Bearingless Motor Harmonic Control for Stable Shaft Support
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Solution Overview
Problem
Existing bearingless motors experience fluctuations in shaft support force due to spatial harmonics caused by the magnetic circuit's characteristics, leading to unintended vibrations in the rotary shaft.
Innovation Solution
The system controls the inverters to output a voltage or current with harmonics superimposed, where the harmonics are multiples of the rotational frequency by natural numbers, to stabilize the shaft support force and reduce radial vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bearingless motor control is used, then the motor can generate shaft support force and rotational torque, but spatial harmonics cause fluctuations in shaft support force leading to vibrations
Solution Approach 1:
The invention converts the harmful spatial harmonics into beneficial effects by superimposing correction harmonics on the inverter output. The control unit calculates correction amounts based on detected shaft support force fluctuations and adds harmonics at multiples of the fundamental frequency to cancel out the spatial harmonic effects, thereby reducing radial vibrations and stabilizing shaft support.
Solution Approach 2:
The invention implements a feedback control mechanism where the control unit continuously detects shaft support force fluctuations, calculates the required correction amounts, and adjusts the inverter output accordingly. The control unit superimposes correction voltages or currents based on the detected fluctuations and previously calculated correction amounts, creating a closed-loop system that actively compensates for spatial harmonic effects.
2Object-affected harmful factors
If harmonic correction is applied to reduce shaft support force fluctuations, then vibration is reduced, but control system complexity increases
Solution Approach 1:
The invention applies preliminary action by pre-calculating correction amounts based on the relationship between shaft support force fluctuations and harmonic components. The control unit stores these correction amounts and applies them proactively to the inverter output, preventing vibration issues before they manifest rather than reacting after problems occur.
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 allows for stable, smooth rotation of the rotary shaft by reducing the influence of spatial harmonics, ensuring consistent shaft support force independent of the electrical angle.
Implementation Method 1
A bearingless motor includes a rotor provided on the rotary shaft, and a stator provided radially outside the rotor and including a shaft support winding and a motor winding. The first inverter supplies electric power to the shaft support winding to generate a shaft support force for supporting the rotary shaft in a non-contact manner.
Implementation Method 2
The second inverter supplies electric power to the motor winding to generate a rotational torque in the rotary shaft.
Data Source
AI summary
A bearingless motor system includes a rotary shaft, a bearingless motor, first and second inverters, and a control unit. The motor includes a rotor, and a stator including a shaft support winding and a motor winding. The first inverter supplies electric power to the shaft support winding to generate a shaft support force to support the rotary shaft in a non-contact manner. The second inverter supplies electric power to the motor winding to generate a rotational torque in the rotary shaft. The control unit controls the first and second inverters. The control unit commands at least one of the first and second inverters to output a voltage or a current on which a harmonic is superimposed in order to reduce a fluctuation in the shaft support force. The harmonic is obtained by multiplication of a rotational frequency of the motor by a natural number of two or more.