**7. Conclusion**

The application of squirrel cage induction motors supplied from the frequency converters (also known as adjustable speed drive) have become the standard solution for the modern crane drives. However, the standard configuration of the inverter can not be used for some drives primarily due to regenerative operation, which in some cases may be intermittent (long travel and cross travel) and continuous (lowering). The power and torque requirements in details are described and analyzed for such drives. From the aspect of the required power crane drives are often implemented as a multi motor. One of the important issue in this case is load distribution between the motor proportional to the motor power rating which can be resolved by applying the modern converters in one of the master-follower configuration.

This chapter describes the solutions that are commonly used in modern crane drives. In case that it is a casual recuperating the dynamic braking is used. If continious regeneretation occur active front end rectifier capable to returning energy into the supply network is used. The following two case studies are selected. Case study 1 is typical because the AFE is used which in addition of power recovery possibility also serves to supply all the drives on the

**Part 2** 

**Manufacturing Processes** 

**and System Analysis** 

common DC bus. Case study 2 deals with gantry cranes that have a large span. Solutions of two problems that occur in these types of cranes are shown as follows: load distribution between multiple motor and skew problem as a result of a large span.
