Motor Drive Pressure Compensation for Submersed Pumps
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Solution Overview
Problem
Submersed electric motors with integrated power supply and control units face challenges in maintaining optimal pressure conditions and minimizing dielectric cooling liquid leaks due to hydrostatic pressure variations, which can damage electronic components and compromise seal integrity.
Innovation Solution
A motor drive design incorporating a first bellows member to create a slight overpressure within the electric motor casing and an expansion compensation means within the power supply and control unit casing, using elastic materials and counterpressure valves to maintain independent pressure conditions and minimize leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional membrane is used to balance pressure inside the casing with outside pressure, then volume variations of dielectric cooling liquid are compensated, but the electronic components in the power supply and control unit are subjected to high hydrostatic pressure that can damage them
Solution Approach 1:
The patent divides the pressure compensation function into two separate systems: a first bellows member in the motor chamber that creates slight overpressure to reinforce the mechanical seal, and a second bellows member in the control unit chamber that maintains stable pressure to protect electronic components. This segmentation allows each system to optimize for its specific function without compromise.
Solution Approach 2:
Different pressure conditions are applied to different parts of the system: the motor chamber experiences slight overpressure (higher than hydrostatic) to enhance seal performance, while the control unit chamber maintains stable pressure (equal to hydrostatic) to protect electronics. Each region has customized pressure characteristics suited to its functional requirements.
2Reliability
If pressure inside the casing is made equal to outside pressure, then volume variations of dielectric cooling liquid are accommodated, but the thrust of springs in the rotary mechanical seal becomes inadequate when liquid becomes more fluid due to heating
Solution Approach 1:
The first bellows member is pre-configured to generate a slight overpressure within the motor chamber during normal operation. This preliminary pressure buildup ensures that the springs in the rotary mechanical seal always have sufficient thrust to maintain tightness, even when the dielectric cooling liquid becomes more fluid due to motor heating.
3Volume of moving object
If power supply and control unit are placed close to the motor to compact dimensions, then device size is reduced, but electronic components are exposed to severe risk of damage from hydrostatic pressure
Solution Approach 1:
The patent segments the pressure management into two independent systems: the first bellows member serves the motor chamber with overpressure for seal reinforcement, while the second bellows member serves the control unit chamber with stable pressure for electronics protection. This allows compact integration of both units while maintaining their distinct pressure requirements.
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 solution effectively balances dielectric cooling liquid volume variations, reinforces the rotary mechanical seal, and maintains stable pressure within the power supply and control unit enclosure, minimizing leaks and allowing operation at higher temperatures while maintaining independent physical conditions between the two compartments.
Implementation Method 1
a first bellows member (50), which is elastically deformable and accommodated in a first seat (13) that is formed in the bottom (3)
Implementation Method 2
an expansion compensation means for absorbing the volume variations of the dielectric cooling liquid that fills the second hermetic chamber (81)
Implementation Method 3
counterpressure valves to maintain independent pressure conditions
Data Source
Figure 1
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Figure 3
AI summary
A motor drive, particularly for submersed electric pumps, has a jacket closed hermetically by a bottom and a head in order to form a first hermetic chamber, which contains an electric motor that is immersed in a bath of dielectric cooling liquid; the jacket is associated with an enclosure in order to form a second hermetic chamber, which contains a power supply and control unit connected to the electric motor. The motor drive includes a compensation means that balances the variations in volume of the dielectric cooling liquid and generates an overpressure within the first hermetic chamber; the first hermetic chamber is substantially independent of the second hermetic chamber.