Screw Pump Backspin Control via Regenerative Braking
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Solution Overview
Problem
Screw pumps experience backspin and productivity loss due to electrical power interruptions, which can cause equipment damage and safety hazards when stored energy is released uncontrolled.
Innovation Solution
A control system that converts stored potential energy from backspin into regenerative electrical energy to maintain motor drive operation, using a braking unit and resistor to control backspin and minimize equipment damage, ensuring immediate restart and enhanced safety and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the screw pump is shut down by stopping the motor drive, then the pump operation is decelerated and stopped, but the stored energy is released through backspin at very high speeds causing equipment damage
Solution Approach 1:
The patent converts the harmful backspin energy into useful regenerative electrical energy. When the motor drive is shut down, the pump rod's backspin drives the motor as a generator, producing electrical energy that is fed back to the DC bus. This eliminates the harmful high-speed backspin while capturing the energy for potential reuse, directly resolving the contradiction between equipment safety and productivity.
Solution Approach 2:
The control system acts as an intermediary between the mechanical backspin motion and the electrical system. It detects backspin conditions and controls the motor drive to enable regenerative braking, mediating the energy conversion process and preventing direct mechanical damage while maintaining system control throughout the shutdown process.
2Reliability
If electrical power is lost, then the screw pump loses control ability, but the stored energy causes prolonged backspin lasting several hours
Solution Approach 1:
The patent implements preliminary control actions by detecting power loss conditions and immediately activating the regenerative braking mechanism. The control system prepares and executes the energy conversion process before uncontrolled backspin can occur, maintaining control capability during power loss events and significantly reducing backspin duration.
Solution Approach 2:
During power loss, the stored energy that would cause prolonged uncontrolled backspin is converted into regenerative electrical energy. This eliminates the harmful effect of extended backspin duration while potentially storing energy for system restart, directly addressing both control capability and time loss issues.
3Loss of energy
If the DC bus voltage is allowed to rise during regenerative braking, then the regenerative energy can be stored, but excessive voltage damages the motor drive
Solution Approach 1:
The control system continuously monitors DC bus voltage during regenerative braking and provides feedback control. When voltage approaches dangerous levels, the system adjusts the braking torque or activates clamping circuits, creating a closed-loop control that maximizes energy recovery while protecting the motor drive from voltage damage.
Solution Approach 2:
The patent implements protective measures in advance by designing the motor drive with voltage clamping circuits and capacitive energy storage elements. These components are prepared beforehand to absorb or divert excess regenerative energy, preventing voltage damage before it occurs while still utilizing the energy effectively.
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
The control system effectively prevents equipment damage and ensures immediate restart of screw pumps by converting backspin energy, reducing downtime and enhancing safety and productivity.
Implementation Method 1
the regenerative energy, which is converted from the stored potential energy released by the backspin action of the pump rod
Implementation Method 2
using a braking unit and resistor to control backspin and minimize equipment damage
Implementation Method 3
using a braking unit and resistor to control backspin
Data Source
AI summary
A control method is used with a control system to control a screw pump. The control system includes an electric motor and a motor drive. The control method includes following steps. Firstly, a DC bus voltage is monitored. If the DC bus voltage is smaller than a first threshold value, a potential energy stored in the pump screw and released by a backspin action is converted into a regenerative electrical energy so as to maintain a normal operation of the motor drive. Then, the motor drive drives the electric motor to control the backspin action of the screw pump according to a backspin torque limit strategy. If the electrical power from the power source is not restored and the level of a reverse regenerative torque is smaller than a preset torque value, the backspin action of the screw pump is stopped freely.