Borehole Pump Motor Coil Pack for Axial Stator Insertion
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Solution Overview
Problem
Borehole pumps with wet rotor electric motors face challenges due to the limitations of submarine cables, including lower power density, higher axial length, and the inability to easily repair or recycle the stator, which affects performance and sustainability.
Innovation Solution
The design of an electric motor with a stator pack that allows for axial insertion of a coil pack with cast distributed windings, enabling high power density and ease of repair by producing the coil pack ex situ and inserting it into the stator, which can be prefabricated with uncoated winding wire to maximize copper cross-section filling and reduce axial length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If submarine cables with plastic insulation are used in the stator slots, then the motor is waterproof and can operate in flooded conditions, but the fill factor of copper in the slots is reduced due to the large radial thickness of the insulation
Solution Approach 1:
The motor is divided into two separate assemblies: a stator assembly with slots and a coil assembly with windings. The coil assembly is manufactured separately with unshielded conductors for maximum copper fill, then inserted as a complete unit into the stator assembly. This segmentation allows the copper-rich coil assembly to be produced independently without plastic insulation constraints, while the stator assembly provides the waterproof enclosure through its sealed structure.
Solution Approach 2:
A potting compound serves as an intermediary material that fills the cavities between the unshielded electrical conductors and the stator core. This potting compound provides the necessary insulation and waterproofing properties that would otherwise require thick plastic sheathing, allowing the use of unshielded conductors with maximum copper cross-section while maintaining flooded motor capability.
2Quantity of substance
If the stator is encapsulated with the coils potted directly in the stator core, then the power density is increased with larger copper cross-section, but the motor loses repairability since the electrical part cannot be separated from the mechanical part
Solution Approach 1:
The motor is divided into two separable assemblies: a stator assembly and a coil assembly. The coil assembly containing the potted coils can be removed and replaced independently from the stator assembly. This segmentation maintains the benefits of potted construction (high fill factor, waterproofing) while enabling repairability by allowing the coil assembly to be extracted and replaced without damaging the stator core.
3Manufacturing precision
If the winding head extends to the full diameter of the stator bore, then the coils can be properly positioned in the slots, but the coil assembly cannot be inserted axially into the stator
Solution Approach 1:
The winding head of the coil assembly is designed to extend only between an inner diameter and an outer diameter that is smaller than the diameter of the stator bore. This dimensional reduction in the radial direction enables axial insertion of the coil assembly into the stator. The coils are then positioned in the slots through axial movement and radial deformation, transitioning from a radial positioning problem to an axial insertion problem that can be solved by dimensional reduction.
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
This approach results in a cost-effective, high-power-density electric motor with reduced axial length and the ability to repair or replace the stator winding easily, enhancing performance and recyclability.
Implementation Method 1
The material used for potting is typically a casting resin that fills the cavities between the unshielded electrical conductors and between the electrical conductors and the stator core
Data Source
Figure 1~3c
Figure 1a~1c
Figure 4~5b
AI summary
The invention relates to an electric motor for a borehole pump with a stator assembly (1) comprising a stator bore (9) for receiving a rotor (13) and radially inwardly open slots (4, 4a), each separated from the other by a stator tooth (3). Electrical conductors (11) made of round wire from coils (6) of a coil assembly (5) are inserted into these slots, forming distributed windings and a winding head (7) at an axial end of the coil assembly (5), wherein the coils (6) are encapsulated. The winding head (7) extends only between an inner diameter (di) and an outer diameter (da), which is smaller than the diameter (Db) of the stator bore (9). The coil assembly (5) is axially inserted into the slots (4, 4a) of the stator assembly (1). This facilitates easy assembly and repair of the stator.The invention further relates to a method for manufacturing the electric motor and a tool (20, 20') for manufacturing the coil pack (5) from distributed windings for axial insertion into the stator pack (1) of the electric motor.