Direct current control circuit

Claim 2

A circuit for controlling the amount of power delivered to a load from direct current power source connectable in series with said load comprising: first solid state switching means in series with said load and said source, said switching means alternately changed between a conductive and a nonconductive state to thereby control the effective power applied to said load; storage means for the retention of a quantum of electrical energy in communication with said source whereby said storage means is electrically charged in a first direction; a reversing circuit loop including an inductance and a second solid state switching device each in series with said storage means whereby said storage means may electrically charge in a direction reverse to that first specified independently of said first solid state switching means; a second circuit loop including the storage means, said first solid state switching means and a third solid state switching means; means for placing the third switching means in the conductive state whereby the reverse charge of the storage means will drive said first switching device into a nonconductive state; and additional means including a resistive element connecting said capacitor in series with said source whereby said capacitor may charge and discharge independently of the conductive state of any of said solid state switching devices.

Claim 3

A circuit in accordance with the provisions of claim 1 in which said first, second and third solid state switching means are thyristors.

Claim 4

A circuit in accordance with the provisions of claim 1 in which said load is comprised of a direct current motor.

Claim 5

A circuit in accordance with the provisions of claim 2 in which said load is comprised of a direct current motor.

Claim 6

A circuit in accordance with the provisions of claim 1 further including means operable to selectively switch each of said first, second and third switching means between a conductive and a nonconductive state.

Claim 7

A circuit for controlling the amount of power delivered to a load from source of substantially constant direct current voltage comprising: a series circuit including said source, said load, a first transformer winding and a first solid state switching device, said first device serving to control the effective power supplied to said load by varying the amount of time said series circuit is conductive; means to render said first device conductive; a commutation circuit comprising a series arrangement of a capacitor and a second solid state switching device, said commutation circuit connected in parallel with said first solid state switching device; means including a resistive element providing a path of communication between said source and said capacitor whereby the capacitor may charge and discharge independently of the conductive state of a switching device; and a reversing circuit including a second transformer winding in series with a third solid state switching device, said reversing circuit connected in parallel with said capacitor whereby said capacitor may be charged in a direction to commutate said first solid state switching device.

Claim 8

A circuit for controlling the amount of power delivered to a load from source of substantially constant direct current voltage comprising: a series circuit including said source, said load, a first transformer winding and a first solid state switching device, said first device serving to control the effective power supplied to said load by varying the amount of time said series circuit is conductive; means to render said first device conductive; a commutation circuit comprising a series arrangement of a capacitor and a second solid state switching device, said commutation circuit connected in parallel with said first solid state switching device; means including a resistive element providing a path of communication between said source and said capacitor whereby the capacitor may charge and discharge independently of the conductive state of a switching device; and a reversing circuit including a second transformer winding in series with a third solid state switching device, said reversing circuit connected in parallel with said capacitor whereby said capacitor may be charged in a direction to commutate said first solid state switching device.

Claim 9

A circuit in accordance with the provisions of claim 6 in which said first, second and thirD solid state switching devices are thyristors.

Claim 10

A circuit in accordance with the provisions of claim 6 in which said load is a direct current motor having a series field winding.

Claim 11

A circuit in accordance with the provisions of claim 7 in which said load is a direct current motor having a series field winding.

Claim 12

A circuit in accordance with the provisions of claim 6 in which the means rendering said first device conductive also serves to render said second and third devices conductive.

Claim 13

A control circuit for varying the effective power supplied to a load from a source of substantially constant direct current voltage, said circuit comprising: a first circuit loop including the series arrangement of said source, said load, a first transformer winding and a first solid state switching device selectively variable between a conductive state and a nonconductive state to deliver power from said source to said load in proportion to the amount of time said first solid state switching device is conductive; means including a pulse generator to supply a gating signal to said first switching means to place said first switching means into its conductive state; a second circuit loop comprising a second solid state switching device and a capacitor in series therewith, said second circuit loop connected in parallel with said first solid state switching device; a third circuit loop including a second transformer winding and a third solid state switching device connected in series, said third circuit loop connected in parallel with said capacitor; and additional means including a resistive element connecting said capacitor in series with said source whereby said capacitor may charge and discharge independently of the conductive state of any of said solid state switching devices.

Claim 14

A control circuit for varying the effective power supplied to a load from a source of substantially constant direct current voltage, said circuit comprising: a first circuit loop including the series arrangement of said source, said load, a first transformer winding and a first solid state switching device selectively variable between a conductive state and a nonconductive state to deliver power from said source to said load in proportion to the amount of time said first solid state switching device is conductive; means including a pulse generator to supply a gating signal to said first switching means to place said first switching means into its conductive state; a second circuit loop comprising a second solid state switching device and a capacitor in series therewith, said second circuit loop connected in parallel with said first solid state switching device; a third circuit loop including a second transformer winding and a third solid state switching device connected in series, said third circuit loop connected in parallel with said capacitor; and additional means including a resistive element connecting said capacitor in series with said source whereby said capacitor may charge and discharge independently of the conductive state of any of said solid state switching devices.

Claim 15

A circuit in accordance with the provisions of claim 11 in which said first, second and third solid state switching devices are thyristors.

Claim 16

A circuit in accordance with the provisions of claim 11 in which said load is comprised of a direct current motor.

Claim 17

A circuit in accordance with the provisions of claim 12 in which said load is comprised of a direct current motor.

Claim 18

A circuit in accordance with the provisions of claim 11 in which the second and third switching devices are variable between a conductive and a nonconductive state and in which said pulse generator also serves to supply respective signals to render said second and third devices conductive.

Claim 19

In a battery powered electrical vehicle driven by a direct current motor, a circuit for controlling the amount of power supplied to said motor comprising: a main power circuit including a battery, the motor, a transformer primary winding and a first thyristor all in series; a source of variable frequency pulses for supplying signals to said first thyristor whereby said thyristor may switch from a blocking to a conducting state; a commutating circuit comprising a series arrangement of a second thyristor and a commutating capacitor, said commutating circuit connected in parallel with said first thyristor; resistive means connecting said capacitor in series with said battery whereby an initial charging of said capacitor in a first direction is assured; a reversing circuit including a transformer secondary and a third thyristor in series with said secondary, said reversing circuit connected in parallel with said capacitor; means connecting said source with said third thyristor whereby pulses derived from said source may render said third thyristor conductive to effect the charging of said capacitor in a second direction opposite to that first imposed; and means responsive to a prescribed voltage across said transformer secondary to produce a signal to switch said third thyristor into a conductive state completing a circuit loop comprising said first and second thyristors and said capacitor whereby the second direction charge on said capacitor serves to render said first thyristor nonconductive.

Claim 20

In a battery powered electrical vehicle driven by a direct current motor, a circuit for controlling the amount of power supplied to said motor comprising: a main power circuit including a battery, the motor, a transformer primary winding and a first thyristor all in series; a source of variable frequency pulses for supplying signals to said first thyristor whereby said thyristor may switch from a blocking to a conducting state; a commutating circuit comprising a series arrangement of a second thyristor and a commutating capacitor, said commutating circuit connected in parallel with said first thyristor; resistive means connecting said capacitor in series with said battery whereby an initial charging of said capacitor in a first direction is assured; a reversing circuit including a transformer secondary and a third thyristor in series with said secondary, said reversing circuit connected in parallel with said capacitor; means connecting said source with said third thyristor whereby pulses derived from said source may render said third thyristor conductive to effect the charging of said capacitor in a second direction opposite to that first imposed; and means responsive to a prescribed voltage across said transformer secondary to produce a signal to switch said third thyristor into a conductive state completing a circuit loop comprising said first and second thyristors and said capacitor whereby the second direction charge on said capacitor serves to render said first thyristor nonconductive.

Claim 21

The inventiOn in accordance with the provisions of claim 16 in which said motor includes an armature winding and a series field winding and further including means selectively operable to reverse the relative direction of current with said armature and field windings.

Claim 22

The invention in accordance with the provisions of claim 16 further including means to provide dynamic braking to said motor.

Claim 23

The invention in accordance with the provisions of claim 17 in which the primary and secondary transformer windings are separated and directly coupled by inductive effect only.