Abstract: An improved downhole pumping system that employs a variable speed PWM inverter and a non-gap transformer to drive an induction motor over a range of different speeds, without saturating the transformer. The variable speed PWM inverter provides a rectangular PWM signal that may be varied according to inputs from a controller to adjust the speed of the motor. The PWM inverter is electrically connected to the transformer, and the transformer is electrically attached to the motor via cables, which may be lengthy in downhole applications. The motor may be started by ramping flux producing current to a first preset value at a low frequency, then ramping torque producing current to a second preset value. If a flux measurement indicates the motor has stalled, the second preset value is increased, and the routine is restarted. Otherwise, if no stall has occurred, the motor's speed is ramped to the desired value.

Abstract: An improved downhole pumping system that employs a variable speed PWM inverter and a non-gap transformer to drive an induction motor over a range of different speeds, without saturating the transformer. The variable speed PWM inverter provides a rectangular PWM signal that may be varied according to inputs from a controller to adjust the speed of the motor. The PWM inverter is electrically connected to the transformer, and the transformer is electrically attached to the motor via cables, which may be lengthy in downhole applications. The motor may be started by ramping flux producing current to a first preset value at a low frequency, then ramping torque producing current to a second preset value. If a flux measurement indicates the motor has stalled, the second preset value is increased, and the routine is restarted. Otherwise, if no stall has occurred, the motor's speed is ramped to the desired value.

Abstract: The stator terminals of an adjustable speed a-c induction motor are connected to a source of d-c electric power by means of an inverter, and a system is provided for blending both dynamic and regenerative electrical braking of the motor whenever it decelerates. The brake blending system comprises a plurality of braking resistors respectively coupled by a corresponding switch in parallel with the power source. The switches are controlled by a control circuit which responds to motor terminal voltage, motor angular velocity and the difference between the commanded and actual motor torques to determine the additional current which the motor could regenerate without exceeding commanded parameters. When the additional current corresponds to that current which can be absorbed by adding an additional stage of braking resistance, the control circuit actuates a switch to add a stage of dynamic brake resistance.

Abstract: Apparatus for electronically simulating the response of a direct current traction motor to predetermined operating states whereby there is provided a resultant signal representative of the torque that would be produced by an actual motor operating in the prescribed states. The apparatus calculates E per RPM for the simulated motor from measured values of available armature voltage and armature velocity. A function generator thereafter converts the E per RPM signal to a signal representative of the motor field current based upon known values for the simulated motor. The field current signal is converted to an armature current signal by a circuit which responds to the motor commanded state of field weakening to compute the instantaneous ratio of armature current to field current under the commanded conditions and thereafter multiplies the field current signal by that ratio to obtain a signal representative of armature current.

Abstract: A method and apparatus for rapidly detecting acceleration variations in a moving object by monitoring the instantaneous velocity of the object. A signal representative of instantaneous velocity is operated on to derive signals representative of average acceleration, instantaneous acceleration and predicted velocity. The average acceleration and instantaneous acceleration signals are compared to determine acceleration changes. In a preferred embodiment the invention is applied as a wheel slip/slide detector in a traction vehicle and a signal generated when the instantaneous acceleration deviates from the average acceleration by a predetermined magnitude is utilized as a wheel slip/slide signal to implement corrective action to the power control system of the vehicle. Upon generation of the wheel slip/slide signal, calculation of average acceleration is inhibited to prevent its influence by the sudden acceleration change.

Abstract: Alternating voltage for energizing an adjustable speed a-c motor is derived from unipolarity input voltage by means of electric power inverting apparatus comprising at least one pair of alternately conducting controllable electric valves. The conducting states of these valves are periodically switched by control means responsive to frequency and amplitude command signals, whereby the frequency and the amplitude of the fundamental component of the alternating voltage are varied as functions of the respective command signals. The control means includes means for implementing a triangle interception mode of pulse width modulation (PWM) of the alternating voltage so long as the amplitude command signal does not exceed a predetermined reference value (which is less than 1.

Abstract: A new induction motor control method and system utilizes one more electric power inverters each supplying a separate induction motor with alternating current excitation power. The respective inverters preferably comprise auto-sequential commutated controlled current inverters. Direct current is supplied to each inverter in the system from a common direct current power supply preferably comprising a phase controlled rectifier circuit with individual current smoothing inductors connected in the direct current link to each power inverter for isolation purposes. A common operator controlled power level control module is provided for controlling the magnitude of the output current supplied from the common phase controlled rectifier to all of the inverters in parallel. Respective motor flux sensing means are provided for each induction motor for deriving individual feedback control signals representative of the flux developed by the respective induction motors.

Abstract: A new and improved motor control method and system wherein the frequency of the rotating electro-magnetic flux produced in an alternating current machine, is sensed and compared to a desired value of machine flux frequency to derive an output error control signal. The output error control signal is then applied to control the frequency of the alternating current supplied to the machine in a direction and by an amount necessary to zero any difference in the sensed frequency and the desired frequency of machine flux. In preferred embodiments the actual value of the electromagnetic flux produced across the rotor-stator gap of the motor, is sensed and used as the controlling criterion in the motor control system. The magnitude of the alternating current supplied to the motor is separately controlled in accordance with some other predetermined motor operating characteristics such as motor torque, load current, etc.

Abstract: A torque regulating alternating current induction motor control system comprising a motor flux sensing coil arrangement mounted on the induction motor stator for sensing the actual flux produced across the rotor-stator air gap of the motor and deriving a motor flux voltage signal proportional to the actual motor flux. An integrating circuit integrates the voltage signal to obtain a feedback sensed actual motor flux signal representative of the actual air gap flux. An actual torque feedback circuit converts the actual air gap flux and stator current signal to an actual value of torque feedback control signal. A first feedback control loop is responsive to the actual torque feedback control signal and a command value of torque signal and controls the frequency of operation of a power converter supplying the induction motor.

Abstract: A flux sensing coil is installed in each phase of the motor stator, and the resulting induced voltages represent the rate of change of air gap flux in that phase. The output voltage signals are integrated, rectified and summed to obtain an average motor flux signal which is in turn applied to vary the voltage to the motor in such a manner as to maintain a substantially constant motor flux level. In this way control errors due to motor parameter changes are eliminated and the flux margin normally required in motor design is reduced to achieve a more efficient utilization of the motor.