous encoder is used. Movidrive B can position to the precise increment using the motor encoder or the synchronous encoder as a reference, without the programming being changed.
Case study
A high-bay warehouse is to be operated automatically using a storage/retrieval system. Since the warehouse volume is high and productivity is only average, a storage/retrieval system with cornering ability is used. It can switch between the rows of shelves when required. The drive technology is accomplished easily with Movidrive B.
The warehouse management computer transfers the target positions for the drive unit for vertical movement and the travel drive to the application inverter via the PLC and bus system. The position is determined using an absolute measuring system mounted on the track and is evaluated directly in Movidrive B. If there is a curve in the track between the starting and target positions, the inverter switches the vehicle to curve mode to avoid the toppling effect when cornering. To do so, the speed of the front and rear wheels are controlled so that the centre of mass runs through the curve with minimum transverse acceleration. The PLC only has to communicate the start and end of the curve to the application inverter. Movidrive B sorts out everything else itself.
For vehicles with masts taller than 25 m, the inherent instability of the mast increases in particular when the load is at the top end of the mast when the vehicle starts and stops. Movidrive B uses adjustable jerk limitation to prevent such instability. This principle was tested in vehicles with masts 30 m high in a warehouse with 12 vehicles. The pre-programmed software application modules use clearly-defined interfaces to the PLC to allow a quick start-up without the control system manufacturer having to worry about the programming of the application inverter. The assignment of process data for fieldbus communication is preset just as for the drive control; the data only has to be transferred at start-up.
Integrated memory card
Problems most often occur when you are least expecting them. A defect can also occur with inverters. This is no problem if there is a trained technician on hand to exchange the unit. On the other hand, what happens if your customer does not have 24-hour on-site support from electricians trained in engineering technology? This problem no longer exists for Movidrive B implementations. Each application inverter has a pluggable memory card as standard, which automatically contains the current data record. If a unit has to be replaced, this can be done quickly and safely without specially-trained staff. Simply exchange the hardware, replace the memory card, and the system is ready for operation.
Change of location
In automobile manufacturing plants, the production systems are in use 24 hours a day. Being able to exchange units quickly using the pluggable memory card is also invaluable in saving time in this industry. Downtimes costing up to 4000 Euros a minute are evidence of this. In automobile production in particular, great demands are placed on individual installations.
Simple transition belts need to be driven using geared motors at a reasonable price. Right next to them, a positioning drive turns a car body around its longitudinal axis. This enables assembly work on the underside of the vehicle. For personnel dealing with maintenance and technical servicing, reducing the number of unit variants used is essential. A new family means more spare parts and more training for personnel. In this case, Movidrive B can fulfil all drive engineering requirements with one unit equipped with option cards. Whether a simple speed control or highly-dynamic positioning is required, Movidrive B offers the choice.
Wherever engineers are working on the vehicle, the machinery directive stipulates that persons must be protected from dangerous movements. This can either be achieved constructively through very slow movements, although the short cycle times usually do not allow this, or the motors are isolated from their electrical power source and are at a standstill while people are in the area. This method is often used today, but requires the switching of live contacts.
Even high-quality contactors can only tolerate this for a limited period before wearing and requiring maintenance. With Movidrive B, the application inverter can be used as a safety switch without a circuit breaker. The connections required to fulfil the requirements of EN954-1, category 3 are available in the standard unit. This guarantees safe protection against automatic restart. Removing the circuit breaker offers much more flexibility in system reconstruction or extension, which leads to savings in terms of the components.
Rapid start-up with electronic nameplate
When drives from Sew-Eurodrive are equipped with the Hiperface encoder system, the data of the motor nameplate is available on an electronic data medium in the motor(encoder). Once the motor and the encoder are connected to Movidrive B, the application inverter reads the data automatically during start-up and performs the start-up procedure virtually on its own. This ensures a fast and successful start-up. The electronic nameplate also offers the system operator the option of saving data, such as the spare part numbers or motor name, in the motor.
In comparison to the tried and tested concept of the Movidrive series, Movidrive B demonstrates clear improvements in functionality and performance without affecting the compatibility with the implemented installations. There is also the flexibility of different fieldbus system options: Profibus DPV1, Interbus, Interbus LWL and DeviceNet, offering a connection to all the common fieldbus systems. The system bus available in the basic unit can be switched to CANopen, which offers an inexpensive connection to control units. The units up to 1,5 kW have an overload capacity of 200% and are, therefore, particularly suitable for use in dynamic applications.
For more information contact Ute Bormann, Sew-Eurodrive Empowered, 011 248 7000, [email protected], www.sew.co.za
| Tel: | +27 11 248 7000 |
| Email: | [email protected] |
| www: | www.sew-eurodrive.co.za |
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