SYSTEM FOR BLENDING REGENERATIVE AND DYNAMIC AND FRICTION BRAKING

• US 3,774,095 A
• Filed: 09/20/1972
• Issued: 11/20/1973
• Est. Priority Date: 09/20/1972
• Status: Expired due to Term

• Current Assignee: Westinghouse Air Brake Co (Westinghouse Air Brake Technologies Corporation)
• Original Assignee: Rudolph A. Coccia
• Inventors: Coccia, Rudolph A.
• Primary Examiner(s): Gilheany, Bernard A.
• Assistant Examiner(s): Duncanson, Jr., W. E.
• Application Number:
  US05/290,480
• Time in Patent Office: 426 Days
• Field of Search: 318/139,274,364-366,370,371,376
• US Class Current: 318/371
• CPC Class Codes: H02P 3/26 by combined electrical and mechanical braking

Abstract

A brake control system for a railway vehicle having an a. c. inverter drive for an induction type motor capable of being operated in a regenerative mode to effect vehicle retardation by either supplying current flow to the system supply source (regenerative braking) for use by other vehicles operating in a power mode or by dissipating the current flow in the form of heat at resistive grids (dynamic braking). The system is normally conditioned so that regenerative braking provides the primary source of vehicle retardation with the torque effort produced being compared with the brake or torque command to effect a friction brake application in accordance with the difference therebetween. The friction brake thus supplements the regenerative brake up to a predetermined point at which it is desired to establish dynamic braking. Once the dynamic brake applies, the combined regenerative and dynamic brake effectiveness results in the torque effort being increased so that the difference between torque effort and torque command is reduced and accordingly the friction brake is released proportionately, thereby providing for combining the friction, dynamic and regenerative brakes, or any combination thereof, in an attempt to provide and maintain a constant rate of deceleration irrespective of variable conditions affecting the degree of regenerative and dynamic braking available.

Claims

1. A brake control system for a railway vehicle driven by a traction motor, comprising in combination:

a. circuit means for connecting said traction motor with a source of supply voltage and an ohmic load in parallel, and including a normally open switch intermediate said ohmic load and said motor whereby said motor is effective to supply power to said voltage source when operating in a regenerative mode, b. means for controlling the degree of regeneration of said motor in accordance with a brake command signal, c. means for sensing the torque produced by said motor to provide a brake effect signal corresponding to the level of power flow generated by said motor, d. friction brake control means for providing friction braking in accordance with the difference between said brake command signal and said brake effort signal to supplement the regenerative action of said motor in obtaining the desired level of retardation of said vehicle when said source of supply voltage is non-receptive to regenerative power, and e. means for effecting operation of said switch means to connect said ohmic load with said motor at a predetermined level of said friction brake to provide for a level of regenerative power flow from said motor corresponding to said brake command signal.

2. The system, as recited in claim 1, further comprising lockup means for maintaining said ohmic load connected with said motor irrespective of a subsequent reduction of said friction brake application below said predetermined level in accordance with said increased level of regenerative power flow increasing said brake effort signal.

3. The system, as recited in claim 2, further comprising means for resetting said lockup means in accordance with selective inputs being provided thereto.

4. The system, as recited in claim 3, wherein said lockup means comprises:

a. a relay to which said normally open switch is operatively responsive, and b. a flip-flop having one input connected with said switch controlling means, another input connected with said reset means and an output connected with said relay to effect closure of said switch only when a signal is provided at said one input and absent at said another input.

5. The system, as recited in claim 1, fuRther comprising:

a. first summing means subject to said brake command signal and said brake effort signal for providing an error signal in accordance with the difference therebetween, b. transducer means for providing a feedback signal representative of the level of said friction braking in effect, and c. second summing means subject to said error signal and said feedback signal to provide a friction brake control signal for regulating said friction brake control means.

6. The system, as recited in claim 1, in which:

a. said motor is an a. c. induction motor, b. said source of supply voltage is regulated d. c. power to which other vehicles are dependent for supply voltage, c. said means for controlling the degree of regeneration of said motor includes;

i. first summing means for providing a motor slip control signal in accordance with the difference between said brake command and said brake effort signals effective thereat, ii. speed sensing means for providing a speed signal representative of the speed of rotation of said motor, and iii. second summing means subject to said slip control signal and said speed signal for providing a frequency control signal, and d. said circuit means includes inverter means subject to said frequency control signal for energizing the stator of said motor at a frequency which lags the rotating frequency of the rotor of said motor an amount corresponding to said brake command signal.

7. The system, as recited in claim 6, further comprising:

a. a control wire extending through said vehicle, b. a controller device for effecting variation of current flow in said control wire in accordance with the desired rate of retardation of said vehicle, and c. transducer means connected to said control wire for monitoring the level of current therein to provide said brake command signal as a voltage proportional to current effective in said control wire.

8. The system, as recited in claim 1, wherein said means operable at a predetermined level of said friction brake comprises a threshold detector subject to fluid pressure supplied to brake units in accordance with operation of said brake control means, said threshold detector having a bias signal provided to prevent said detector for providing an output to effect operation of said switch means until said friction brake fluid pressure exceeds said bias signal.

9. The system, as recited in claim 1, wherein said means operable at a predetermined level of said friction brake comprises summing means subject to said brake command signal, said brake effort signal and a bias signal of the same polarity as said brake effort signal and corresponding in value to said predetermined friction brake level to prevent said summing means for providing an output to operate said switch means until the difference between said brake command and said brake effort signals corresponding to said error signal exceeds a value corresponding to said predetermined friction brake level.