Braking-mode detection circuit

Claim 2

A circuit for sensing operation of a direct current motor having an armature and a field winding in a braking mode comprising: first sensing means for sensing the magnitude of armature current and outputting a first signal representative thereof; second sensing means for outputting a second signal representative of motor terminal voltage; output means responsive to said first and said second signals to produce an output signal when the ratio of armature current to motor terminal voltage attaIns a predetermined value.

Claim 3

A braking-mode detection circuit for use with a time-ratio control system for controlling operation of a direct current motor having a field winding and an armature winding comprising: first sensing means for producing a signal representative of armature current; second sensing means for producing a signal representative of the average conductivity of the time-ratio control system; output means coupled to said first and said second sensing means and operative to produce a signal for modifying the operation of said time ratio control system when said signals produced by said first and said second sensing means achieve a predetermined relationship.

Claim 4

A braking-mode detection circuit for use with a time-ratio control system for controlling operation of a direct current motor having a field winding and an armature winding comprising: first sensing means for producing a signal representative of armature current; second sensing means for producing a signal representative of the average conductivity of the time-ratio control system; output means coupled to said first and said second sensing means and operative to produce a signal for modifying the operation of said time ratio control system when said signals produced by said first and said second sensing means achieve a predetermined relationship.

Claim 5

The invention defined in claim 2, wherein said output means serves to lessen the average conductivity of the time ratio control system for reducing the voltage applied to the DC motor.

Claim 6

In an electric vehicle powered by a direct current traction motor having an armature winding and a field winding, means for reversibly connecting the field winding to effect motor braking, the operation of said traction motor being controlled by a time-ratio control system comprising power switching means and means for modifying the mark-space conductive ratio of the power switching means, a braking mode detection circuit comprising: first means coupled to said armature for producing a first signal proportional to armature current; second means coupled to said control system for producing a second signal proportional to the mark-space ratio of said power switch; and output means coupled to said first and said second means and operative to decrease the mark-space ratio of said power switching means when said first and said second signals achieve a predetermined ratio.

Claim 7

In an electric vehicle powered by a direct current traction motor having an armature winding and a field winding, means for reversibly connecting the field winding to effect motor braking, the operation of said traction motor being controlled by a time-ratio control system comprising power switching means and means for modifying the mark-space conductive ratio of the power switching means, a braking mode detection circuit comprising: first means coupled to said armature for producing a first signal proportional to armature current; second means coupled to said control system for producing a second signal proportional to the mark-space ratio of said power switch; and output means coupled to said first and said second means and operative to decrease the mark-space ratio of said power switching means when said first and said second signals achieve a predetermined ratio.

Claim 8

The invention defined in claim 4 wherein said output means comprises a comparator.

Claim 9

The invention defined in claim 5 wherein said first sensing means comprises a resistive current shunt coupled in circuit with said armature.

Claim 10

In a control circuit including a gated switch for controllably metering power to a DC motor having an armature and a field winding, means for indicating the operation of the motor in the braking mode, comprising: first means for producing a first signal indicative of the magnitude of the armature current; second means for producing a second signal indicative of the conduction to non-conduction time ratio of the gated switch; means coupled to said first and said second means for receiving said first and said second signals and producing an output signal when said first and said second signals exceed predetermined values.

Claim 11

In a control circuit including a gated switch for controllably metering power to a DC motor having an armature and a field winding, means for indicating the operation of the motor in the braking mode, comprising: first means for producing a first signal indicative of the magnitude of the armature current; second means for producing a second signal indicative of the conduction to non-conduction time ratio of the gated switch; means coupled to said first and said second means for receiving said first and said second signals and producing an output signal when said first and said second signals exceed predetermined values.

Claim 12

The invention defined in claim 7, further including utilization means coupled to said last-named means for reducing the conduction to non-conduction time ratio of the gated switch upon receipt of said output signal.

Claim 13

The invention defined in claim 8, wherein said first means is a resistive current shunt.

Claim 14

In a control circuit including gated thyristor means for metering power to a DC motor having an armature and a field winding, means for controlling the amount of power so metered during motor braking comprising: control means for gating the thyristor means to effect a predetermined mark-space ratio; first means adapted to be coupled to the armature for producing a signal indicative of the current flowing therethrough; second means producing a signal indicative of the mark-space ratio of the gated thyristor means; output means coupled to said first and said second means for producing an output signal when both the armature current and the average conductivity exceed predetermined values; and means coupling said output signal to said control means for changing the mark-space ratio of the gated thyristor means.

Claim 15

In a control circuit including gated thyristor means for metering power to a DC motor having an armature and a field winding, means for controlling the amount of power so metered during motor braking comprising: control means for gating the thyristor means to effect a predetermined mark-space ratio; first means adapted to be coupled to the armature for producing a signal indicative of the current flowing therethrough; second means producing a signal indicative of the mark-space ratio of the gated thyristor means; output means coupled to said first and said second means for producing an output signal when both the armature current and the average conductivity exceed predetermined values; and means coupling said output signal to said control means for changing the mark-space ratio of the gated thyristor means.

Claim 16

The invention defined in claim 10, wherein the gated thyristor means is an SCR.

Claim 17

The invention efined in claim 11, wherein said control means is a voltage-controlled oscillator.

Claim 18

The invention defined in claim 12, wherein said means for producing a signal indicative of armature current comprises a current shunt.

Claim 19

In a control system for a direct current motor having an armature and a field winding, comprising a switchable thyristor device adapted to be coupled between the motor and a source of direct current power and control means for controlling the mark-space conduction ratio of the thyristor device; means for producing a first signal representative of the magnitude of current through the motor armature; means for producing a second signal representative of the average voltage applied to the motor by the thyristor device; means for limiting the mark-space ratio of said thyristor device to a predetermined value; and means for energizing said last-named means when said first and said second signal exceed first and second reference values, respectively.

Claim 20

In a control system for a direct current motor having an armature and a field winding, comprising a switchable thyristor device adapted to be coupled between the motor and a source of direct current power and control means for controlling the mark-space conduction ratio of the thyristor device; means for producing a first signal representative of the magnitude of current through the motor armature; means for producing a second signal representative of the average voltage applied to the motor by the thyristor device; means for limiting the mark-space ratio of said thyristor device to a predetermined value; and means for energizing said last-named means when said first and said second signal exceed first and second reference values, respectively.

Claim 21

In a direct current motor control system for coupling a direct current motor including an armature and a field winding across a source of direct current power, and including a gated semiconductor switch and an oscillator circuit for controlling the mark-space ratio of the switch; first output means for providing a first output signal proportional to armature current; second output means for providing a second output signal proportional to the average voltage applied across the motor; current limit means for comparing said first signal with a reference and outputting a current limit signal when said first signal exceeds said reference; braking signal means coupled to said first and said second output means for producing a braking signal when said first and said second output signals exceed predetermined reference values; and means coupled to said current limit means and said braking signal means and responsive to said current limit signal or said braking signal for limiting the mark-space ratio of the gated semiconductor switch to a predetermined maximum value.

Claim 22

In a direct current motor control system for coupling a direct current motor including an armature and a field winding across a source of direct current power, and including a gated semiconductor switch and an oscillator circuit for controlling the mark-space ratio of the switch; first output means for providing a first output signal proportional to armature current; second output means for providing a second output signal proportional to the average voltage applied across the motor; current limit means for comparing said first signal with a reference and outputting a current limit signal when said first signal exceeds said reference; braking signal means coupled to said first and said second output means for producing a braking signal when said first and said second output signals exceed predetermined reference values; and means coupled to said current limit means and said braking signal means and responsive to said current limit signal or said braking signal for limiting the mark-space ratio of the gated semiconductor switch to a predetermined maximum value.

Claim 23

The invention defined in claim 15, further including means coupled to said current limit means and to said braking signal means for changing the effective value of said current limit means reference when said second output signal exceeds a predetermined value.

Claim 24

The invention defined in claim 16, wherein said gated semiconductor switch is an SCR.

Claim 25

The invention defined in claim 17, wherein said first output means includes a resistive current shunt coupled in circuit with the motor armature.

Claim 26

The invention defined in claim 18, wherein said current limit means reference signal is changed from a first, lower value to a second, higher value in the presence of said second output signal.