Arcless tap- or source-switching apparatus using series-connected semiconductors

Claim 2

Electric power switching apparatus comprising: input circuit means; output circuit means; first mechanical switching means having a pair of metallic contacts, one of which is coupled to said input circuit means and both of which are subject to arcing, erosion, deterioration and the like if said contacts are initially engaged to couple said input and output circuit and if said contacts are initially disengaged to decouple said input and output circuit means; second mechanical switching means, also having a pair of metallic contacts, serially coupled between the other of said pair of first mechanical switching means metallic contacts and said output circuit means; semiconductor switching means coupled in parallel across said second meachanical switching means; and timing control means for closing said semiconductor switching means after closing of said first mechanical switching means by said control means and prior to closing of said second mechanical switching means by said control means to thereby effect current initiation between said input and output circuit means through said semiconductor switching means and for opening said semiconductor switching means after opening of said second mechanical switching means by said control means and prior to opening of said first mechanical switching means by said control means to thereby effect current interruption between said input and output circuits means across said semiconductor switching means; whereby said arcing, erosion, deterioration and the like is substantially lessened.

Claim 3

Electric power switching apparatus as defined in claim 1, wherein said timing control means is included for opening said semiconductor switching means after closing of said second mechanical switching means by said control means and prior to opening of said first mechanical switching means by said control means.

Claim 4

Electric power switching apparatus as defined in claim 1, wherein said timing control means includes a source of control signals for said semiconductor switching means and mechanical linkage means operative to open and close said first and second mechanical switching means and to condition the application of control signals to said semiconductor switching means, all in a predetermined time sequence.

Claim 5

Electric power switching apparatus as defined in claim 1, wherein said input circuit means comprises a source of direct current, wherein said semiconductor switching means includes one of a group consisting of a transistor, a silicon-controlled rectifier, a triac and similar conductivity controllable semiconductor devices and wherein said timing control means is operative to close said switching means by coupling appropriate signals to a control electrode of the one of the semiconductor devices included.

Claim 6

Electric power switching apparatus as defined in claim 1, wherein said input circuit means comprises a source of alternating current, wherein said semiconductor switching means includes at least one of a group consisting of a transistor, a silicon-controlled rectifier, a triac and similar conductivity controllable semiconductor device and wherein said timing control means is operative to close said switching means by coupling appropriate signals to a control electrode of each of the semiconductor devices included to condition said devices to conduct for both positive and negative cycles of an alternating current waveform.

Claim 7

Electric power switching apparatus as defined in claim 1, wherein said input circuit means consists of one of an electric power generating source and a terminal at which electric power is provided and wherein said output circuit means includes a load therefor.

Claim 8

The combination comprising: a plurality of taps at which electric power is provided; a load; first mechanical switching means having a contact arm connected to one of the plurality of said taps and having a pair of metallic contacts, one of which is coupled to said contact arm and both of which are subject to arcing, erosion, deterioration and the like if said contacts are initially engaged to couple said taps and said load means and if said contacts are initially disengaged to decouple said taps and said load; second mechanical switching means, also having a pair of metallic contacts, serially coupled between the other of said pair of first mechanical switching means metallic contacts an said load; semiconductor switching means coupled in parallel across said second mechanical switching means; and timing control means for closing said semiconductor switching means afTer closing of said first mechanical switching means by said control means and prior to closing of said second mechanical switching means by said control means to thereby effect current initiation between said taps and said load through said semiconductor switching means and for opening said semiconductor switching means after opening of said second mechanical switching means by said control means and prior to opening of said first mechanical switching means by said control means to thereby effect current interruption between said taps and said load across said semiconductor switching means; whereby said arcing, erosion, deterioration and the like is substantially lessened.

Claim 9

The combination comprising: a plurality of taps at which electric power is provided; a load; first mechanical switching means having a contact arm connected to one of the plurality of said taps and having a pair of metallic contacts, one of which is coupled to said contact arm and both of which are subject to arcing, erosion, deterioration and the like if said contacts are initially engaged to couple said taps and said load means and if said contacts are initially disengaged to decouple said taps and said load; second mechanical switching means, also having a pair of metallic contacts, serially coupled between the other of said pair of first mechanical switching means metallic contacts an said load; semiconductor switching means coupled in parallel across said second mechanical switching means; and timing control means for closing said semiconductor switching means afTer closing of said first mechanical switching means by said control means and prior to closing of said second mechanical switching means by said control means to thereby effect current initiation between said taps and said load through said semiconductor switching means and for opening said semiconductor switching means after opening of said second mechanical switching means by said control means and prior to opening of said first mechanical switching means by said control means to thereby effect current interruption between said taps and said load across said semiconductor switching means; whereby said arcing, erosion, deterioration and the like is substantially lessened.

Claim 10

The combination as defined in claim 7, wherein said timing control means is included for opening said semiconductor switching means after opening of said second mechanical switching means by said control means and prior to opening of said first mechanical switching means by said control means.

Claim 11

The combination as defined in claim 8, wherein said timing control means is included for moving the contact arm of said first mechanical switching means from one of the plurality of said taps to another of the plurality of said taps, and to thereby effect closing of said first mechanical switching means metallic contacts.

Claim 12

Electric power switching apparatus as defined in claim 5 wherein said output circuit means includes a center tapped transformer.

Claim 13

The combination as defined in claim 9 wherein said load includes a center-tapped transformer.