Isolation circuit for arc reduction in a dc circuit

Claim 1

In a direct-current circuit including a D.C. voltage supply having first and second poles, an inductive load having one side connected to said first pole, and make-break switch means having first and second electrical contacts and means for closing said contacts and for opening said contacts; means for isolating said load from said switch contacts comprising: a. triode switch means having first and second power electrodes and a gate electrode, b. means connecting said first power electrode to the other side of said inductive load, c. means connecting said second power electrode to said second pole, d. resistive gating means of predetermined value connected in electrical series with said second pole, said first and second contacts and said gate electrode, e. said resistive gating means impressing a sufficient voltage upon said gate electrode, when said contacts are closed, to bias said triode switch means in conduction with a minimum of current passing through the closed contacts; f. said resistive gating means turning off said triode switch means, when said contacts are open, to shunt the back E.M.F. currents generated in the collapsing inductive load only through said power electrodes to isolate said load from said make-break switch contacts.