Dynamoelectric machine control circuit having current limiting means

Claim 2

A motor control circuit for operating a motor having an armature at a selected rated voltage comprising, first means to establish an error signal proportional to the difference between a desired motor operation at a selected rated voltage and the actual motor operation, second means to establish a compensating signal proportional to the counterelectromotive force of the armature of the motor, said last named means including negative current feedback means establishing a compensating voltage signal directly proportional to the armature current and forming a single combination circuit impedance compensating signal and an armature current limit signal, said compensating voltage signal being correspondingly scaled to the error signal and being equal to at least 30 percent of the corresponding scaled rated voltage to establish and maintain a continuous and smoothly changing transfer function including said compensating voltage signal, and motor control means responsive to said error signal and to said compensating signal.

Claim 3

The motor control circuit of claim 1, having supply lines connected to said motor and said current feedback means establishes said transfer function which is essentially independent of the resistance of the motor armature, the impedance of the supply lines and motor speed.

Claim 4

The motor control circuit of claim 1, including three-phase power distribution lines, and rectifying means connecting said armature essentially directly to said power distribution lines and having a gated means to selectively supply power line voltage to said armature, said control means being connected to selectively gate said gated means.

Claim 5

The motor control circuit of claim 1, wherein said first means establishes an essentially constant direct current level at any given motor operation deviation, said second means includes a full wave rectifying means establishing a direct current armature current related signal having a full wave ripple component and includes means to impress said related signal on said direct current error signal to establish a control signal, and said motor control means including means to establish an alternating current reference signal and establishing an operating signal in synchronism with a selected intercept of the control signal with said reference signal.

Claim 6

A motor control circuit for operating a motor at a selected rated voltage from a transformer supply means comprising, command signal means to establish a command signal proportional to a desired motor operation at a selected rated voltage, first feedback means to establish a feedback signal proportional to actual motor armature voltage, first summating means connected to said command signal means and to said feedback means to provide an error signal proportional to the algebraic sum of said command signal and said feedback signal, second feedback means to establish a second feedback signal proportional to the armature voltage and a third negative feedback signal proportional to the armature current, a second summating means connected to said first summating means and to said second feedback means to provide a summated control signal proportional to the algebraic sum of said error signal and said voltage and current feedback signals, said second and third feedback signals being of opposite polarity to establish a compensating signal related to the armature voltage drop, control means connected to said second summating means to control the current supplied to the armature, said third feedback signal establishing a continuous compensating armature current signal in excess of 25 percent of rated voltage and establishing a limit on the armature current supplied to the armature with the transfer function essentially independent of the impedance of the motor armature and the transformer supply means.

Claim 7

A motor control circuit for operating a motor at a selected rated voltage from a transformer supply means comprising, command signal means to establish a command signal proportional to a desired motor operation at a selected rated voltage, first feedback means to establish a feedback signal proportional to actual motor armature voltage, first summating means connected to said command signal means and to said feedback means to provide an error signal proportional to the algebraic sum of said command signal and said feedback signal, second feedback means to establish a second feedback signal proportional to the armature voltage and a third negative feedback signal proportional to the armature current, a second summating means connected to said first summating means and to said second feedback means to provide a summated control signal proportional to the algebraic sum of said error signal and said voltage and current feedback signals, said second and third feedback signals being of opposite polarity to establish a compensating signal related to the armature voltage drop, control means connected to said second summating means to control the current supplied to the armature, said third feedback signal establishing a continuous compensating armature current signal in excess of 25 percent of rated voltage and establishing a limit on the armature current supplied to the armature with the transfer function essentially independent of the impedance of the motor armature and the transformer supply means.

Claim 8

The motor control circuit of claim 5, having means to inversely vary the relative magnitude of the error signal and the third feedback signal for a given change in armature voltage and thereby vary the limit of the armature current.

Claim 9

The motor control circuit of claim 5, having an adjustable resistance means connecting the first summating means to the second summating means to vary the magnitude of the error signal for a given change in armature voltage and thereby vary the limit of the armature current.

Claim 10

The motor control circuit of claim 5, having a series connected adjustable potentiometer connecting the first summating means to the second summating means to vary the limit of the armature current.

Claim 11

The motor control circuit of claim 5, having gated means including an alternating current input and a periodic output, and gating means connecting the gated means to said second summating means and establishing a gating signal in response to the intercept of an alternating current reference voltage signal with the summated control signal from said second summating means.

Claim 12

The motor control circuit of claim 5, wherein said control means includes a gated rectifying means, including phase controlled rectifiers having an alternating current input and a direct current output and a firing means responsive to the intercept of said summated control signal and a reference voltage signal in a selected phase relationship with the voltage impressed upon said phase controlled rectifiers.

Claim 13

The motor control circuit of claim 5, wherein said control means including a three-phase full-wave rectifying means having an alternating current input and individual gated rectifiers for sequentially transmitting the sequential power phases as a direct current, said control means including an alternating current firing means in preselected phase relationship to said alternating current input, said first feedback means establishing a direct current feedback signal, said first summating means including an amplifier to provide a direct current error signal, said second feedback signal being a direct current proportional to the armature voltage and the third feedback signal being an unfiltered direct current signal proportional to current from a full wave rectifying means, said second summating means including an amplifier establishing said summated control signal, and means to impress said control signal on said firing means to control the firing of the gated rectifiers.

Claim 14

The motor control circuit of claim 11 wherein said armature current signal is of the order of 50 percent of rated voltage.

Claim 15

The motor control circuit of claim 11 wherein said armature current signal is in the range of 25 percent to 80 percent of rated voltage.