Optimizing Precipitator Power Circuits

In a previous ESP Technical Tip about optimizing your precipitator, we explained why troubleshooting should always start inside the box with a look at plates, discharge electrodes and other internal components. Building on this, your next step is to consider electrical components and how they inter-relate to efficiently feed power into the precipitator–or not.

The two main electrical components to consider are Current Limiting Reactors (CLRs) and T/R sets. The CLR is the primary component that shapes electrical waveforms being fed into the precipitator; it does this by opposing rapid changes in current, using an electromotive force. CLRs also limit current during overload (sparking) conditions. The T/R set is a high voltage transformer and rectifier that converts A/C power to D/C and feeds it into the precipitator.

To efficiently get power into the precipitator, both CLRs and T/R sets need to be appropriate sized in relation to one another and to the ESP field. It takes two to tango, a T/R set and a CLR. If these components are mismatched, the precipitator can’t run at peak efficiency.

Ideally, CLRs should be matched with T/R sets in such a way as to provide full primary current at a target conduction angle of between 120 degrees and 150 degrees. For most precipitators, if the conduction angle falls below 100 degrees or so, some losses in collection efficiency will occur. Conversely, conduction angles above 150 degrees have no added benefit.

At many power plants, ESPs were originally built with equally sized (or rated) T/R sets on all the fields. The rating was probably chosen to best suit the outlet collecting fields, since those sections draw the most current. But, this is not an efficient way to distribute power; it creates an immediate power circuit mismatch.

Because of high particulate loading, the inlet fields typically draw 80% less current than the outlet fields. T/R set sizes/ratings should progress from front to back of the ESP, getting increasingly larger.

Matching the size of T/R sets and CLRs to each field’s power demands is key to optimizing the power circuit. Result: improved particulate charging, boosted field strength and enhanced overall ESP collection efficiency.