Optimization of Energy Costs through Recovery
One of the primary tasks of variable frequency drives is the smooth start of mechanisms and the maintenance of the necessary speed of their movement. However, there are many installations that require not only this but also the deceleration and braking of mechanical elements. Such devices include elevators, winding machines, centrifuges, escalators, and so on.
Generator Action of the Electric Motor
In deceleration and stop mode, the electric motor operates as an AC generator, converting the mechanical energy of the moving mechanism into electrical energy. Typically, this energy is dissipated on a powerful braking resistor, leading to significant losses of electrical energy and the release of heat. This requires enhanced heat dissipation, for example, by increasing the fan power or adding radiators.
However, today devices have been developed that allow the energy generated during braking to be returned back to the electrical grid or to neighboring consumers.
Advantages of Recovery Systems
The main advantage of such systems is the reduction of the amount of heat released, which means less stringent requirements for heat dissipation. This also reduces the risks of overheating components of technological installations, which can lead to emergency situations.
Manufacturers of frequency converters offer models equipped with the recovery function (from the Latin "recuperatio" – "to regain"). Such converters provide significant savings in energy consumption.
Design of Recovery Modules
Structurally, the recovery module connects to the DC link and the power supply network. Sometimes it is implemented as a separate unit. The recovery module usually contains special filters that clean the generated voltage from unwanted harmonics.
Advantages of Using Recovery Modules
Incorporating a recovery module into a frequency converter provides the following advantages:
- reduction in electricity consumption (savings can reach up to 30-35% for some installations);
- decrease in the risk of overheating of the power electrical scheme components;
- more efficient use of workspace, as the need for additional units disappears.
Examples of Frequency Converters with Recovery
Here are some models of frequency converters with built-in recuperators:
- FR-A 741 from Mitsubishi Electric;
- SINAMICS G120 from Siemens;
- VFXR from Emotron and others.
Energy Savings and Payback Periods
In the context of constant price increases for energy carriers and electricity, the use of drives with recovery support helps significantly reduce the payback period of the frequency converter.