Propulsion and electric braking system for electric traction motor vehicle

• US 5,323,095 A
• Filed: 04/30/1991
• Issued: 06/21/1994
• Est. Priority Date: 04/30/1991
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Kumar, Ajith K.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): MARTIN, DAVID S
• Application Number:
  US07/693,743
• Time in Patent Office: 1,148 Days
• Field of Search: 388/800-808, 388/907.2, 388/917-920, 318/139, 318/370, 318/375-381, 318/798-803, 318/758-759, 318/53, 318/60, 318/69, 318/59, 318/66, 318/68, 318/80, 318/71, 318/79, 318/89, 318/151-154
• US Class Current: 318/376
• CPC Class Codes: B60L 7/04 for vehicles propelled by dc motors
• CPC Class Codes: B60L 7/22 Dynamic electric resistor braking, combined with dynamic electric regenerative braking
• CPC Class Codes: Y10S 388/917 Thyristor or scr

Abstract

A system and method for controlling power transfer between an internal combustion driven electrical power generator and a direct current (DC) motor. In one form, the invention includes control of a power inverter in a manner to restrict current through a winding of the generator to a predetermined polarity. The inverter includes a plurality of gate controlled switching devices which are selectively energized to allow current to free wheel through the motor during at least some portion of each alternating voltage cycle of the generator. In another form, a plurality of resistors are connected in series with an inverter and a DC motor with each resistor including a switching device for bypassing current around the associated resistor. In this form, resistors can be selectively inserted into the series path during electrical braking so that a maximum amount of electrical energy can be transferred to the generator through the inverter without exceeding the voltage limits of the inverter during high speed braking. Regenerative braking is further maximized during low speed or reduced braking requirements by removing resistors from the series current path.

Claims

1. A system for regenerative and dynamic electrical braking of an electrically powered traction vehicle, the vehicle including an alternating current (AC) power source connected to be driven by an internal combustion engine, a full wave controlled rectifier bridge circuit connected to electrical power output terminals of the power source for converting the output AC power to unidirectional current (DC) power, and at least one DC motor having an armature connected in electrical circuit with the rectifier bridge circuit, the system comprising:

dynamic braking resistance means operatively connected in series electrical circuit between the DC motor armature and the rectifier bridge circuit; and

switching means, operatively connected in parallel circuit arrangement with the resistance means, for selectively controlling introduction of the resistance means into the series electrical circuit, the electrical energy developed by the DC motor armature during electrical braking of the vehicle being selectively divided between regenerative and dynamic braking by control of the switching means.

2. The system of claim 1 wherein the resistance means comprises:

a plurality of serially connected resistive elements; and

the switching means comprises;

a plurality of separately controllable switching devices, each of the switching devices being connected in parallel circuit arrangement with a respective one of the resistive elements, the value of the resistance means being variable between minimum and maximum values by selectively energizing each of the switching devices to maximize the available amount of electrical energy transferable from the electric motor to the power source.

3. The system of claim 2 wherein the full wave controlled rectifier bridge circuit electrically interconnects a winding of the AC power source into a current supplying circuit with a field winding of the at least one DC motor.

4. The system of claim 3 further comprising:

control means connected to supply gating signals to the bridge circuit for selectively energizing controlled rectifiers therein in a manner to regulate the armature current generated by the motor in an electrical braking mode, the gating signals being applied to gate a first pair of rectifiers into conduction for coupling the AC source winding into circuit with the motor field winding for establishing a first preselected magnitude of current in the motor field winding, the gating signals thereafter being applied to another pair of the rectifiers such that the motor field winding current bypasses the AC source winding, the control means continuing to apply the gating signals to selected pairs of the controlled rectifiers such that the AC source winding is connected to the motor field winding only during intervals in which the polarity of voltage generated by the AC source winding is a preselected polarity.

6. The method of claim 1 further comprising the steps of:

gating a third pair of the controlled rectifiers into conduction in a series current path with the motor field winding and generator winding such that current produced by the generator winding is forced through the motor field winding in the first preselected direction; and

gating a fourth pair of rectifiers into conduction when the generator winding voltage changes to the first preselected polarity to shunt motor field winding current into another circulating current path bypassing the generator winding.

7. The method of claim 6 wherein the bridge circuit includes at least eight controlled rectifiers, at least four of the at least eight rectifiers forming a first group poled to conduct current in a first direction through the DC load and at least another four of the at least eight rectifiers forming a second group poled to conduct current in a second direction through the DC load, said step of selecting the gating of the controlled rectifiers to establish a predetermined polarity of current comprising the step of selectively gating into conduction the controlled rectifiers in one of said first and second groups for controlling the direction of current through the DC load.

5. A method for reducing ripple currents in a winding of an alternating current (AC) power generator connected in electrical circuit with a full wave controlled rectifier bridge circuit, output terminals of the bridge circuit being connected to supply unidirectional current (DC) to a field winding of an electric motor, control means coupled to the controlled rectifiers for selectively gating the rectifiers into conduction in a manner to regulate the polarity and magnitude of DC current in the field winding of the motor to preselected values, the method comprising the steps of:

gating a first pair of the rectifiers into conduction to couple the generator winding into series circuit with the motor field winding during a time period when the polarity of voltage developed by the generator winding is at a first preselected polarity for forcing current in a first preselected direction through the motor field winding; and

gating a second pair of the rectifiers into conduction to shunt motor field winding current into a circulating current path bypassing the generator winding when the polarity of voltage developed by the generator winding is reversed from the first preselected polarity.

8. A method for operating a full wave controlled rectifier alternating current (AC) to direct current (DC) power bridge circuit for minimizing ripple currents in a DC load, the bridge circuit including at least four controlled rectifiers for selectively coupling an AC source to the DC load in a manner to regulate load current through the DC load to a preselected value, the method comprising the steps of:

(a) gating a series combination of at least two controlled rectifiers into conduction for circulating load current through the DC load in a current path bypassing the AC source;

(b) selectively gating another of the controlled rectifiers into conduction for establishing a current path through the AC source for the load current;

(c) gating still another of the controlled rectifiers into conduction in series with the another of the controlled rectifiers for bypassing load current about the AC source when the AC source changes voltage polarity; and

(d) alternately repeating the steps of selectively gating and gating still another of the controlled rectifiers at preselected times for regulating the DC load current to the preselected value.

9. The method of claim 8 further comprising the step of:

effecting a reduction in the RMS current through the AC source by shunting load current about the AC source during at least one half cycle of operation of the AC source.

10. The method of claim 9 further comprising the step of:

selecting the gating of the controlled rectifiers to establish a predetermined polarity of current through the DC load.

11. The method of claim 10 wherein the bridge circuit includes at least eight controlled rectifiers, at least four of the at least eight rectifiers forming a first group poled to conduct current in a first direction through the DC load and at least another four of the at least eight rectifiers forming a second group poled to conduct current in a second direction through the DC load, said step of selecting the gating of the controlled rectifiers to establish a predetermined polarity of current comprising the step of selectively gating into conduction the controlled rectifiers in one of said first and second groups for controlling the direction of current through the Dc load.