Electrical switching device

Claim 2

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts operable to an open and a closed condition for completing an electrically conductive path and electrically energized operating means for opening and closing said contacts, and a control circuit for controlling the energization of said operating means to switch said load on and off, said control circuit comprising oppositely directed asymmetrically conducting elements and switching elements operable to close said first contactor contacts to connect the load to said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor contacts during a halfcycle in which said rectifier is conductive thereby applying an input current to said load, and operable to open said second contactor contacts during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor contacts during a half-cycle in which said rectifier is non-conductive thereby removing said input current from said load.

Claim 3

A device as claimed in claim 1, wherein the control circuit for controlling the operation of said contactors includes at least one voltage-sensitive device which determines the part of the respective half-cycle in which the operating means of said contactors are energized.

Claim 4

A device as claimed in claim 2, wherein said voltage-sensitive device or each of said voltage-sensitive devices is a zener diode.

Claim 5

A device as claimed in claim 1, for use with capacitive loads, wherein energization of each of said operating means takes place immediately after the supply voltage has passed through zero.

Claim 6

A device as claimed in claim 1, wherein the contactors are controlled by a control quantity derived from the supply voltage.

Claim 7

A device as claimed in claim 1, wherein the contactors are controlled by a control quantity derived from the load current.

Claim 8

A device as claimed in claim 1, wherein the response time of each contactor is shorter tHan half the period of the supply voltage.

Claim 9

A device as claimed in claim 1, wherein means is provided for electrically pre-energizing the contactors.

Claim 10

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operations of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said first contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, wherein the energizing current used to operate the contactors is higher than the nominal energizing current, and wherein circuit elements are provided to limit the time of application of this excess current.

Claim 11

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operations of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said first contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, wherein the energizing current used to operate the contactors is higher than the nominal energizing current, and wherein circuit elements are provided to limit the time of application of this excess current.

Claim 12

A device as claimed in claim 9, wherein said circuit elements are selected from the group consisting of capacitors, start and stop keys having wiper contacts, and positive temperature coefficient resistors.

Claim 13

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operating of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said first contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half-cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, wherein the contactors are bistable.

Claim 14

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operating of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said first contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half-cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, wherein the contactors are bistable.

Claim 15

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operating of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said first contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half-cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, and further includIng an auxiliary contactor having normally open contacts in the load circuit, said contacts being effective when closed to reduce the load on the contacts of the first and second contactors, wherein means are provided for energizing said auxiliary contactor at switch-on after the closure of the contacts of the second contactor.

Claim 16

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operating of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said first contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half-cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, and further includIng an auxiliary contactor having normally open contacts in the load circuit, said contacts being effective when closed to reduce the load on the contacts of the first and second contactors, wherein means are provided for energizing said auxiliary contactor at switch-on after the closure of the contacts of the second contactor.

Claim 17

A device as claimed in claim 12, wherein said auxiliary contactor has a plurality of normally open contacts connected in parallel in the load circuit.

Claim 18

A device as claimed in claim 12, wherein the auxiliary contactor has a normally closed contact serving, at switch-off, to delay the opening of the contacts of the first and second contactors until the normally open contacts of the auxiliary contactor are open.

Claim 19

A device as claimed in claim 14, wherein said normally open and normally closed contacts are constituted by change-over contacts.

Claim 20

A device as claimed in claim 12, including means for ensuring that the contacts of the auxiliary contactor close after the closing of the contacts of the second contactor, and on the other hand that the operating means of the first and second contactors can only be energized after the contacts of the auxiliary contactor have opened.

Claim 21

A device as claimed in claim 12, for use in polyphase circuits, wherein a single auxiliary contactor is provided for all the phases and wherein operation of said auxiliary contactor is delayed by means of a delay element until all the first and second contactors in the various phases are closed.

Claim 22

A device as claimed in claim 17, wherein said delay element is a negative-temperature-coefficient resistor.

Claim 23

A device as claimed in claim 17, wherein the delay element is electrically shunted during the time of operation of the auxiliary contactor by normally open contacts of the auxiliary contactor.

Claim 24

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operating of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half-cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, and including another rectifier connected in series with the contacts of said second contactor, wherein the two series combinations of rectifiers and contacts are arranged in parallel with one another, said rectifiers having opposite polarities to one another; and wherein means are provided for operating the two contactors in such a way that both at switch-on and at switch-off the contacts of each of the contactors are closed and opened respectively only during a time interval in which the particular rectifier in series therewith is non-conducting.

Claim 25

A hybrid switching device for connecting a load to an alternating current supply, comprising a half-wave rectifier, a first contactor connected in series with said rectifier between said load and said supply, a second contactor connected in parallel with said rectifier, each of said contactors comprising contacts and operating means and a control circuit for controlling the operating of said contactors to switch said load on or off, said control circuit comprising oppositely directed asymmetrically conducting means and switching elements operable in switching said load ''''on'''' first and exclusively to close said contactor to connect the load to the supply through said rectifier during a half-cycle in which said rectifier is non-conductive and thereafter to close said second contactor during a half-cycle in which said rectifier is conductive, and operable in switching said load ''''off'''' first and exclusively to open said second contactor during a half-cycle in which said rectifier is conductive and thereafter to open said first contactor during a half-cycle in which said rectifier is non-conductive, and including another rectifier connected in series with the contacts of said second contactor, wherein the two series combinations of rectifiers and contacts are arranged in parallel with one another, said rectifiers having opposite polarities to one another; and wherein means are provided for operating the two contactors in such a way that both at switch-on and at switch-off the contacts of each of the contactors are closed and opened respectively only during a time interval in which the particular rectifier in series therewith is non-conducting.