Induction Motor Restart Control During Power Loss and Backspinning
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Solution Overview
Problem
Electric submersible pumps experience significant downtime and production losses due to power outages, as the pump cannot be restarted while backspinning, leading to fluid drainage and potential motor overvoltage issues during power restoration.
Innovation Solution
A method using a variable-speed drive system that measures DC bus voltage and magnetic flux to disable and re-enable power supply, allowing the motor to maintain operation and restart smoothly during short power glitches, employing sensors and controllers to manage the electric motor's rotational speed and flux feedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump motor is restarted immediately after power restoration, then continuous operation is improved, but motor overvoltage and drive tripping occur due to regeneration during backspinning
Solution Approach 1:
The system performs preliminary detection of motor rotational direction and speed before enabling restart. The controller detects whether the motor is backspinning and estimates its rotational speed, then configures the variable speed drive output signal accordingly to prevent overvoltage conditions before they occur.
Solution Approach 2:
The system dynamically adjusts the variable speed drive output signal based on real-time motor conditions. The controller continuously monitors magnetic flux feedback signals and DC bus voltage, adjusting the output signal configuration to match the motor's actual rotational state, enabling smooth transition from backspinning to forward operation.
2Loss of energy
If the pump is shut down during power outage, then energy consumption is reduced, but fluid drainage and production loss occur
Solution Approach 1:
The system uses magnetic flux feedback signals from the motor to continuously monitor rotational speed and direction during power outages. This feedback enables the controller to detect backspinning conditions and determine the optimal restart moment, allowing the pump to remain in a controlled state rather than fully shut down, thereby preventing fluid drainage while minimizing energy consumption.
Solution Approach 2:
The system uses the motor's own magnetic flux signals during coasting to provide speed and direction information, eliminating the need for additional sensors. The motor's residual magnetic flux serves the dual purpose of indicating its state and enabling the controller to make intelligent restart decisions.
3Loss of time
If the variable speed drive output is continuously monitored, then restart timing is optimized, but system complexity increases
Solution Approach 1:
The system uses the existing DC bus voltage as an intermediary indicator of power restoration. By monitoring this existing parameter along with magnetic flux feedback, the controller can determine restart timing without adding complex external sensors or measurement systems, thus minimizing system complexity while optimizing restart timing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables continuous operation and reduced downtime for electric submersible pumps by managing power supply and motor speed during power outages, preventing fluid drainage and motor overvoltage, thus minimizing production losses.
Implementation Method 1
measuring a magnetic flux signal from a stator of the electric motor to determine a rotational speed of the motor and characteristics of an output signal from the variable-speed drive
Implementation Method 2
an attempt to accelerate the motor while it is backspinning to its normal forward motion will cause regeneration, and likely trip the pump drive on DC bus overvoltage
Data Source
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AI summary
A method of operating an electric induction motor with a variable-speed drive includes determining a voltage level on a DC bus for the drive, and measuring a first magnitude of magnetic flux from a stator of the normally-operating electric motor, determining a normal flux level. The method includes disabling a first output to the drive when the DC bus voltage is less than a first threshold level. The method includes measuring a magnetic flux feedback signal having a phase and second magnitude, estimating a speed of the electric motor, and configuring a second output signal for the drive when the DC bus voltage is greater than a second threshold level. The second output signal matches a signal from the second magnitude and a phase of magnetic flux. The method includes enabling the drive output to restart the electric motor when the magnetic flux is greater than a third threshold value.