Apparatus and method for controlling permanent magnet synchronous motor, and program
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Solution Overview
Problem
Permanent-magnet type synchronous motors used in vehicle air conditioners face challenges in smooth start-up due to unknown rotor position at startup, leading to increased start-up failures and power consumption, especially in hybrid and electric vehicles where power source efficiency is critical.
Innovation Solution
A control device for permanent-magnet type synchronous motors that sets a synchronous operation current based on the inverter's temperature, monitors and updates the current during rotation stabilization, and determines liquefaction of refrigerant using output voltage or current, allowing for efficient and reliable motor operation without the need for position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If constant current is applied without knowing compressor condition, then motor can be started, but start-up failure rate increases
Solution Approach 1:
The control device performs preliminary actions by detecting rotor position before start-up, determining compressor operating state, and setting appropriate starting current and frequency based on these preliminary detections, thereby improving start-up reliability without causing failures
Solution Approach 2:
The control device uses feedback by continuously monitoring output voltage and current during rotation stabilizing period, detecting rotor position, and adjusting starting parameters based on feedback about compressor state and motor performance, which reduces start-up failure rate
2Reliability
If high current is applied to ensure motor starts, then start-up success rate improves, but inverter damage risk increases
Solution Approach 1:
The control device applies dynamic current limiting that adjusts the current limiting value based on inverter temperature conditions. When inverter temperature is high, the current limiting value is reduced to prevent damage; when temperature is low, higher current can be applied to ensure reliable start-up, thus dynamically balancing reliability and safety
Solution Approach 2:
The control device changes operating parameters by setting different current and frequency combinations based on detected rotor position and compressor state. This parameter optimization ensures motor starts reliably while keeping current within safe limits for the inverter, preventing damage
3Measurement precision
If position sensor is installed to improve control accuracy, then rotor position can be detected, but device complexity increases
Solution Approach 1:
The control device performs self-service by using the motor's own back-EMF and current characteristics to detect rotor position without external sensors. The system serves itself by extracting position information from operational parameters, eliminating the need for additional position sensors and reducing device complexity
Solution Approach 2:
The control device replaces mechanical sensor systems with electrical measurement methods. Instead of using physical position sensors that require lubricant-proof sealing, the system uses electrical signals (back-EMF, current) to detect rotor position, substituting a mechanical sensing system with an electrical field-based detection method
4Reliability
If multiple monitoring functions are added to prevent start-up failure, then reliability improves, but device complexity increases
Solution Approach 1:
The control device achieves multi-functionality by using a single control system that performs multiple functions: rotor position detection, compressor state determination, current limiting value setting, and starting parameter optimization. This universal approach improves reliability without requiring separate dedicated systems for each function, thereby limiting complexity increase
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
The solution enhances the start-up success rate of the motor, reduces power consumption, and prevents inverter damage by setting currents close to the current limiting value, while simplifying the device configuration by eliminating the need for sensor information.
Implementation Method 1
an inverter that supplies three-phase power to the permanent-magnet type synchronous motor
Implementation Method 2
permanent-magnet type synchronous motor used as a driving source of a compressor
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
There is provided a control device of a permanent-magnet type synchronous motor that sets a synchronous operation current at start-up in response to a current limiting value determined from the temperature of an inverter that supplies three-phase power to the permanent-magnet type synchronous motor, that monitors an output voltage or an output current of the inverter during a rotation stabilizing period after start-up, and that updates the synchronous operation current using this output voltage or output current.