Electric motor controller with bypass contactor

Claim 1

An apparatus for controlling an electric motor which is supplied by a source of alternating voltage, said apparatus comprising: of alternating voltage to the motor in response to a control signal; a thyristor switch means for selectively coupling the source of alternating voltage to the motor in response to a trigger signal; a control circuit for operating said contactor assembly and said thyristor switch means, and including: (a) a first means for producing the control signal for said contactor assembly, and being responsive to a command to stop the motor by discontinuing the production of the control signal for said contactor means; and (b) a second means, responsive to the command to stop the motor, for producing trigger signals for said thyristor switch means to reduce the speed of the motor; and (c) means for synchronizing the production of trigger signals by said stopping means to the alternating voltage.

Claim 2

An apparatus for controlling an electric motor which is supplied by a source of alternating voltage, said apparatus comprising: of alternating voltage to the motor in response to a control signal; a thyristor switch means for selectively coupling the source of alternating voltage to the motor in response to a trigger signal; a control circuit for operating said contactor assembly and said thyristor switch means, and including: (a) a first means for producing the control signal for said contactor assembly, and being responsive to a command to stop the motor by discontinuing the production of the control signal for said contactor means; and (b) a second means, responsive to the command to stop the motor, for producing trigger signals for said thyristor switch means to reduce the speed of the motor; and (c) means for synchronizing the production of trigger signals by said stopping means to the alternating voltage.

Claim 8

An apparatus for controlling an electric motor which is supplied by a three-phase source of alternating voltage, said apparatus comprising: a contactor for selectively connecting the source of alternating voltage to the motor in response to a control signal; three thyristor switch means, each one for selectively coupling a phase of the source of alternating voltage to the motor in response to a trigger signal; a control circuit for operating said contactor and said thyristor switch means, and having a first mode of operation for starting said motor by producing a series trigger signals which place said thyristor switch means in a conductive state during progressively longer intervals during half-cycles of the alternating voltage, a second mode in which the trigger signals are not being produced and in which said control circuit produces the control signal causing said contactor to connect the source of alternating voltage to the motor, and a third mode for stopping the motor in which said contactor is deactivated and said thyristor switch means are triggered in a defined sequence to reduce the speed of the motor. motor stoppage initiation means for translating the control circuit from the second mode to the third mode by triggering all of said thyristor switch means substantially simultaneously, detecting which one of said thyristor switch means becomes non-conducting first, and beginning the triggering by the control circuit at a point in the defined sequence where the one thyristor switch means is triggered.

Claim 9

An apparatus for controlling an electric motor which is supplied by a three-phase source of alternating voltage, said apparatus comprising: a contactor for selectively connecting the source of alternating voltage to the motor in response to a control signal; three thyristor switch means, each one for selectively coupling a phase of the source of alternating voltage to the motor in response to a trigger signal; a control circuit for operating said contactor and said thyristor switch means, and having a first mode of operation for starting said motor by producing a series trigger signals which place said thyristor switch means in a conductive state during progressively longer intervals during half-cycles of the alternating voltage, a second mode in which the trigger signals are not being produced and in which said control circuit produces the control signal causing said contactor to connect the source of alternating voltage to the motor, and a third mode for stopping the motor in which said contactor is deactivated and said thyristor switch means are triggered in a defined sequence to reduce the speed of the motor. motor stoppage initiation means for translating the control circuit from the second mode to the third mode by triggering all of said thyristor switch means substantially simultaneously, detecting which one of said thyristor switch means becomes non-conducting first, and beginning the triggering by the control circuit at a point in the defined sequence where the one thyristor switch means is triggered.

Claim 11

An apparatus for controlling an electric motor which is supplied by a three-phase source of alternating electricity, said apparatus comprising: a contactor assembly connecting each phase of the source of alternating electricity to the motor in response to a control signal; three thyristor switch means, each coupling one phase of the source to the motor when rendered conductive by a trigger signal; a control circuit for operating said contactor assembly and said three thyristor switch means, and including: (a) means for discontinuing the application of the control signal to the contactor assembly in response to a command to stop the motor; (b) means for sensing when said contactor assembly is not connecting at least one of the source phases to the motor; (c) means, responsive to said means for sensing, for triggering said three thyristor switch means substantially at the same time; (d) means for detecting when one of the thyristor switch means is not conducting electricity after being triggered; and (e) means for triggering each of said thyristor switch means in a given sequence to reduce the speed of the motor, wherein the triggering commences at a point in the sequence whereat the one thyristor switch means is triggered first.

Claim 12

An apparatus for controlling an electric motor which is supplied by a three-phase source of alternating electricity, said apparatus comprising: a contactor assembly connecting each phase of the source of alternating electricity to the motor in response to a control signal; three thyristor switch means, each coupling one phase of the source to the motor when rendered conductive by a trigger signal; a control circuit for operating said contactor assembly and said three thyristor switch means, and including: (a) means for discontinuing the application of the control signal to the contactor assembly in response to a command to stop the motor; (b) means for sensing when said contactor assembly is not connecting at least one of the source phases to the motor; (c) means, responsive to said means for sensing, for triggering said three thyristor switch means substantially at the same time; (d) means for detecting when one of the thyristor switch means is not conducting electricity after being triggered; and (e) means for triggering each of said thyristor switch means in a given sequence to reduce the speed of the motor, wherein the triggering commences at a point in the sequence whereat the one thyristor switch means is triggered first.

Claim 13

A method for controlling the speed of an electric motor which is selectively coupled to a three-phase source of alternating electricity by a contactor and three thyristor switch means, said method comprising: activating the contactor to couple the motor to the source; deactivating the contactor in response to a command to stop the motor; thereafter triggering the thyristor switch means; detecting the first one of the triggered thyristor switch means to become non-conducting; retriggering the first one of the thyristor switch means; and thereafter, sequentially triggering each of the thyristor switch means in a pattern which reduces the speed of the motor.

Claim 14

A method for controlling the speed of an electric motor which is selectively coupled to a three-phase source of alternating electricity by a contactor and three thyristor switch means, said method comprising: activating the contactor to couple the motor to the source; deactivating the contactor in response to a command to stop the motor; thereafter triggering the thyristor switch means; detecting the first one of the triggered thyristor switch means to become non-conducting; retriggering the first one of the thyristor switch means; and thereafter, sequentially triggering each of the thyristor switch means in a pattern which reduces the speed of the motor.