Means to promote the commutation of a thyristor switching arrangement for an electric motor at low motor speeds

Claim 2

An electric motor system comprising a direct current source; rotating machine means including a polyphase winding for producing a rotating magnetic field in either a stator or a rotor; switching means including a plurality of gate turn-on, nongate turn-off controlled rectifiers for connecting the individual windings on the polyphase winding to the direct current source by rendering the cOntrolled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the rotating machine; additional commutating means including an additional polyphase winding associated with said polyphase winding for promoting the turn-off of the controlled rectifiers by absorbing reactive power stored in said rotating machine means and applying a backward voltage to said controlled rectifiers to be turned off through said polyphase windings; and a polyphase alternating current source, having a number of phases equal to the number of polyphase windings, for supplying alternating current power to the additional commutating means.

Claim 3

An electric motor system comprising a direct current source, rotating machine means including a polyphase winding for producing a rotating magnetic field in either a stator or a rotor; switching means including a plurality of gate turn-on, nongate turn-off controlled rectifiers for connecting the individual windings of the polyphase winding to the direct current source by rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the rotating machine; additional commutating means associated with said polyphase winding for promoting the turn-off of the controlled rectifiers by applying a backward voltage to said controlled rectifiers to be turned off through said polyphase windings; and a polyphase alternating current source, having a number of phases equal to the number of polyphase windings, for supplying alternating current power to the additional commutating means, wherein said additional commutating means includes another polyphase winding which is magnetically coupled with the polyphase winding of said rotating machine on an iron core thereof in order to induce the backward voltage in the polyphase winding of the rotating machine by transformer action.

Claim 4

An electric motor system comprising a direct current source, rotating machine means including a polyphase winding for producing a rotating magnetic field in either a stator or a rotor; switching means including a plurality of gate turn-on, nongate turn-off controlled rectifiers for connecting the individual windings of the polyphase winding to the direct current source by rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the rotating machine; additional commutating means associated with said polyphase winding for promoting the turn-off of the controlled rectifiers by applying a backward voltage to said controlled rectifiers to be turned off through said polyphase windings; and a polyphase alternating current source, having a number of phases equal to the number of polyphase windings, for supplying alternating current power to the additional commutating means, wherein said additional commutating means includes another polyphase winding which is magnetically coupled with the polyphase winding of said rotating machine on an iron core thereof in order to induce the backward voltage in the polyphase winding of the rotating machine by transformer action.

Claim 5

An electric motor system comprising a direct current source; rotating machine means including a polyphase winding for producing a rotating magnetic field in either a stator or a rotor; switching means including a plurality of gate turn-on, nongate turn-off controlled rectifiers for connecting the individual windings of the polyphase winding to the direct current source by rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the rotating machine; additional commutating means including an additional polyphase winding associated with said polyphase winding for promoting the turn-off of the controlled rectifiers by absorbing reactive power stored in said rotating machine means and applying a backward voltage to said controlled rectifiers to be turned off through said polyphase windings; and a polyphase alternating current source, having a number of phases equal to the number of polyphase windings, for supplying alternating current power to the additional commutating means, wherein said additional commutating means includes a transformer having primary windings connected to the alternating current source, secondary windings connected with the polyphase windings and switch means for short-circuiting the secondary windings.

Claim 6

An electric motor system comprising a direct current source; rotating machine means including a polyphase winding for producing a rotating magnetic field in either a stator or a rotor; switching means including a plurality of gate turn-on, nongate turn-off controlled rectifiers for connecting the individual windings of the polyphase winding to the direct current source by rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the rotating machine; additional commutating means including an additional polyphase winding associated with said polyphase winding for promoting the turn-off of the controlled rectifiers by absorbing reactive power stored in said rotating machine means and applying a backward voltage to said controlled rectifiers to be turned off through said polyphase windings; and a polyphase alternating current source, having a number of phases equal to the number of polyphase windings, for supplying alternating current power to the additional commutating means, wherein said additional commutating means includes a transformer having primary windings connected to the alternating current source, secondary windings connected with the polyphase windings and switch means for short-circuiting the secondary windings.

Claim 7

An electric motor system according to claim 3, wherein said polyphase winding is star-connected, and said secondary windings are connected with each phase of the polyphase winding, respectively.

Claim 8

An electric motor system according to claim 3, wherein said polyphase winding is star-connected, the neutral point of which is opened by each phase, and each said secondary winding is respectively connected with the opened neutral points according to each phase.

Claim 9

An electric motor system comprising a direct current source; rotating machine means including a polyphase winding for producing a rotating magnetic field in either a stator of a rotor; switching means including a plurality of gate turn-on, nongAte turn-off controlled rectifiers for connecting the individual windings of the polyphase winding to the direct current source be rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the rotating machine; additional commutating means including an additional polyphase winding associated with said polyphase winding for promoting the turn-off of the controlled rectifiers by absorbing reactive power stored in said rotating machine means and applying a backward voltage to said controlled rectifiers to be turned off through said polyphase windings; and a polyphase alternating current source, having a number of phases equal to the number of polyphase windings, for supplying alternating current power to the additional commutating means, wherein means is provided to electrically disconnect said additional commutating means from said polyphase winding when said rotating machine starts up to a speed producing a voltage high enough to independently commutate said controlled rectifiers.

Claim 10

An electric motor system comprising a direct current source; rotating machine means including a polyphase winding for producing a rotating magnetic field in either a stator of a rotor; switching means including a plurality of gate turn-on, nongAte turn-off controlled rectifiers for connecting the individual windings of the polyphase winding to the direct current source be rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the rotating machine; additional commutating means including an additional polyphase winding associated with said polyphase winding for promoting the turn-off of the controlled rectifiers by absorbing reactive power stored in said rotating machine means and applying a backward voltage to said controlled rectifiers to be turned off through said polyphase windings; and a polyphase alternating current source, having a number of phases equal to the number of polyphase windings, for supplying alternating current power to the additional commutating means, wherein means is provided to electrically disconnect said additional commutating means from said polyphase winding when said rotating machine starts up to a speed producing a voltage high enough to independently commutate said controlled rectifiers.

Claim 11

An electrical control arrangement for increasing the starting counter electromotive force of a polyphase electric motor winding made up of winding portions selectively connected to a source of direct current by switching means including a plurality of gate turn-on, nongate turn-off controlled rectifiers under the control of means rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the motor, comprising an additional polyphase winding coupled with said polyphase electric motor winding, and a polyphase alternating current source, having a number of phases equal to the number of winding portions making up said polyphase electric motor winding, selectively connected to said additional polyphase winding for supplying alternating power thereto.

Claim 12

An electrical control arrangement for increasing the starting counter electromotive force of a polyphase electric motor winding made up of winding portions selectively connected to a source of direct current by switching means including a plurality of gate turn-on, nongate turn-off controlled rectifiers under the control of means rendering the controlled rectifiers conductive one after another in a predetermined order according to the relative position of the stator and the rotor of the motor, comprising an additional polyphase winding coupled with said polyphase electric motor winding, and a polyphase alternating current source, having a number of phases equal to the number of winding portions making up said polyphase electric motor winding, selectively connected to said additional polyphase winding for supplying alternating power thereto.

Claim 13

An electrical control arrangement as defined in claim 7, wherein said polyphase electric motor winding and said additional polyphase winding are magnetically coupled by means of an iron core.

Claim 14

An electrical control arrangement as defined in claim 7, wherein said additional polyphase winding is made up of secondary windings of a transformer, said transformer having an equal number of primary windings connected to said alternating current source and additional switch means for selectively short-circuiting said secondary windings.

Claim 15

An electrical control arrangement as defined in claim 9, wherein said polyphase winding is star-connected, and said secondary windings are connected with each phase of the polyphase winding, respectively.

Claim 16

An electrical control arrangement as defined in claim 9, wherein said polyphase winding is star-connected, the neutral point of which is opened by each phase, and each said secondary winding is respectively connected with the opened neutral points according to each phase.

Claim 17

An electrical control arrangement as defined in claim 7, wherein means is provided to electrically disconnect said additional polyphase winding from said alternating current source when the motor reaches a predetermined speed after starting sufficient to produce a counter electromotive force high enough to independently commutate said controlled rectifiers.