PMSM Reverse Start Control Using Load Energy Thresholds
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Solution Overview
Problem
Conventional methods for starting a permanent magnet synchronous motor (PMSM) in reverse direction fail to consider both kinetic and potential energy, leading to starting failures when load changes, especially due to external wind resistance or load variations.
Innovation Solution
A method and device that estimate load torque and potential energy to control torque for decelerating the PMSM to a predetermined speed, then start it in a forward direction only when the total energy is below a threshold, considering both kinetic and potential energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional braking circuit method is used to reduce rotational speed to 0 before starting, then the PMSM can start in a stationary state, but the starting success rate fails when load changes due to potential energy not being considered
Solution Approach 1:
The patent changes the control parameter from only rotational speed to a comprehensive energy parameter that includes both kinetic energy (from rotational speed) and potential energy (from load position/weight). This allows the control system to accurately determine when the PMSM has truly stopped and is ready for reverse starting, regardless of load variations. The energy threshold comparison provides a more reliable stopping criterion that adapts to different load conditions.
2Device complexity
If only rotational speed is considered for controlling the PMSM during reversal, then the control is simple, but the PMSM may fail to start due to potential energy from different loads and inertia
Solution Approach 1:
The patent applies preliminary braking action based on energy estimation before the reverse starting attempt. By first estimating the total energy (kinetic + potential) and applying braking torque to reduce this energy below a threshold, the system ensures the PMSM is truly stationary and ready for reverse starting. This preliminary energy-based preparation action prevents starting failures that would occur with simple speed-based control.
Data Source
AI summary
A method for enabling a permanent magnet synchronous motor (PMSM) to start in a reverse direction may include: estimating a load torque according to a torque and an actual rotational speed of the PMSM, to generate an estimated load torque; controlling the torque according to the estimated load torque to decelerate the PMSM, until the actual rotational speed of the PMSM is reduced to a predetermined target rotational speed; in response to the actual rotational speed of the PMSM being reduced to the predetermined target rotational speed, determining whether an energy of the PMSM is not greater than a threshold value, wherein the energy of the PMSM comprises a potential energy; and in response to the energy of the PMSM not being greater than the threshold value, starting to control the torque for making the PMSM rotate in a forward direction.