Abstract An electrical switching system of the type which includes a main power switching point, an auxiliary switching point connected in parallel with the main switching point through a secondary circuit which includes a series resistance, and a voltageisolating switching point connected in series with the main switching point. Upon application of a switching-on order, current is caused to flow only through the secondary path containing the series-connected auxiliary switching point and resistance, and also the voltage-isolating switching point which is now closed in order to test the condition of the circuit. If the current flow is abnormally high, the auxiliary switching point is opened and the voltage-isolating switching point is reopened. Thus, there is no current flow through the main power switching point during the test period and this main switching point closes to complete the switching-on order only in the event that the current flow in the circuit is normal.
In a switching system, the combination comprising a main circuit path including first contact means constituting a main switching point, second contact means constituting an auxiliary switching point, a secondary circuit path connecting said auxiliary switching point in parallel with said main switching point through a series-connected resistance, third contact means connected in series with said main switching point in said main circuit path and constituting a voltage isolation switching point, said first and second contact means being closed and said third contact means being open when said system is in a switchedoff condition, means responsive to a switching-on order for temporarily opening said first contact means while said second contact means remains closed followed by closure of said third contact means, and means responsive only to flow of an abnormally high switching-on current through said secondary circuit path subsequent to closure of said third contact means for opening said second contact means and for reopening said third contact means while said first contact means are open.
Claim 2
Dependent Claim
167 words
In a switching system, the combination comprising a main circuit path including first contact means constituting a main switching point, second contact means constituting an auxiliary switching point, a secondary circuit path connecting said auxiliary switching point in parallel with said main switching point through a series-connected resistance, third contact means connected in series with said main switching point in said main circuit path and constituting a voltage isolation switching point, said first and second contact means being closed and said third contact means being open when said system is in a switchedoff condition, means responsive to a switching-on order for temporarily opening said first contact means while said second contact means remains closed followed by closure of said third contact means, and means responsive only to flow of an abnormally high switching-on current through said secondary circuit path subsequent to closure of said third contact means for opening said second contact means and for reopening said third contact means while said first contact means are open.
Claim 3
Dependent Claim
43 words
A switching system as defined in claim 1 and which further includes means for locking said first contact means in an open position in the event of a flow of an abnormally high current through said secondary path subsequent to a switching-on order.
Claim 4
Dependent Claim
50 words
A switching system as defined in claim 1 wherein said means responsive to flow of an abnormally high current through said secondary circuit path for opening said second contact means is constituted by electromagnetic means energized in accordance with the amplitude of the current flow in said secondary circuit path.