Primarily, understanding the selection codes of the capacitor switching contactors; to start with is the range name, HDC19s, which is followed by the numerical denoting the frame current varying from 25A to 175A. Next to the sequence, we have the list of auxiliary contacts based on the number of NO and NC contacts.
Contactors are specially designed by contactor manufacturers for operating capacitors and in particular for assembling automatically controlled capacitor banks. These contactors have auxiliary poles combined in series with preload resistors that will limit the inrush current during activation. Go back to capacitors installation options ↑
Application The A...and AF...contactors are suited for capacitor bank switching for the peak current and power values in the table below. The capacitors must be discharged (maximum residual voltage at terminals < 50 V)before being re-energized when the contactors are making.
Contactor versions according to the value of the inrush current peak and the power of the capacitor banks: UA..RA contactors for capacitor switching (UA16..RA to UA110..RA) with insertion of damping resistors for 12.5 up to 80 kvar. The insertion of damping resistors protects the contactor and the capacitor from the highest inrush currents.
The use of standard A 9 ... A 110 3-pole contactors is then possible on multi-step capacitor bank. The capacitors must be discharged (maximum residual voltage at terminals < 50 V)before being re-energized when the contactors are making. In these conditions, electrical durability of contactors is larger than 100 000 operating cycles. Selection Table
There are two basic types of capacitor installations: This application note discusses the stresses and demands on contactors and how to apply Eaton’s contactors in each application. Most loads in modern electrical distribution systems are inductive. Examples include motors, transformers, gaseous tube lighting ballasts, and induction furnaces.