ESP Rotor Position Sensing Through Three-Phase Power Cable

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Solution Overview

Problem

Existing ESP assemblies require a four-wire cable for rotor position feedback, which is not suitable for space-constrained applications, and synchronous reluctance motors need rotor position information but are limited by the need for additional cables.

Innovation Solution

A method and system for transmitting electricity through a power cable to operate a permanent magnet motor in an ESP assembly, using a current transformer to monitor the angular position of the drive shaft and adjust electricity transmission based on sensed magnetic fields, allowing for rotor position feedback without additional cables.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a four-wire cable is used for rotor position feedback in synchronous reluctance motors, then rotor position feedback is achieved, but cable space requirements increase

Engineering Contradiction:

Improverotor position feedbackVSAvoidcable space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines the rotor position feedback signal transmission with the existing three-phase power cable by using one of the power lines as a communication channel. Current transformers are used to extract position information from the power cable currents, eliminating the need for a separate fourth wire for position feedback.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The power cable is made multi-functional by using it both for power transmission and for rotor position feedback. The system extracts position information from the current flowing through the power cable, allowing the same cable to serve dual purposes and reducing overall cable requirements.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If rotor position sensing is implemented in ESP assemblies, then operational reliability beyond three kilometers is improved, but device complexity increases

Engineering Contradiction:

Improveoperational reliabilityVSAvoidsensing system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces current transformers as intermediary devices that enable position sensing without direct complex sensing hardware in the motor. The current transformers convert position-related current information into usable signals, simplifying the overall sensing system architecture while maintaining reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system implements feedback by continuously monitoring current through the power cable and using this information to determine rotor position. This feedback mechanism enables reliable operation beyond three kilometers by providing the necessary position information for proper motor control.

Inventive Principle:

Principle #23Feedback

3Device complexity

If three-phase power cables are used without rotor position capability, then cable simplicity is maintained, but motor control precision deteriorates

Engineering Contradiction:

Improvecable simplicityVSAvoidmotor control precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent replaces complex mechanical or separate electrical position sensing systems with an electrical measurement approach using existing power cable currents. By measuring current characteristics through the power cable, the system achieves precise rotor position information without adding mechanical complexity or requiring additional position-sensing cables.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 efficient operation of ESP assemblies beyond three kilometers by providing real-time rotor position feedback, enhancing operational reliability and reducing cable requirements.

Implementation Method 1

monitoring an angular position of a drive shaft of the ESP assembly that is in the wellbore, using a current transformer to communicate information about the angular position to the power cable

Methodology Applied

Scientific EffectMagnetic field sensing: Magnetic Field

Implementation Method 2

the angular position is monitored by sensing the presence of an asymmetric magnetic field projecting radially from an end of the drive shaft

Methodology Applied

Scientific EffectAsymmetric magnetic field: Magnetic Field

Implementation Method 3

transmitting electricity from a variable speed drive and through a power cable to operate a permanent magnet motor of the ESP assembly

Methodology Applied

Scientific EffectElectromagnetic conversion: Electromagnetic Induction

Data Source

PatentUS12480391B2Controlling downhole electrical submersible pump based on sensing rotor position

Publication Date: 2025.11.25 RMSPUMPTOOLS

AI summary

An ESP assembly includes a motor having a stator, a rotor, a drive shaft, and an asymmetric magnetic ring mounted to an end of the drive shaft. Electricity for driving the motor is provided by a power source on surface and delivered to the motor through a power cable inserted into the wellbore. Power cable leads insert into a star connection mounted around an end of the shaft having the ring and that houses a downhole sensor. During operation of the ESP assembly, the sensor tracks the rotor position by monitoring ring rotation. Information about the rotor position is transmitted uphole along the power cable. A controller on surface receives and processes the position information, and delivers control commands to the motor that are transmitted down the power cable. The power cable is connected to the controller and to the sensor by current transformers.