Abstract: Two or more gated type power switches, particularly mosfets, are disclosed in a protection circuit which protects the other power switches should one of them short to its respective gate. The circuit includes elements for sensing the occurrence of the failure, for carrying or diverting excess current from the gates, and increasing the impedance of the gates to minimize any damage. The circuit prevents the failure of one mosfet in a drain to gate short mode from destroying or damaging the other parallel mosfets. The invention results in easier analysis and repair of any damage should a breakdown occur, and for the first time makes practical the use of many mosfets in parallel for power switching applications.

Abstract: A method and apparatus are disclosed for use with a battery powered inverter for powering a load through a ferroresonant transformer. The current flow through the inverter-ferroresorant transformer is sensed and is utilized to modulate the inverter's pulse width at a point, after a peak voltage but before saturation begins, when the slope of the inverter-ferroresonant transformer current with respect to time is at or near zero. A maximum current limiting feature can be provided in the method and apparatus of the present invention.

Abstract: A thermal current limiting controller for use in protecting the electric drive motor, controller and battery of an electrically propelled vehicle against damage thereto resulting from excessive temperature conditions. The controller is arranged to calculate the temperature condition of the motor as a function of the current flow therethrough and more specifically, integrates the current flow with respect to time so as to provide a control signal proportional to the calculated temperature condition. The control signal is utilized to limit the amount of current the drive motor is permitted to draw notwithstanding an attempt by the operator of the vehicle to cause the drive motor to draw greater current. The controller further includes an indicator which is responsive to the control signal to provide a variable indication of the temperature condition so as to warn the vehicle operator of the magnitude of the undesirable heating of the drive motor and, thus, the impairment of the system capabilities.

Abstract: Cooling means for cooling a control such as for use in controlling the operation of electric vehicles or the like. The control utilizes a direct current battery power supply and includes an inverter for delivering alternating current to an alternating current motor of an air moving structure, such as a fan, provided for cooling the control during the operation thereof. The circuit is arranged to cause the fan to have variable power as a direct function of the load demand of the control circuit so that maximum cooling occurs when the load demand in the control is maximum and minimum cooling occurs when the load demand is minimum. The circuit is arranged to maintain an effectively constant volt-second duty cycle characteristic at the control power supply to the air moving structure whereby the variation in power developed by the motor thereof is a function of the duty cycle characteristics of the control power supply as applied to the motor.

Abstract: A universal command signal producing apparatus adapted for use in an electrically operated vehicle. The apparatus includes a rotatable electrical element for use in controlling a drive function of the vehicle, such as a speed control function or a braking function. The apparatus is arranged to act as a transducer between a foot pedal, adapted to be actuated by the user of the vehicle, and the propulsion control to selectively control the electric drive motor of the vehicle or the braking system thereof. The transducer apparatus may include a sprocket associated with the rotatable electrical control device and driven by a chain forming a part of the transducer. The chain may be mounted on a suitable carrier which is adapted to be moved by movement of the foot pedal.

Abstract: An indicator circuit for indicating to the operator of an electrically propelled vehicle the remaining capacity of the vehicle battery. The state of charge information is indicated in digital form for facilitated readout. The circuit is arranged to prevent an increase in the indicated state of charge during use of the battery as a power source, i.e. in a motoring mode. The circuit is arranged to prevent a decrease in the indication of the state of charge during a recharging of the battery. The circuit utilizes a feedback signal from the digital counter portion thereof for comparison with a second signal produced in the control circuit to provide either a count-up signal to the digital counter or a count-down signal to the digital counter in providing the control of the operator indicator. The feedback signal may be converted to an analogue signal for comparison with the produced circuit signal in a comparator to provide the appropriate count-up or count-down signal.

Abstract: An on-board charger for an electric vehicle propulsion system which provides high charging capacity with minimum weight addition by sharing major elements of the electric vehicle power converter. In the preferred construction, the vehicle power converter has a magnetic element, an interphase transformer, connecting the output of the converter to the motor load. A primary winding is added to the interphase transformer for connection to a commercial AC power source. A phase controlled bridge also connected to the interphase transformer rectifies the AC power for charging the battery.

Abstract: A power converter having improved efficiency and useful, for example, in the propulsion system of an electric vehicle. The power converter includes a dual chopper having an output level variable over a rather wide range for controlling the speed of the vehicle from stop to cruising. A commutating inverter is transformer coupled to the chopper for commutating thyristors in the chopper. Efficiency is considerably enhanced by programming the amount of energy in the commutating inverter in accordance with the power being delivered by the chopper so as to minimize power losses and thereby increase the range of the vehicle.

Abstract: In a charger for the battery of an electric vehicle, a stable time of day clock is provided to initiate charging at a preselected time of day, and to control at least a portion of the charge cycle. The clock can be set in accordance with the schedule established for the vehicle so that charging will be accomplished automatically during the scheduled time of day when the vehicle is not in use. In the case of a fleet of such vehicles, at the termination of use, each driver simply parks the vehicle and connects an AC power line; charging for each vehicle will be initiated as determined by the clock associated therewith. An indicating system is provided to advise the driver that power has been properly connected and charging will commence at the appropriate time.

Abstract: A propulsion system for an electric vehicle in which a chopper is used to provide controlled DC power to a separately excited DC propulsion motor. In order to provide increased torque for comparatively short intervals to meet on-the-road requirements, the propulsion motor is provided with two sets of shunt field windings, and switch means are provided for connecting the windings in series or in parallel dependent upon the torque demands on the system. Normally the system is operated with the shunt field windings in series. To meet transient demands for increased torque, such as rapid acceleration from a stop light or improved gradability on hills, means are provided for detecting such increased torque demands and switching the field windings from series to parallel configuration thereby increasing the field flux and causing the motor to produce increased torque. The parallel connected field windings compensate for the demagnetizing effect of high armature currents without the need for a series field winding.

Abstract: A variable duty cycle power converter operable in a current controlled loop and having means for delivering increased load current at low duty cycles for efficient use of the switching elements in the converter. A current limit is established for maximum duty cycle which allows current flow through the power switching elements near but within the ratings of the devices. The maximum limit is programmed as a function of duty cycle to allow increased load current flow while maintaining the current through the power switching devices within ratings. As a result substantially increased current can be provided at low duty cycles without the need for using power switching devices of increased rating.

Abstract: A propulsion system for an electrical vehicle including a linear proportional controller operable in a plurality of modes for operating a d.c. drive motor via power derived from a propulsion battery. Low speed operation is achieved in an armature control mode wherein the controller is interposed between the propulsion battery and the motor armature while the motor field is coupled directly across the battery. High speeds are attained in a field control mode wherein the controller is interposed between the battery and motor field while the armature is coupled directly across the propulsion battery, thereby eliminating controller losses from the high current armature circuit. Switching between modes is achieved in a manner which minimizes stress on the switching elements. The controller is also adapted to operate in a charger mode wherein unregulated d.c. power is fed to the controller which functions to regulate the charge provided to the battery.

Abstract: A power converter for operation with a d.c. power supply to provide an output voltage having a level controlled in response to an external control signal. The converter uses a dual chopper configuraton with the out of phase outputs from the respective chopper halves being combined in an interphase transformer. To prevent the interphase transformer from saturating, the chopper control includes an oscillator, counter, D/A converter and phase delay comparator arrangement for maintaining substantially identical duty cycles in the respective legs while, of course, allowing the duty cycles to be varied in unison. The interphase transformer is wound in a configuration which presents a magnetic shunt between the halves of the transformer, said shunt serving to limit transients which might be coupled to the chopper load.

Abstract: A circuit for detecting and indicating the actual state of charge of a storage battery in response to signals sampled from various points in the circuit powered by the battery. Such circuit is adapted to calculate the open circuit voltage of the battery, it being realized that the open circuit voltage is directly proportional to the battery state of charge. A function generator is constructed to simulate the characteristic curve of the battery relating the internal resistance to the percent charge. Feedback is provided from the output of the indicating circuitry to the bias point of the function generator for causing the generator to produce a signal related to the actual internal resistance of the battery. The circuit is adapted to provide a reliable indication of the amount of usable energy remaining in the battery, irrespective of the conditions under which the battery was discharged.

Abstract: A charging circuit adapted to harvest excess energy from a resonating power circuit and use that energy for charging a battery. Energy is inductively transferred from the power circuit to the charging circuit allowing such circuits to remain electrically isolated. The charging circuit utilizes gate controlled thyristors for coupling the harvested energy to the battery and includes means for gating the thyristors at the proper time with respect to the resonant cycle in the power circuit.