Subsynchronous SER Drive

Subsynchronous SER Drive

For those applications with quadratic load (i.e. fans, pumps…) that do not require the hypersynchronous capability, there is a simpler and more cost-effective solution: the Subsynchronous SER Drive (SRD). These drives are used in Wound Rotor Induction Motors (WRIM) as well, and they have the advantage of being able to start the motor from standstill.

Companies looking to reduce the carbon emissions at the same time than reducing the electricity bill of the plant should consider upgrading control regulations of inefficient processes. Typical sources of this inefficiency are: 

  • Variable speed Liquid Resistor Starters (LRS). In the past, variable speed LRS were used as the only economical alternative to variable speed control for large applications. With the current power electronics technology all this energy can be saved and recovered.
  • Regulation of fans/blowers with dampers (i.e. kiln fans, etc). The energy loss caused by dampers compared to the operation of these fans/blowers at variable speed, provides an interesting opportunity of improvement.

Subsynchronous SER Drive offers a perfect opportunity for those applications using slip ring motors (WRIM) to upgrade their processes to state-of-the-art technology without replacing existing motors, saving an important amount of electricity that typically provides payback periods shorter than 1 year with very high return-of-investment (ROI). Detail calculations of process improvement are supported by ElectroDrives during the study phase.

The three main advantages of Subsynchronous SER Drives compared to other classical variable speed systems are: 

  • Top-class energy efficiency. The recovery of the slip energy from the rotor circuit through the SER Drive back to the grid, provides an unbeatable efficiency compared to any other technology.
  • Reliability and Robustness. Our SER Drive is designed with a large safety factor in voltage, current and temperature allowing to have the largest MTBF you can find in the industry. They are also air-cooled and very simple to maintain.
  • Redundancy (with optional/existing LRS). SER Drive is backed up with a starter (LRS or RCD) which allows to bump-less bidirectional transfer to the LRS/RCD in case of any failure preventing motor trips. This provides highest availability of your equipment and avoid unplanned trips in critical applications.