CONTACTORS TYPE CN

CONTACTORS FOR CAPACITORS TYPE CN UP TO 3000V 50-250Hz

The switching of the usual three-phase power factor correction capacitors for motor or lines, is normally exploited by the standard type N contactors in the version with poles type V or S for voltage up to 1000V. Special care must be taken for switching the capacitors (single-phase) used for power factor correction and current balancing of induction furnaces where high frequency of operation and remarkable presence of harmonics is expected.

The contactors CN are properly designed to withstand the increased thermal stresses due to harmonics existing in the circuits feeding the capacitors, and to withstand for a great number of operations the highest overcurrents that may occur when connecting a capacitor.

According to the figured diagram (fig.1), for limiting the above mentioned transient current peaks, the contactor, where provided in the plant, connects the capacitor through a proper limiting resistor, which, after a very short delay, is by-passed by the main pole that connects the capacitor directly to the line.

Moreover the contactor, when opening, can connect the capacitor across a discharge resistor by a proper contact. The above metioned resistances, that on request can be supplied with the contactor, must be carefully designed according to the performances of the contactor itself and in function of the number of operations per hour required. For voltages up to 500V the contactors are fitted with poles without magnetic blowers or arc-chutes. For voltages over 500V the arcing poles are always of the magnetic blowed type with arc-chutes. Moreover, for voltages over 1000V, two or more arcing poles connected in series are provided.

TYPE Rated Operational Current [A] Making current [A] Max N° of oper./ hour 50Hz 100Hz 150Hz 250Hz CN 85 70 65 60 42 3000 150 CN 125 100 90 85 60 3700 150 CN 190 150 135 125 95 4500 150 CN 270 200 180 170 135 8000 100 CN 350 250 225 210 175 9000 100 CN 550 400 360 340 275 10000 100 CN 650 460 410 390 325 13000 100 CN 800 560 500 480 400 16000 60 CN 1000 700 630 600 500 20000 60 CN 1250 900 800 750 650 30000 60

I = arcing pole C = main pole S = discharge resistance connecting contact RI = limiting resistance RS = discharge resistance For reactive power higher than 0.5 KVAR, a discharge resistor must be always provided.