Voltage control of an ac drive system during motor starting

Claim 2

In an a-c drive system including a source of adjustable voltage a-c electric power and a plurality of synchronous motors coupled to the source for receiving electric power therefrom, control means comprising: first means coupled to the source for sensing a selected output parameter thereof having a magnitude which varies substantially from its steady state level during the starting of one or more of the motors and for producing a first control signal having a magnitude representative of the magnitude of the selected output parameter, second means coupled to said first means for receiving first control signals therefrom and producing in response to a substantial change in a first control signal a second control signal, third means coupled to said second means for receiving second control signals therefrom and producing in response to a second control signal a third control signal having a predetermined duration following the initial reception of the second control signal, and fourth means coupled to the source for controlling the output voltage of the electric power supplied therefrom, said fourth means also coupled to said third means for receiving third control signals therefrom and responding to a third control signal by changing the voltage of the electric power supplied by the source throughout the predetermined duration of the third control signal.

Claim 3

Control means as defined by claim 1 in which the selected output parameter sensed by said first means is the component of output current that is in phase with the output voltage of the source.

Claim 4

Control means as defined by claim 1 in which the magnitude of third control signals produced by said third means is independent of the respective magnitudes of the changes in the first control signal.

Claim 5

Control means as defined by claim 1 in which the selected output parameter sensed by said first means increases during the starting of one or more of the motors, in which said second means comprises means for producing second control signals in response to substantial increases or decreases in the selected output parameter as represented by respective increases or decreases of first control signals, in which said means comprises means for generating third control signals only in response to second control signals produced in response to increases in first control signals, and in which said fourth means increases the output voltage of the source throughout the predetermined duration of third control signals, whereby the output voltage of the source is automatically increased during the starting of onE or more motors so as to implement rapid synchronization of the motors being started without changing the operating speed of previously synchronized motors.

Claim 6

Control means as defined by claim 4 in which the selected output parameter sensed by said first means is the component of output current that is in phase with the output voltage of the source.

Claim 7

Control means as defined by claim 4 in which said second means includes means for producing second control signals of different polarity in response to, respectively, increases and decreases in the first control signal, and in which said third means includes uni-directional input means selected so as to transmit only second control signals produced in response to increases in the first control signal.

Claim 8

Control means as defined by claim 6 in which the magnitude of third control signals produced by said third means is independent of the magnitude of second control signals transmitted by said unidirectional input means.

Claim 9

Control means as defined by claim 7 in which said third means further comprises means for maintaining the magnitude of third control signals substantially constant throughout the predetermined duration.

Claim 10

Control means as defined by claim 7 in which said third means further comprises means for adjusting the predetermined duration of third control signals and means for adjusting the magnitude of third control signals.

Claim 11

Control means as defined by claim 9 in which said third means further comprises means for maintaining the magnitude of third control signals substantially constant throughout the predetermined duration.

Claim 12

An adjustable speed drive system comprising: an inverter for supplying adjustable frequency, adjustable voltage electric power, a plurality of synchronous motors coupled to said inverter for receiving electric power therefrom, means for independently starting and stopping said motors, first means coupled to said inverter for sensing a selected output parameter thereof which increases substantially from its steady state level during the starting of one or more of the motors and for producing a first control signal having a magnitude representative of the magnitude of the selected output parameter, second means coupled to said first means for receiving first control signals therefrom and producing in response to a substantial change in a first control signal a second control signal, third means coupled to said second means for receiving second control signals therefrom and producing in response to a second control signal responsive to an increase in a first control signal a third control signal having a predetermined duration following the initial reception of the second control signal, and fourth means coupled to said inverter forcontrolling the output frequency and the output voltage of the electric power supplied therefrom, said fourth means also coupled to said third means for receiving third control signals therefrom and responding to a third control signal by increasing the output voltage of said inverter throughout the predetermined duration of the third control signal, whereby the output voltage of said inverter is automatically increased during the starting of one or more motors so as to implement rapid synchronization of the motors being started without changing the operating speed of previously synchronized motors.

Claim 13

An adjustable speed drive system comprising: an inverter for supplying adjustable frequency, adjustable voltage electric power, a plurality of synchronous motors coupled to said inverter for receiving electric power therefrom, means for independently starting and stopping said motors, first means coupled to said inverter for sensing a selected output parameter thereof which increases substantially from its steady state level during the starting of one or more of the motors and for producing a first control signal having a magnitude representative of the magnitude of the selected output parameter, second means coupled to said first means for receiving first control signals therefrom and producing in response to a substantial change in a first control signal a second control signal, third means coupled to said second means for receiving second control signals therefrom and producing in response to a second control signal responsive to an increase in a first control signal a third control signal having a predetermined duration following the initial reception of the second control signal, and fourth means coupled to said inverter forcontrolling the output frequency and the output voltage of the electric power supplied therefrom, said fourth means also coupled to said third means for receiving third control signals therefrom and responding to a third control signal by increasing the output voltage of said inverter throughout the predetermined duration of the third control signal, whereby the output voltage of said inverter is automatically increased during the starting of one or more motors so as to implement rapid synchronization of the motors being started without changing the operating speed of previously synchronized motors.

Claim 14

Control means as defined by claim 11 in which said second means includes means for producing second control signals of different polarity in response to, respectively, increases and decreases in the first control signal and in which said third means includes unidirectional input means selected so as to transmit only second control signals produced in response to increases in the first control signal.

Claim 15

Control means as defined by claim 12 in which the magnitude of third control signals produced by said third means is independent of the magnitude of second control signals transmitted by said unidirectional Input means.

Claim 16

Control means as defined by claim 13 in which said third means further comprises means for maintaining the magnitude of third control signals substantially constant throughout the predetermined duration.

Claim 17

Control means as defined by claim 14 in which said third means further comprises means for adjusting the predetermined duration of third control signals and means for adjusting the magnitude of third control signals.

Claim 18

Control means as defined by claim 15 in which the selected output parameter sensed by said first means is the component of output current that is in phase with the output voltage of said inverter.