Optimisation of geared motor drives

Application of the 87 Hz characteristic in secondary settling tanks

Industry
Treatment plants

Sewage treatment plants and secondary settling tanks

Challenge

In the process of selecting geared motors for pumps operating in secondary settling tanks, it was initially assumed that an equivalent of the existing drive would be used, based on data from the nameplate. After detailed analysis, it became clear that such a selection was not enough. The existing drive was precisely matched and each rotation of the gear shaft had a direct impact on pump performance. The selection of a new mechanical system that would provide the same performance parameters proved impossible. For this reason, a decision was made to implement a solution that would allow the drive’s operating parameters to be fine-tuned.

Analysis and approach

It was decided to regulate the drive using a frequency converter, which allowed for precise adjustment of the motor operating parameters. The main challenge was to increase the speed of the motor without losing torque, a typical problem when operating above the rated frequency. Two options were analysed:
Link do przemienników częstotliwości

Operation in the field weakening range – this method involves increasing motor speed, but at the expense of reducing torque.
Operation in the 87 Hz characteristic – this solution allows to maintain the nominal torque at an increased rotational speed.

The first option was discarded because the increase in rotational speed resulted in a decrease in torque, which negatively affected the efficiency of the pump. Ultimately, the 87 Hz characteristic was adopted as the most optimal.

Solution

The use of 87 Hz characteristic allowed for:

Adjustment of engine speed over a wide range while maintaining rated torque.
Precise adjustment of drive operating parameters depending on the load.
Maintaining stable pump performance by dynamically adjusting the speed depending on the current operating conditions.

Thanks to the utilised technology, it has become possible to increase the speed while maintaining full engine power. The use of a frequency converter has enabled even more precise control of the drive’s operating parameters.

Zastosowanie charakterystyki 87 Hz w osadnikach wtórnych

The use of the 87 Hz characteristic brought the following benefits:

Optimisation of operation of pumps in secondary settling tanks, ensuring the required performance parameters.

Flexibility of the solution – the possibility of applying this technique in all drives powered by a frequency converter.

Precise load-dependent control of motor parameters, allowing for efficient use of available power.

Summary

The implementation of the 87 Hz characteristic in drives controlled by a frequency converter has made it possible to achieve high pump efficiency while maintaining stable mechanical performance parameters. This solution offers a wide range of rotational speed regulation, ensuring full control over torque under different load conditions.

The use of this technology can provide an effective solution for applications requiring precise drive control, where traditional mechanical drive selection is not sufficient.

Optimisation of geared motor drives

Challenge

Analysis and approach

Solution

The use of the 87 Hz characteristic brought the following benefits:

Summary

See also

Expert assessment and refurbishment of Flender gear units for a company in the energy sector

Using a Digital Twin in the Modernisation of the Warehouse of a Pharmaceutical Company

Selection of drives for machines at the Waste Disposal Plant