The function of the RC network is to:

(1) Keep the voltage across the contacts below 300 volts. C> (IL/300)2L

(2) Keep the rate of voltage change below 1V/µs. C> IL x 10-6

(3) Keep the current below that described in Table 1.

Capacitors will restrict an instantaneous change in voltage. A capacitor , therefore is useful to counter the

destructive voltages generated at the switch contacts. When the contacts are closed, the capacitor is out of the

circuit. As the contacts are opened any change in voltage is restricted by the capacitor if its value is large enough

to restrict the voltage change to less than 1 V/µs.

A capacitor alone is not an ideal solution. When the contacts are open, the capacitor charges up to the supply

voltage. As the contact is "made", an inrush of current results limited only by a residual resistance and damage

may still result. For this reason, a resistor is configured in series with the capacitor . The higher the resistance

value the smaller the inrush current and the less effective is the capacitor . The voltage across the contacts when

In this case, the maximum resistance of the network (RN) will be equal to the load resistance (RL).

necessary for "Arc Discharges" to be sustained. Contact material also plays a role in sustained "Arc Discharges".

(see Table 1)

MATERIAL MIN. (VA)

Vsource

RL

CN

RN

The circuit to be used is dependent upon particular situations. Either circuit may be enough protection for

µµ

(SOLID COPPERWELD)