Use of SCR's in extended retarding
First Claim
1. In a drive system for a vehicle wherein an alternator driven by a power source produces AC current that is rectified to DC current before being used to power wheel motors and wherein the drive system provides for retarding of the motion of the vehicle by suspension of the DC current from the alternator that is driving the wheel motors and then allowing the wheel motors to generate a DC current that is directed through a series of resistors to dissipate the energy, the specific improvement comprising:
- (a) a first SCR located between the output of the DC current generated by the wheel motors during retarding of the motion of the vehicle and the series of resistors through which the DC current is directed to dissipate the energy;
(b) at least one circuit containing a second SCR wherein said circuit when said second SCR is conductive shunts a portion of the series of resistors through which the DC current generated by the wheel motors is directed; and
(c) at least one circuit containing a third SCR wherein said circuit when said third SCR is conductive delivers current from said alternator to the cathode of said first SCR such as to back bias said first SCR and allow it to be turned off.
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Accused Products
Abstract
An improved drive system for large mining trucks employing combined diesel/electric propulsion or the like wherein AC current generated by the alternator is rectified before powering wheel motors and wherein the wheel motors are used as generators to produce a retarding current that is directed to a resistive grid with plurality of shunting circuits thus extending the retard torque during dynamic braking and deceleration of the vehicle wherein the improvement comprises the use of silicon controlled rectifiers (SCR'"'"'s) rather than contactors to achieve the desired electric circuit arrangement and in particular wherein four SCR'"'"'s are used in the resistive grid to achieve a seven stage extension of the retarding torque and wherein the SCR'"'"'s in the DC circuit are deactivated (opened) by back biasing with an SCR circuit that delivers AC current from the alternator to the cathode of a switching SCR in the retarding circuit.
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Citations
18 Claims
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1. In a drive system for a vehicle wherein an alternator driven by a power source produces AC current that is rectified to DC current before being used to power wheel motors and wherein the drive system provides for retarding of the motion of the vehicle by suspension of the DC current from the alternator that is driving the wheel motors and then allowing the wheel motors to generate a DC current that is directed through a series of resistors to dissipate the energy, the specific improvement comprising:
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(a) a first SCR located between the output of the DC current generated by the wheel motors during retarding of the motion of the vehicle and the series of resistors through which the DC current is directed to dissipate the energy; (b) at least one circuit containing a second SCR wherein said circuit when said second SCR is conductive shunts a portion of the series of resistors through which the DC current generated by the wheel motors is directed; and (c) at least one circuit containing a third SCR wherein said circuit when said third SCR is conductive delivers current from said alternator to the cathode of said first SCR such as to back bias said first SCR and allow it to be turned off. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of operating a drive system of a vehicle wherein an alternator driven by a power source produces AC current that is rectified to DC current before being used to power wheel motors and wherein the drive system provides for retarding of the motion of the vehicle by suspending the DC current from the alternator powering the wheel motors and then allowing the wheel motors to generate a DC current which is directed through a resistive grid to dissipate the energy and thus apply retarding torque decelerating the vehicle in which at least one SCR is located between the output of the DC current generated by the wheel motors during retarding of the motion of the vehicle and the resistive grid through which the DC current is directed to dissipate the energy, and a plurality of shunting circuits is utilized each containing a separate SCR that when conductive shunts a portion of the resistive grid and in which at least one circuit contains a SCR that when conductive delivers AC current from the alternator to the cathode of the at least one SCR located between the output of the DC current generated by the wheel motors and the resistive grid, the method of operating the drive system comprising the steps of:
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(a) activating the SCR in said one circuit that delivers AC current from the alternator to the cathode of the at least one SCR located between the output of the DC current generated by the wheel motors and the resistive grid; (b) deactivating the at least one SCR located between the output of the DC current generated by the wheel motors and the resistive grid; and (c) deactivating the SCR in said one circuit that delivers AC current from the alternator to the cathode of the at least one SCR located between the output of the DC current generated by the wheel motors and the resistive grid, thus allowing further selective activation and deactivation of the SCR'"'"'s of the plurality of shunting circuits.
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Specification