D-C motor drive system with field current flow reversal upon transition between motoring and retarding modes

• US 4,054,821 A
• Filed: 12/18/1975
• Issued: 10/18/1977
• Est. Priority Date: 08/30/1974
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Williamson, Dennis Francis
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Feldhaus, John J.
• Application Number:
  US05/641,846
• Time in Patent Office: 670 Days
• Field of Search: 318/375, 318/376, 318/379, 318/380, 318/381, 318/505, 318/506, 318/507, 318/247, 318/248
• US Class Current: 318/375
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 7/22 Dynamic electric resistor braking, combined with dynamic electric regenerative braking
• CPC Class Codes: H02P 7/281 the DC motor being operated in four quadrants
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility

Abstract

A d-c motor drive system, useful for propelling and retarding electrically propelled traction vehicles, wherein the armature winding has a first terminal coupled through an armature chopper to a first polarity conductor of a d-c source, and a second terminal coupled through a breaker switch to a second polarity conductor of the d-c source. First and second controlled rectifiers are connected across the first and second conductors in a self commutating circuit such that they conduct sequentially and alternatively. Means are provided for varying their respective conduction time intervals to control the voltage at their junction. Field winding means are coupled from the junction of the controlled rectifiers to the junction of the armature second terminal and the breaker. During the motoring mode with the breaker closed field current flows in a first direction. During the retarding mode with breaker open and the second terminal of the armature coupled by a diode to the first conductor, field current flows in an opposite direction to permit d-c motor to operate as a retarding generator.

Claims

1. In a drive system for d-c motors, comprising armature and field means, coupled to drive a mechanical load during a motoring mode and to be driven by said load during a retarding mode, and wherein during said motoring mode said armature means are coupled between first polarity and second polarity conductors adapted to be connected to a d-c source and during the retarding mode the direction of current through said field means is reversed and the armature means are coupled to supply a circuit for dissipating generated armature current, the combination comprising:

a. said first and second conductors;

b. said armature means comprising first and second terminals, said first terminal adapted to be coupled through armature impedance means to said first conductor;

breaker switch means adapted to be open during the retarding mode and closed during the motoring mode, connected between said second terminal and said second conductor;

d. conductive means conductive solely during the retarding mode connected from said second terminal to said first conductor.

e. first and second impedance means coupled between said first and second conductors and at their junction providing a controllable voltage output terminal;

f. said field means being coupled between said voltage output terminal and said second terminal so that field current flows in a first direction during the motoring mode and in a second direction during the retarding mode.

2. The arrangement of claim 1 wherein said first and second impedance means each comprise switching means adapted to be sequentially and alternately conducting.

3. The arrangement of claim 2 comprising means for varying the conduction time of one of said switching means in respect to that of the other switching means for controlling the average potential at the controllable output terminal.

4. The arrangement of claim 3 wherein said conductive means comprises unilaterally conducting means poled to conduct generated armature current during the retarding mode.

5. The arrangement of claim 4 wherein said armature impedance means comprises chopper switching means.

6. The arrangement of claim 5 wherein said first and second switching means comprise controlled rectifiers connected in a self commutating back-to-back chopper circuit.

7. The arrangement of claim 6 wherein unilaterally conducting means are coupled from said second conductor to said first terminal of the armature means.

8. The arrangement of claim 2 wherein capacitance means are coupled across said first and second conductors.

9. The arrangement of claim 2 wherein means for boosting current through said field means in the retarding mode direction comprise a source of potential and unidirectionally conducting means coupled in series circuit with said field means, said unidirectionally conducting means being poled to conduct current from said source of potential through said field means in the retarding mode direction.

10. In a drive system for d-c motor means coupled to a mechanical load, said motor means comprising armature means and separately excited field means and being effective with said mechanical load moving in a given direction to drive the load in a motoring mode and to be driven by the load in a retarding mode, said armature means being coupled through armature impedance means to a d-c source having a pair of conductors at different potentials, the improvement comprising:

a. first and second impedance means connected in series with one another between said conductors for providing at an output terminal coupled to their junction a controllable field voltage;

b. means for controlling said first and second impedance means so as to vary as desired, within a range defined by the respective potentials on said conductors, the average magnitude of voltage at said output terminal;

c. switch means having a pair of terminals and adapted to be open during said retarding mode and closed during said motoring mode, one of said terminals being connected to a first one of said pair of conductors;

d. conductive means for connecting the other terminal of said switch means to the other one of said conductors, said conductive means being conductive solely when said switch means is open;

e. means for coupling said field means between said field voltage output terminal and said other terminal of said switch means, whereby field current flows between said output terminal and said other terminal in one direction when said switch means is closed during said motoring mode and in the opposite direction when said switch means is open and said conductive means is conductive during said retarding mode; and

f. means for connecting said other terminal of said switch means to said armature means, whereby said switch means is included in the coupling between said armature means and said d-c source during said motoring mode.

11. The improvement of claim 10 wherein said first and second impedance means comprise switching means adapted to be sequentially and alternately conducting.

12. The improvement of claim 10 wherein said conductive means comprises a rectifier poled to block current when said other terminal has substantially the same potential as said first one of said conductors due to said switch means being closed.

13. The improvement of claim 10 further comprising means for controllably boosting current through said field means in said retarding mode direction.

14. The improvement of claim 10 further comprising a capacitor connected across said conductors.