Crane

REPLACEMENT AND PROGRAMMING OF THE FREQUENCY INVERTER 

The first step of the modernization was the dismantling of the original Lenze Motec frequency inverter, which was installed in a decentralized way directly on the electric motor. This motor was located at the beginning of the crane bridge structure and provided the load travel in the X-axis. After removing the inverter, its position was replaced with a metal installation box with outdoor protection rating, which also served as a cover for the motor terminal block. Inside this box, a single-phase rectifier was installed, required for powering the motor’s electromagnetic DC brake, since the new frequency inverter no longer featured a built-in source for brake control. This solution ensured reliable protection of the terminal block, created space for connecting the new power and control cabling, and at the same time enabled full functionality of the motor brake.

The original power cable running from the motor to the switchgear was replaced during the modernization with a new shielded cable providing higher mechanical and electrical durability. The original signal cable, which had been required for the control of the decentralized inverter mounted on the motor, was removed since in the new concept the frequency inverter was located directly inside the switchgear. The new cabling was designed in a modular way – the power cable was terminated with an industrial connector, allowing the crane bridge to be easily disassembled and reassembled during maintenance or service without the need to interfere with the cabling itself.

In the final configuration, only a single combined cable was routed from the switchgear to the motor, containing both the supply conductors for the motor and separate conductors for powering the electromagnetic brake. This solution reduced the number of cables, thereby eliminating potential sources of failure and increasing overall operational reliability.

Another advantage was improved safety, since the new cable runs through the walkable section of the crane bridge structure. By using a single robust cable, the risk of mechanical damage, tripping hazards for operators due to loose wiring, or abrasion of the cables during operation was significantly reduced.

The new frequency inverter was integrated into the existing crane switchgear. Due to space constraints, it could not be mounted on the main mounting plate and was therefore installed on the side wall of the switchgear. Along with the inverter, a new braking resistor was also installed inside the cabinet, which had originally been located near the electric motor. The frequency inverter used was a Lenze i550 with a power rating of 5.5 kW.

The inverter control was implemented exclusively via digital inputs and outputs, without any communication bus. The original concept, in which the control signals were routed directly to the motor with the integrated inverter, was removed along with the associated cabling infrastructure after dismantling. In the new configuration, all control circuits were routed directly within the switchgear and connected to the terminals of the new inverter. The digital inputs of the inverter were configured to control the rotation direction (forward/backward), to activate and deactivate the electromagnetic brake, as well as to process safety signals (emergency stop, limit switches).

The final step of the modernization was the programming of the Lenze i550 frequency inverter. The parameterization was carried out in the Lenze Easy Starter software environment, which enables complete configuration of both motor and application parameters. During programming, it was necessary to correctly define the motor rotation directions and set three fixed speed levels via digital inputs, with the individual levels implemented as predefined frequencies. An important part of the configuration was also the adjustment of acceleration and deceleration times in order to minimize load oscillation during start-up and stopping.

A critical element was the control of the motor’s electromagnetic brake, where the timing of activation and release had to be correctly set in relation to the inverter’s operation to ensure safe and reliable performance. After completing the parameterization, the functionality of movement in both directions at all three speed levels was tested, along with the operation of the electromagnetic brake and the system’s response to emergency stop and limit switches.