Control system for polyphase induction machines

Claim 3

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator responsive to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; said relay having a given drop-out time which is greater than the time period required to reduce each said output control signal from its maximum value to a value which removes said operating voltage from said motor; and a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits when said first signal is greater than said second signal.

Claim 4

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator responsive to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; said relay having a given drop-out time which is greater than the time period required to reduce each said output control signal from its maximum value to a value which removes said operating voltage from said motor; and a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits when said first signal is greater than said second signal.

Claim 5

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator responsive to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; said acceleration signal generator including means for electrically decoupling said acceleration signal generator from said motor control input wherein said acceleration signal generator provides said first signal in response to the energizing of said coil while electrically isolating said acceleration signal generator from said coil; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; and a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits which said first signal is greater than said second level.

Claim 6

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator responsive to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; said acceleration signal generator including means for electrically decoupling said acceleration signal generator from said motor control input wherein said acceleration signal generator provides said first signal in response to the energizing of said coil while electrically isolating said acceleration signal generator from said coil; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; and a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits which said first signal is greater than said second level.

Claim 7

The system according to claim 3, wherein said means for decoupling includes an opto-coupler device which provides an output transition triggered by light illumination thereon in response to an electrical input signal provided by said motor control input.

Claim 8

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator responsive to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits when said first signal is greater than said second signal; and, said comparators being electrically isolated from said output circuits by way of an opto coupler device respectively coupled between the output of each comparator and said output circuits.

Claim 9

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator responsive to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits when said first signal is greater than said second signal; and, said comparators being electrically isolated from said output circuits by way of an opto coupler device respectively coupled between the output of each comparator and said output circuits.

Claim 10

The system according to claim 5, wherein said motor is a 3-phase induction motor having a squirrel-cage rotor and wherein said polyphase voltage is a 3-phase voltage.

Claim 11

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator response to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; said acceleration signal generator including a ramp generator which includes an initial voltage offset circuit wherein the initial level of said first signal is a predetermined valve greater than zero; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits when said first signal is greater than said second signal; each output circuit including a triac device having first and second main electrodes serially coupled between said motor and said means for supplying voltage and said triac device having a control gate input electrode coupled to the output of the corresponding comparator; and each control gate input electrode begin coupled to said corresponding comparator by an opto coupler which respectively electrically isolates the corresponding comparator from said output circuits.

Claim 12

A control system for controlling the start-up sequence of a polyphase electric motor in response to a motor control input, said system comprising, in combination: a motor control circuit for providing said motor control input; means including a relay having an energizing coil coupled to said motor control input for supplying polyphase operating voltage to said motor and cooperating with said motor control circuit for both forward and reverse motor operations; a plurality of output circuits respectively coupled between said motor and said means for supplying voltage, each output circuit being responsive to an output control signal applied to an input thereof for applying said operating voltage to said motor; an acceleration signal generator response to said motor control input including means for providing a first signal which gradually increases upon the initial application of said operating voltage; said acceleration signal generator including a ramp generator which includes an initial voltage offset circuit wherein the initial level of said first signal is a predetermined valve greater than zero; a plurality of phase control signal generators respectively coupled to each phase of said operating voltage for providing a second output signal which decreases from a given level during each one of successive cycles of said phase of said operating voltage; a plurality of comparators with each comparator having first and second inputs respectively coupled to receive said common first signal and said second signals and each comparator having an output for respectively applying said output control signal to said input of each of said output circuits when said first signal is greater than said second signal; each output circuit including a triac device having first and second main electrodes serially coupled between said motor and said means for supplying voltage and said triac device having a control gate input electrode coupled to the output of the corresponding comparator; and each control gate input electrode begin coupled to said corresponding comparator by an opto coupler which respectively electrically isolates the corresponding comparator from said output circuits.