DC drives are able to show the full range of their virtues in many areas of application. Which drive system best satisfies the requirements of the user must be decided in each individual case, after all the relevant technical and economic factors have been taken into account.

The advantages of DC drives however, are manifold. Tried and tested in practice and without complicated operating procedures DC drives are characterised by their linear closed-loop performance. The speed of the motors is controlled by altering the armature voltage whereas the torque is proportional to the current and can be kept at a constant level throughout the whole control range (armature control range). The speed control range can also be extended by weakening the excitation current for the field (field-weakening operation), the output in this range remaining constant.

Since only a relatively simple conversion of three-phase current into DC current is necessary, the units are especially compact and easy to handle. Equipped with the latest state of the art in processor technology, the drives can satisfy all and any of the requirements of modern machine and plant engineering. Reliable and user friendly Thanks to the simple relationship between voltage and speed, the control system is very easy to understand and the converter extremely simple to operate. The user can therefore make all the settings needed for highly complex drive tasks just as precisely as simple standard applications.

The development of DC motors in recent years has concentrated on improving the use of the space available and reducing the maintenance effort. With the help of computer-aided methods of calculation, both thermal and magnetic utilisation have been optimised as well. The result is a perfectly co-ordinated system which, in conjunction with improved materials, now allows a brush service life of more than 15,000 operating hours. The bush service life today is approximately the same as the interval between maintenance work on the bearings.

High-quality insulation materials ensure the high thermal safety of the machines, and thus the high level of availability of modern DC drives. Fully digitised converters The fully digitised converters are user-friendly and easy to operate. A keyboard with a display of the drive data directly fitted on the unit enables simple adjustment of the necessary control parameters during operation. Remote parameterisation and remote monitoring/diagnosis are also possible centrally via standard interfaces and a bus system. With the user-specific software, extra functions can be implemented at any time due to the additional options available. Linecommutated thyristor converters make up the core of the power section. They operate with a high level of efficiency but with low forward losses and minimal switching losses. The feed back of power into the supply system with simple means - in the case of reversing operation for example - lowers the consumption of energy and therefore costs as well. The blocking voltage of the thyristor enables use of the converters where there are high supply voltages. This is especially the case with DC technology.