Control circuit for driving an alternating current motor at a speed corresponding to the magnitude of a control signal and for braking the motor when the signal falls below a certain value

Claim 2

A control circuit for an alternating current motor comprising winding means to establish magnetic fields influencing the rotation of the motor in response to current flows in said winding means, a source of variable control signals, first control means operative when the magnitude of said control signals exceeds a predetermined value to provide current flows in said winding means which establish a rotating magnetic field for driving said motor in one direction at a speed in dependence on said magnitude of the control signals, and second control means operative when said magnitude of the control signals falls below said predetermined value to provide current flows in said winding means which establish a retarding magnetic field for braking the rotation of the motor in said one direction, and in which said winding means includes two windings, said first control means when operative connects said two windings in parallel and with a lead capacitor in series with one of said windings, and said second control means when operative connects said two windings in series with each other and in parallel with said lead capacitor.

Claim 3

A control circuit for an alternating current motor comprising winding means to establish magnetic fields influencing the rotation of the motor in response to current flows in said winding means, a source of variable control signals, first control means operative when the magnitude of said control signals exceeds a predetermined value to provide current flows in said winding means which establish a rotating magnetic field for driving said motor in one direction at a speed in dependence on said magnitude of the control signals, and second control means operative when said magnitude of the control signals falls below said predetermined value to provide current flows in said winding means which establish a retarding magnetic field for braking the rotation of the motor in said one direction, and in which said first control means includes a first transistor having said control signals applied thereto and being made conductive by said magnitude of the control signals exceeding said predetermined value with the impedance of the conductive first transistor varying in dependence on said magnitude of said control signals.

Claim 4

A control circuit for an alternating current motor comprising winding means to establish magnetic fields influencing the rotation of the motor in response to current flows in said winding means, a source of variable control signals, first control means operative when the magnitude of said control signals exceeds a predetermined value to provide current flows in said winding means which establish a rotating magnetic field for driving said motor in one direction at a speed in dependence on said magnitude of the control signals, and second control means operative when said magnitude of the control signals falls below said predetermined value to provide current flows in said winding means which establish a retarding magnetic field for braking the rotation of the motor in said one direction, and in which said first control means includes a first transistor having said control signals applied thereto and being made conductive by said magnitude of the control signals exceeding said predetermined value with the impedance of the conductive first transistor varying in dependence on said magnitude of said control signals.

Claim 5

A control circuit for an alternating current motor according to claim 2, in which said second control means includes a second transistor which, when conductive, provides said current flows in said winding means establishing said retarding magnetic field, and switch means responsive to said control signals to maintain said second transistor nonconductive so long as said magnitude of the control signals exceeds said predetermined value and to render said second transistor conductive when said magnitude of the control signals falls below said predetermined value.

Claim 6

A control circuit for an alternating current motor according to claim 3, in which said switch means includes a third transistor rendered conductive by said control signals only when the magnitude of the latter exceeds said predetermined value.

Claim 7

A control circuit for an alternating current motOr comprising winding means to establish magnetic fields influencing the rotation of the motor in response to current flows in said winding means, a source of variable control signals, first control means operative when the magnitude of said control signals exceeds a predetermined value to provide current flows in said winding means which establish a rotating magnetic field for driving said motor in one direction at a speed in dependence on said magnitude of the control signals, and second control means operative when said magnitude of the control signals falls below said predetermined value to provide current flows in said winding means which establish a retarding magnetic field for braking the rotation of the motor in said one direction, and in which said windings means includes two windings, said first control means includes a variable impedance element connected with said source of control signals to have its impedance varied inversely in accordance with said magnitude of the control signals, terminals receive an alternating current voltage for producing said current flows, circuit means connect said windings in parallel with each other to one of said terminals with a lead capacitor in series with one of said windings and with said variable impedance element interposed between said parallel connecting windings and the other of said terminals, and said second control means includes an element conductive only when said magnitude of the control signals falls below said predetermined value and connected between said other terminal and a junction in said circuit means between said lead capacitor and said one winding.

Claim 8

A control circuit for an alternating current motOr comprising winding means to establish magnetic fields influencing the rotation of the motor in response to current flows in said winding means, a source of variable control signals, first control means operative when the magnitude of said control signals exceeds a predetermined value to provide current flows in said winding means which establish a rotating magnetic field for driving said motor in one direction at a speed in dependence on said magnitude of the control signals, and second control means operative when said magnitude of the control signals falls below said predetermined value to provide current flows in said winding means which establish a retarding magnetic field for braking the rotation of the motor in said one direction, and in which said windings means includes two windings, said first control means includes a variable impedance element connected with said source of control signals to have its impedance varied inversely in accordance with said magnitude of the control signals, terminals receive an alternating current voltage for producing said current flows, circuit means connect said windings in parallel with each other to one of said terminals with a lead capacitor in series with one of said windings and with said variable impedance element interposed between said parallel connecting windings and the other of said terminals, and said second control means includes an element conductive only when said magnitude of the control signals falls below said predetermined value and connected between said other terminal and a junction in said circuit means between said lead capacitor and said one winding.

Claim 9

A control circuit for an alternating current motor according to claim 5, in which said variable impedance element is constituted by a first transistor having said control signals applied thereto so as to be conductive only when said magnitude of the control signals exceeds said predetermined value with the impedance of the conductive first transistor varying inversely with said magnitude, and full-wave rectifying means is connected with said circuit means and said first transistor to provide unidirectional current flow through the latter with alternating current flow through said windings.

Claim 10

A control circuit for an alternating current motor according to claim 6, in which said element of the second control means is constituted by a second transistor, said second control means further includes switch means responsive to said control signals to render said second transistor conductive only when said magnitude of the control signals falls below said predetermined value and diode means connected between said junction and said second transistor, and said second transistor is connected with said other terminal by way of said rectifying means.

Claim 11

A control circuit for an alternating current motor according to claim 7, in which said switch means includes a third transistor rendered conductive by said control signals only when the magnitude of the latter exceeds said predetermined value.

Claim 12

A control circuit for an alternating current motor according to claim 8, in which said one winding is interposed between said one terminal and said junction so that said lead capacitor is in series with said one winding when said first transistor is conducting and in series with the other of said windings when said second transistor is conducting.

Claim 13

A control circuit for an alternating current motor according to claim 8, in which said lead capacitor is interposed between said one terminal and said junction so that said lead capacitor is in series with said one winding when said first transistor is conducting and said windings are in series with each other and in parallel with said capacitor when said second transistor is conducting.