Title of Invention

"SCHEME FOR ELECTRIC VEHICLE PROPULSION USING ALTERNATING CURRENT TRACTION".

Abstract

The present invention relates to a Device for electric vehicle propulsion using alternating current traction comprising: a means to supply Power to the vehicle (la to Id), a power controller(3) to supply controlled power an input signal transducer (4)to control the power controller, an output monitoring means built in the power controller (4) a traction motor (6) to receive the power from power controller, a torque transmission means connected with the traction motor (6) and a means to act as a safety equipment connected to the power controller

Full Text

The present invention relates to a Device for electric vehicle propulsion using alternating current traction . More particularly the invention relates to a scheme for electric vehicle propulsion using alternating current traction. In the known state of the art, either internal combustion engines or Direct current motors are used for all vehicular propulsion - and both these methods suffer from various drawbacks explained below. It is well established that internal combustion engines used on all motor vehicles currently, suffer from a technological limit beyond which their efficiency can not be improved. Useful power is obtained only from the volumetric expansion of the combustion product gases but all the heat generated is lost forever, to entropy. A diesel engine's maximum achievable thermal efficiency with turbo charging and pre - heating, is about 40%. A petrol engine (or CNG or IPG engine, since they are basically identical), despite all the improvements made recently in terms of computer controlled direct fuel injection (MPFI) can not be made more thermal efficient than about 25%. The useful power assumed to have been obtained even at such a low thermal efficiency is actually not available to the user. Power is generated by reciprocal action of the pistons, whereas almost all useful power is required in rotary form. The conversion of power from reciprocal motion to rotary motion, using a crankshaft, connecting rods, big-end and small-end journal bearings etc. is extremely wasteful. Almost a fifth of the engine power turns into heat in making this conversion. This heat and unavoidable reciprocal action acts directly on the above mentioned components, making them most susceptible to failure. All the systems based on direct current (D.C.) technology, use a very large capacity D.C. motor coupled directly to the driven wheels through a fixed gear ratio. This technology, while being simpler to adopt suffers from disadvantages, which are listed below. I. All large D.C. motors re/yon the principle of commutation. The commutator consists of an insulating hub mounted on the rotor shaft behind the winding. Equally spaced strips of copper are mounted all around this hub and connected to the rotor windings. Two or more carbon brushes constantly rub against these commutator strips and transfer electricity to the rotor windings. These carbon brushes wear out fast due to the combined effect of abrasion and high current conduction and have to be replaced very frequently. If worn brushes are not detected in time the brush holder, which is metallic, comes into direct contact with the copper strips and tears them out of the commutator hub. 2. Conventional D.C, traction control systems involve some form of interruption of electrical power delivery to the motor with a rapidity determined by a signal voltage from a remotely operated device like a foot pedal potentiometer. The problem.with any'make'or'break' of a high current D.C. circuit is the generation of ' transients'(Ldi/dt). particularly with highly inductive loads which motor windings present. These transients give rise to very large inverse, voltages which play havoc with the circuitry. 3. A vehicle requires a high torque delivery at starting from rest and also at low speeds. This aspect is commonly referred to as the 'pick up' of a vehicle. Most electromotors suffer, in comparison to engines, in this department. To overcome this handicap the conventional system is to use a very large H.P. motor, almost two and half times bigger than the engine would have been for an equivalent vehicle. A large motor involves handling of very high starting currents and forces an upgrading of the entire control circuitry just for a brief requirement of high current at start. 4. Another problem is with D.C. generation and transmission. D.C. power is no longer generated in power stations in India. Further D.C. power is very difficult to step up or step down, unlike A.C. power. It also suffers a lot of loss in transmission at useful voltages due to 'skin effect' of the conductors. It is the object of this invention to provide conceptual technology for running an electric vehicle using alternating current. This technology can be used to manufacture new electric vehicles and more importantly, can be retro-fitted on existing internal combustion run vehicles. It is also the object of this invention to provide the means of an energy efficient, economical, non polluting solution for public transport. The design is composed of the following systems, each of which shall be better understood by referring to. the general arrangement drawing provided. 1. The power source. 2. The power collection system. 3. The power controller. 4. Input signal transducer. 5. Output monitoring systems. 6. Traction motor. 7. Torque transmission. 8. Supervisory and safety equipment. 1. Power to run-the vehicle can either be obtained by:- (a) Batteries and suitable inverter to produce A.C. power. These batteries can be either 'on board' or preferably in the form of a separately charge-able, replaceable power pock mounted on a trolley and towed behind the vehicle. (b) A small generator run at constant r.p.m. on the least polluting fuel available. This again can either be 'on board' or towed as above. It has been experimentally proved that an engine running at constant rpm as in a generator consumes less than one third the fuel and emits less than one fourth the pollutants that the same, engine if used in the vehicular mode and subjected to frequent speed changes and frequent variations in torque and power requirements, would. c) A balanced hybrid of batteries and generator (as above described), either accommodated 'on board' or towed behind the vehicle. (d) Four conductor, 3 phase and earth, overhead AC transmission. The conductors would be insulated and shrouded for safety. The conductor system would facilitate multi point feeding of power along the route and would incorporate insulated sections periodically. The power supply used would be the standard 415 volts available in India. This system would be ideally suited for public buses traveling on fixed routes. 2. The power collection System ;--(α) For a towed power pack, it would be a simple flexible cable attached by plugs and sockets to the vehicle and the trolley. .b) The shrouded overhead conductor system incorporates sliding current collector trolleys. These trolleys ride on insulated wheels on the edges of the overhead channel. Current collecting shoes slide on the four conductors embedded in the channel and the power so collected can be routed to the vehicle using cables and a collecting arm. A plug and socket system would couple the sliding trolley to the vehicle. In addition a chain or collecting arm would mechanically drag the sliding trolley behind the vehicle. The mechanism as well as the plug and socket would have feature which would make them get detached from the conductor channel if the vehicle happens to stray too much from its designated line of travel. 3. The Power controller The ideal controller for an AC. motor of any size is a computer controlled I.G.B.T. (Insulated Gate Bipolar Transistor) based drive. These drives, while providing a host of protective services to the motor, achieve the desired motor speed and torque by providing a computer determined mix of frequency and voltage to the motor. The computer calculates this mix on the basis of the input signal provided to it from a remote transducer. 4. The input signal transducer The purpose of the input signal transducer ,as mentioned above, is to' provide the drive computer with an analog or digital signal, either in proportion to a voltage or current generated due to a remote activity of the vehicle driver. In its simplest form, such a transducer would be film or wire wound potentiometer or any other kind of device, attached mechanically to the driver's accelerator pedal. For example, depression of the accelerator would cause the resistance value of the potentiometer to change. A reference voltage when placed across the 'pot's terminals would show a corresponding change at the slider tap. 5. Output monitoring Systems Measurements of the following parameters need to be available for an electric vehicle's satisfactory operation : (a) I/P and O/P volts. (b) I/P and O/P currents. (c) I/P and O/P frequency. (d) Torque developed by the motor. (e) Motor R.P.M. (f) Duration of usage. Most of these functions can be fulfilled by the drive computer mentioned above . 6. The traction motor The traction motor selected for this system is a standard 3 phase squirrel cage induction motor. This kind of motor is universally acknowledged as the most robust, maintenance free, pollution free, low noise and economical motor ever invented by man. This kind of motor has no commutators, no slip rings, no carbon brushes and no sliding contacts. It is easily available in all sizes possibly required for vehicle use and requires no maintenance during its almost infinite designed life. Experiments have shown that the minimum sufficient capacity of the motor is close to about half the engine horse power one would have selected for a similar road vehicle. It would be sensible to minimise the size of the motor because it translates to savings in the amount of power consumed. This is particularly important for battery based and hybrid vehicles. 7. Toroue transmission Conventional torque transmission systems, of the D.C. traction variety, utilised very large capacity motors, rotating a gear set of fixed ratio, directly coupled to the driving wheels. In this design, it has been chosen to couple a small traction motor, through a clutch, to a variable ratio gearbox. (Use of a fluid coupling and centrifugal gearbox is also a practical but more expensive possibility). The gearbox in turn transfers the torque to a propeller shaft (in the case of rear wheel drive) which reaches the driving wheels through a fixed ratio gearbox or direction changing differential gearbox.The variable ratio gearbox acts as a torque converter. By selectively sacrificing speed, even a small motor is made capable of delivering the desired torque at start and low speeds. Further, by incorporating a clutch (or slip) assembly, it is possible to keep the motor 'idling', even when the vehicle is at rest. The biggest benefit of this innovation is that the motor is never 'started' on full load. This eliminates high starting currents from the system altogether. The vehicle can accelerate smoothly from rest, without a starting jerk as experienced on a Mumbai suburban train. 8. Safety equipment It will be appreciated that since the motor is being operated on a 3 phase ,415 volt supply, the safety hazards faced, are the some as encountered in domestic or industrial wiring. Consequently, for the non-overhead systems of power supply for electric vehicles, the standard safety protocol specified in the Indian Electricity rules should be adhered to. An additional earth fault monitoring system should be installed to ensure the tripping of the power supply in case of phase to body leakage in any of the power devices. The overhead conductor system already caters for an earth conductor, grounded at various points along the route, in accordance with earthing rules. However, an onboard, additional earth fault monitor will only serve to enhance passenger safety further. An input supply surge protecting circuit is advisable, though unlike D.C. transmission, it is not essential for this A.C. system. The I.&.B. T. drive employed for motor control, already incorporates input filters and S.M.P.S. for its in built computer. STATEMENT OF INVENTION: The present invention relates to a Device for electric vehicle propulsion using alternating current traction comprising: a means to supply Power to the vehicle (la to Id) , a power controller(S) to supply controlled power an input signal transducer (4)to control the power controller, an output monitoring means built in the power controller (4) a traction motor (6) to receive the power from power controller, a torque transmission means connected with the traction motor (6) and a means to act as a safety equipment connected to the power controller I claim ' 1. A Device for electric vehicle propulsion using alternating current traction comprising: a means to supply Power to the vehicle (la to Id), a power controller(3) to supply controlled power an input signal transducer (4)to control the power controller, an output monitoring means built in the power controller (4) a traction motor (6) to receive the power from power controller, a torque transmission means connected with the traction motor (6) and a means to act as a safety equipment connected to the power controller 2. A Device for electric vehicle propulsion as claimed in claim 1 wherein the means to supply Power to the vehicle are (a) Batteries and suitable inverter to produce A.C. power,(b) A small generator run at constant r.p.m. on the least polluting fuel available,(c) A balanced hybrid of batteries and generator,(d) Four insulated conductors ,3 phase and earth, overhead A.C. transmission. 3. A Device for electric vehicle propulsion as claimed in claim 1 wherein a means for the power collection are (a) a flexible cable attached by plugs and sockets to the vehicle and the trolley (b) the shrouded overhead conductor system incorporating sliding current collector trolley riding on insulated wheels on the edges of the overhead channel. 4. A Device for electric vehicle propulsion as claimed in claim 1 wherein the power controller is a computer controlled Insulated Gate Bipolar Transistor based drive. 5. A Device for electric vehicle propulsion as claimed in claim 1 wherein input signal transducer is a film or wire wound potentiometer or any other kind of device, attached mechanically to the driver's accelerator pedal. 6. A Device for electric vehicle propulsion as claimed in claim 1 wherein an output monitoring means is any conventional means used for measurements of the T/P-and 0/Pcurrents, I/P and 0/P frequency, Torque developed by the motor. Motor RP:M, Duration of usage etc. 7. A Device for electric vehicle propulsion as claimed in claim 1 wherein the traction motor is selected from a standard 3-phase squirrel cage induction motor. 8. A Device for electric vehicle propulsion as claimed in claim 1 wherein the torque transmission is a_ small traction motor, coupled through a clutch, to a variable ratio gearbox, 9. A Device for electric vehicle propulsion as claimed in claim 1 wherein the means to act as a safety equipment are an additional earth fault monitoring system to install to ensure the tripping of the power supply in case of phase to body leakage in any of the power devices 10. A Device for electric vehicle propulsion such as hereinbefore described with reference to the drawings.

Documents:

950-del-2000-abstract.pdf

950-del-2000-claims.pdf

950-del-2000-correspondence-others.pdf

950-del-2000-correspondence-po.pdf

950-del-2000-description (complete).pdf

950-del-2000-drawings.pdf

950-del-2000-form-1.pdf

950-del-2000-form-18.pdf

950-del-2000-form-2.pdf

950-del-2000-form-3.pdf