Full-wave adjustable motor speed control system with feedback

Claim 2

In a motor control system having a motor power circuit including the armature winding of the motor connected to an alternating current source, a motor speed control system for adjusting and regulating the motor speed comprising: a switching device of the gating-type connected in the motor power circuit for controlling the amount of power applied to the motor; a firing control circuit supplied from said source for supplying a firing pulse to said switching device on each half-cycle of the alternating current source and including adjustable means for adjusting the firing angle of said pulses thereby to adjust the motor speed; and a speed sensing feedback circuit connected to the motor comprising: means for developing a feedback voltage that is proportional to the motor speed and independent of the magnitude of the motor current thereby to provide a true speed signal; and means for applying said feedback voltage to said firing control circuit to regulate the motor speed under varying load conditions; said means for developing a feedback voltage comprising: means for integrating the voltage appearing across the motor armature circuit; and means for balancing out the voltage drop due to the resistance of the motor armature circuit to develop in said integrating means only a voltage proportional to the motor speed which is the feedback voltage.

Claim 3

In a motor control system having a motor power circuit including the armature winding of the motor connected to an alternating current source, a motor speed control system for adJusting and regulating the motor speed comprising: an alternating current bidirectional switching device of the gating-type connected in the motor power circuit for controlling the amount of AC power applied to the motor; a firing control circuit supplied from said source for supplying a firing pulse to said switching device on each half-cycle of the alternating current source and including adjustable means for adjusting the firing angle of said pulses thereby to adjust the motor speed; and a speed sensing feedback circuit connected to the motor comprising: means for developing a feedback voltage that is proportional to the motor speed and independent of the magnitude of the motor current thereby to provide a true speed signal; and means for applying said feedback voltage to said firing control circuit to regulate the motor speed under varying load conditions; said means for developing a feedback voltage comprising: means responsive to the current in the motor armature circuit for subtracting from the armature circuit voltage the portion thereof attributable to the voltage drop due to motor armature circuit resistance to provide a resultant voltage proportional to motor counter EMF as a true speed signal: and means for integrating said resultant voltage on positive half-cycles of the source voltage and for maintaining it on alternate negative half-cycles.

Claim 4

In a motor control system having a motor power circuit including the armature winding of the motor connected to an alternating current source, a motor speed control system for adJusting and regulating the motor speed comprising: an alternating current bidirectional switching device of the gating-type connected in the motor power circuit for controlling the amount of AC power applied to the motor; a firing control circuit supplied from said source for supplying a firing pulse to said switching device on each half-cycle of the alternating current source and including adjustable means for adjusting the firing angle of said pulses thereby to adjust the motor speed; and a speed sensing feedback circuit connected to the motor comprising: means for developing a feedback voltage that is proportional to the motor speed and independent of the magnitude of the motor current thereby to provide a true speed signal; and means for applying said feedback voltage to said firing control circuit to regulate the motor speed under varying load conditions; said means for developing a feedback voltage comprising: means responsive to the current in the motor armature circuit for subtracting from the armature circuit voltage the portion thereof attributable to the voltage drop due to motor armature circuit resistance to provide a resultant voltage proportional to motor counter EMF as a true speed signal: and means for integrating said resultant voltage on positive half-cycles of the source voltage and for maintaining it on alternate negative half-cycles.

Claim 5

The invention defined in claim 2, wherein said subtracting means comprises: a signal resistor in the motor armature circuit; and a current amplifier responsive to the voltage across said signal resistor for reducing the voltage applied to said integrating means.

Claim 6

The invention defined in claim 2, wherein said means for integrating the voltage comprises: a resistance-capacitance circuit connected across said motor armature circuit; and a unidirectional current conducting device in said resistance-capacitance circuit for allowing current flow therein only on each positive half-cycle of the source voltage.

Claim 7

In a motor control system having a motor power circuit including the armature of an electric motor connected to an alternating current source, a motor speed control system for adjusting and regulating the motor speed comprising: a bidirectional thyristor triode having a pair of anodes connected in the motor power circuit and a gate; a firing control circuit supplied from said source for supplying firing pulses to said gate on the half-cycles of the source voltage and including adjustable means for adjusting the firing angle of said pulses thereby to adjust the motor speed; and feedback voltage means for regulating the firing angle of said pulses to compensate for speed change under varying load comprising: means for canceling the portion of the voltage due to the resistance drop in said motor armature circuit to leave a resultant voltage proportional to the motor counter EMF that is proportional to motor speed; means for integrating said resultant voltage on positive half-cycles of the source voltage and for maintaining such integrated voltage during the alternate negative half-cycles as the feedback voltage; and means for applying said feedback voltage to said firing control circuit to compensate for speed change under varying load.

Claim 8

In a motor control system having a motor power circuit including the armature of an electric motor connected to an alternating current source, a motor speed control system for adjusting and regulating the motor speed comprising: a bidirectional thyristor triode having a pair of anodes connected in the motor power circuit and a gate; a firing control circuit supplied from said source for supplying firing pulses to said gate on the half-cycles of the source voltage and including adjustable means for adjusting the firing angle of said pulses thereby to adjust the motor speed; and feedback voltage means for regulating the firing angle of said pulses to compensate for speed change under varying load comprising: means for canceling the portion of the voltage due to the resistance drop in said motor armature circuit to leave a resultant voltage proportional to the motor counter EMF that is proportional to motor speed; means for integrating said resultant voltage on positive half-cycles of the source voltage and for maintaining such integrated voltage during the alternate negative half-cycles as the feedback voltage; and means for applying said feedback voltage to said firing control circuit to compensate for speed change under varying load.

Claim 9

The invention defined in claim 5, wherein said means for canceling comprises: an amplifier for shunting current from said integrating means; and means responsive to the value of motor current for controlling said amplifier in proportion thereto.

Claim 10

In a motor control system having a motor power circuit including the armature of an electric motor connected to an alternating current source, a motor speed control system for adjusting and regulating the motor speed comprising: a bidirectional thyristor triode connected by its main electrodes in the motor power circuit for controlling the amount of power applied to the motor thereby to control its speed; A firing control circuit supplied from said source for supplying a firing pulse to the gate electrode of said triode on each half-cycle of the source voltage appearing on the main electrodes thereof and including: means for developing a pedestal voltage during each half-cycle of the source voltage; means for developing a ramp voltage during each half-cycle of the source voltage and superimposed it on the corresponding pedestal voltage; means operable when the sum of said pedestal and ramp voltages reaches a predetermined value for applying a firing pulse to the gate electrode of said triode; and adjustable means for varying the height of said pedestal voltage thereby to control the firing angle of said triode on each half-cycle of the source voltage; said motor speed control system further comprising: feedback voltage means for regulating the height of said pedestal voltage including: a motor current sensing device in the motor power circuit; means including said motor current sensing device for removing the portions of the voltage due to the voltage drop caused by armature resistance and the voltage drop across said motor current sensing device to leave a resultant voltage proportional to the motor counter EMF that is proportional to motor speed; means for integrating said resultant voltage on positive half-cycles of the source voltage and for maintaining such integrated voltage during the alternate negative half-cycles as the feedback voltage; and means for applying said feedback voltage to regulate the height of said pedestal voltage to maintain the motor speed constant under varying load.

Claim 11

In a motor control system having a motor power circuit including the armature of an electric motor connected to an alternating current source, a motor speed control system for adjusting and regulating the motor speed comprising: a bidirectional thyristor triode connected by its main electrodes in the motor power circuit for controlling the amount of power applied to the motor thereby to control its speed; A firing control circuit supplied from said source for supplying a firing pulse to the gate electrode of said triode on each half-cycle of the source voltage appearing on the main electrodes thereof and including: means for developing a pedestal voltage during each half-cycle of the source voltage; means for developing a ramp voltage during each half-cycle of the source voltage and superimposed it on the corresponding pedestal voltage; means operable when the sum of said pedestal and ramp voltages reaches a predetermined value for applying a firing pulse to the gate electrode of said triode; and adjustable means for varying the height of said pedestal voltage thereby to control the firing angle of said triode on each half-cycle of the source voltage; said motor speed control system further comprising: feedback voltage means for regulating the height of said pedestal voltage including: a motor current sensing device in the motor power circuit; means including said motor current sensing device for removing the portions of the voltage due to the voltage drop caused by armature resistance and the voltage drop across said motor current sensing device to leave a resultant voltage proportional to the motor counter EMF that is proportional to motor speed; means for integrating said resultant voltage on positive half-cycles of the source voltage and for maintaining such integrated voltage during the alternate negative half-cycles as the feedback voltage; and means for applying said feedback voltage to regulate the height of said pedestal voltage to maintain the motor speed constant under varying load.

Claim 12

The invention defined in claim 7, wherein said means for integrating the voltage comprises: a unidirectional current conducting resistance-capacitance circuit connected across said motor armature and motor current sensing device.

Claim 13

The invention defined in claim 8, wherein said means including said motor current sensing device for removing the portions of the voltage comprises: a transistor amplifier responsive to the voltage across said motor current sensing device for shunting current from the capacitor in proportion thereto.

Claim 14

The invention defined in claim 9, wherein said means for applying said feedback voltage comprises: means connecting the voltage of said capacitor as a feedback voltage through said adjustable means to regulate the height of said pedestal voltage to compensate for variation in motor speed.