Motor Controller Speed Search for Power Failure Recovery
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Solution Overview
Problem
Motor controllers face challenges in synchronizing the rotational frequency of a motor with the output frequency of an inverter after a power failure, leading to issues like torque jerks, overcurrent, and overvoltage due to discrepancies between the two frequencies.
Innovation Solution
A motor controller system that includes an inverter and a controller, which supplies AC current to a stationary orthogonal coordinate system with a predetermined phase relationship, allowing the inverter to change the frequency of the AC current to match the motor's rotational frequency, enabling accurate detection and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inverter supplies power to the motor after recovery from instantaneous power failure, then the motor can resume operation, but wide discrepancy between motor rotational frequency and inverter output frequency causes torque jerks, overcurrent, and overvoltage
Solution Approach 1:
The motor controller performs speed search processing before the inverter supplies power to the motor after recovery from instantaneous power failure. This preliminary action detects the rotational frequency of the motor in free-run state, allowing the inverter output frequency to be matched to the motor's actual rotational frequency before power supply resumes, thereby preventing torque jerks, overcurrent, and overvoltage
Solution Approach 2:
The motor controller implements a feedback mechanism where the detected rotational frequency of the motor is used to adjust and match the inverter output frequency. By continuously monitoring the motor's rotational frequency and adjusting the inverter output accordingly, the system ensures synchronized operation and prevents harmful effects such as overcurrent and overvoltage
2Reliability
If the motor controller keeps the inverter from supplying power to the motor during instantaneous power failure, then the motor enters free-run state, but wide discrepancy between motor rotational frequency and inverter output frequency occurs after power recovery
Solution Approach 1:
The motor controller performs speed search processing as a preliminary action before resuming power supply to the motor. This detection process occurs while the motor is in free-run state, allowing the system to capture the motor's actual rotational frequency and use this information to synchronize the inverter output frequency, thereby resolving the frequency discrepancy issue
Solution Approach 2:
The motor controller changes the inverter output frequency parameter to match the detected motor rotational frequency. By adjusting the frequency parameter based on the speed search results, the system transitions from a state of frequency discrepancy to synchronized operation, preventing torque jerks and overcurrent when power supply resumes
Data Source
AI summary
A motor controller includes an inverter including circuitry which supplies power to a motor, and a controller including circuitry which controls the inverter such that the circuitry of the inverter supplies an AC current to a first axis of a stationary orthogonal coordinate system in the motor while changing a frequency of the AC current. The first axis has a predetermined phase relationship with a phase voltage of the motor.