Dual Motor Drive Phase Shift for Torsional Vibration Damping
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Solution Overview
Problem
Existing systems with mechanically coupled electric motors used for gas liquefaction, such as natural gas, face issues with excitation of natural vibrations, which can lead to damage or destruction if not damped or prevented.
Innovation Solution
The system employs intermediate current circuit converters with a phase shift between drives to dampen or eliminate natural oscillations, optimizing network feedback and preventing unwanted frequency coupling into the supply network, thereby eliminating the need for additional damping components or controls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two electric motors are mechanically coupled via a common shaft to drive a compressor system, then the system can achieve high power output (10 MW or more), but natural oscillations are excited in the strand which can damage or destroy the system
Solution Approach 1:
The patent applies asymmetry by introducing a phase shift angle between the two electric motors that is different from 0° or 180°. This asymmetric phase relationship causes the oscillating torques generated by each motor to cancel each other out, eliminating the excitation of natural oscillations in the strand while maintaining high power output capability
Solution Approach 2:
The patent changes the operational parameters of the motors by introducing a specific phase shift angle between them. This parameter change modifies the torque characteristics and frequency content of the oscillating torques, allowing the system to operate at high power while avoiding resonance conditions that would excite dangerous vibrations in the strand
2Reliability
If additional components or controls are added to prevent or control excitation of natural vibration, then system safety is improved, but manufacturing cost increases
Solution Approach 1:
The patent converts the potentially harmful oscillating torques generated by the motors into a beneficial effect by carefully controlling their phase relationship. The oscillating torques that would normally excite dangerous vibrations are instead configured to cancel each other out, eliminating the need for additional damping components or control systems while maintaining system safety
Solution Approach 2:
The system achieves self-protection against natural oscillations through the inherent phase shift between the two motors. The motors themselves generate counteracting oscillating torques that automatically dampen vibrations without requiring external damping devices, active control systems, or additional safety components, thereby reducing manufacturing costs while ensuring system safety
Data Source
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AI summary
The invention relates to a system with a first electric motor (12) and a second electric motor (14) which are mechanically coupled to each other via a common line section (17) of the system. The line section (17) exhibits a natural torsional vibration in response to a natural frequency. A first oscillating torque and a second oscillating torque act on the line section (17) by means of the first electric motor (12) and the second electric motor (14), respectively. According to the invention, the second electric motor (14) is arranged relative to the first electric motor (12) such that the influence of the second oscillating torque on the line section (17) leads to a damping of the excitation of the natural vibration due to the first oscillating torque.