Electric Machine Commutation for Low-Speed Rotor Position Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electrical machines, such as turbochargers, face challenges in accurately determining the rotor position at low speeds, leading to interference signals and distorted retroactive generator voltages due to sine commutation, which affects torque performance.
Innovation Solution
Switching to block commutation in a second speed range below the first speed range, where one phase is de-energized to determine rotor position using the retroactive generator voltage, and optionally using an additional sensor winding to simplify voltage detection, thereby avoiding interference and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sinusoidal commutation is used at low speeds, then smooth torque generation is achieved, but interference signals and distorted generator voltages occur due to branch locking times and high phase currents
Solution Approach 1:
The patent applies dynamics by switching between two commutation modes (sinusoidal and block) based on the operating speed range. At low speeds where interference occurs, block commutation is used; at higher speeds where sinusoidal commutation is suitable, it is applied. This dynamic adaptation resolves the contradiction by selecting the appropriate commutation method for each speed regime.
Solution Approach 2:
The patent changes the commutation parameter from sinusoidal to block commutation in the low-speed range. This parameter change eliminates the branch locking times that cause interference voltages during sinusoidal commutation at low speeds, while maintaining reliable rotor position determination through the characteristics of block commutation.
2Object-generated harmful factors
If block commutation is used at low speeds, then interference voltages are reduced, but torque smoothness may be affected
Solution Approach 1:
The system dynamically switches commutation modes based on speed. Block commutation is applied only in the low-speed range where it effectively reduces interference voltages, while sinusoidal commutation is used at higher speeds where it provides smooth torque. This dynamic approach balances the trade-off between interference reduction and torque smoothness.
Solution Approach 2:
Different commutation qualities are applied to different speed ranges. Block commutation with its specific characteristics is applied locally to the low-speed range where interference is the dominant issue, while sinusoidal commutation is applied to the higher speed range where smooth torque is more critical. This local differentiation resolves the contradiction.
3Measurement precision
If one phase is de-energized for rotor position detection, then position accuracy improves, but power output may be reduced
Solution Approach 1:
The system dynamically adjusts the commutation mode based on operating conditions. During low-speed operation where position detection is critical, block commutation with one phase de-energized is used to improve position accuracy. At higher speeds where power output is more important, sinusoidal commutation energizes all phases to maximize torque while using alternative position detection methods.
Solution Approach 2:
The de-energized phase for position detection is applied periodically or selectively during specific operating conditions (low speed range) rather than continuously. This periodic application minimizes the impact on power output while maintaining position detection accuracy when most needed.
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
Ensures precise rotor position determination and increased overall performance by reducing interference voltages and current plateaus, allowing for reliable operation from standstill to maximum speed.
Implementation Method 1
the drive winding is energized by block commutation in a second speed range, which lies below the first speed range... to generate a torque
Implementation Method 2
the angular position of the rotor is determined depending on phase currents induced into the drive winding by the rotor... the so-called back EMF
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to a method for operating an electric machine (5), in particular a turbocharger (1). The electric machine (5) has a multi-phase drive winding which is energized in order to generate a torque in at least one first rotational speed range by means of a sinusoidal commutation depending on the bar position of a rotor (7) of the electric machine (5). The angular position of the rotor (7) is determined on the basis of phase currents induced in the drive winding by the rotor. The drive winding is energized in a second rotational speed range which lies below the first rotational speed range by a block commutation.