Audible Noise Reduction in Single Current Shunt Motor Drives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The single current shunt feedback topology in PWM inverter drives generates significant audible noise, particularly at low motor speeds due to minimum pulse constraints required for reliable current sampling, leading to increased harmonic noise and unacceptable noise performance.
Innovation Solution
The method involves removing current samples within a PWM cycle when motor speed drops below a certain threshold, reducing the need for minimum pulse constraints and thereby reducing audible noise by averaging and compensating for voltage errors in the motor drive system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If minimum pulse constraint is imposed for reliable current sampling, then current feedback reliability is improved, but audible noise increases
Solution Approach 1:
The patent applies dynamics by adaptively adjusting the feedback sampling rate and controller bandwidth based on motor speed conditions. At low speeds where audible noise is prominent, the sampling rate is reduced to minimize minimum pulse constraints, while at higher speeds nominal sampling rates are restored to maintain reliability. This dynamic adaptation resolves the contradiction between reliability and noise reduction.
Solution Approach 2:
The patent changes operational parameters (feedback sampling rate and controller bandwidth) based on motor speed thresholds. When motor speed drops below a certain threshold, the sampling rate is reduced from nominal to a lower value, which reduces the frequency of minimum pulse constraints and thereby reduces audible noise while maintaining sufficient current feedback reliability for the application.
2Measurement precision
If feedback sampling rate is increased to improve current measurement precision, then measurement precision is improved, but audible noise increases
Solution Approach 1:
The feedback sampling rate is dynamically adjusted based on motor speed. At low speeds where audible noise is most prominent, the sampling rate is reduced to minimize the generation of noise through frequent minimum pulse constraints. At higher speeds, the nominal sampling rate is maintained to ensure sufficient measurement precision for accurate current feedback control.
3Object-generated harmful factors
If minimum pulse constraint is reduced to decrease audible noise, then audible noise is reduced, but current sampling reliability deteriorates
Solution Approach 1:
The controller adaptively changes the feedback sampling rate parameter based on motor speed conditions. When motor speed is above a threshold, nominal sampling rate maintains reliable current sampling. When motor speed drops below the threshold, the sampling rate is reduced to minimize minimum pulse constraints and thereby reduce audible noise, accepting a trade-off in sampling frequency that is appropriate for low-speed operation.
Data Source
AI summary
A method for reducing audible motor noise in a motor drive, wherein the motor drive includes a motor controller driving a PWM space vector modulator providing gating pulses to an inverter providing phase currents to the phase windings of the motor, and wherein phase currents of the motor are determined by taking samples of the DC link current in a DC link powering the inverter. The method comprises determining the speed of the motor and comparing the speed to a preset threshold, the preset threshold defining a speed at which audible noise is generated by the motor due to a minimum pulse constraint being imposed on the motor phase currents in order to reliably sample the DC link current to measure the phase current. If the speed is below the threshold, the DC link current in the DC link is sampled using a reduced number of current samples for a PWM cycle of the PWM space vector modulator to reduce audible motor noise.