Multi-Phase PM Motor Current Balancing via Voltage Adjustment
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Solution Overview
Problem
Existing multi-phase permanent magnet rotor motors face inefficiencies due to imbalances in torque between stator coils caused by variations in coil parameters such as resistance and inductance, resulting from manufacturing imperfections or wear, leading to reduced motor efficiency.
Innovation Solution
A method involving pulse modulated control signals is applied to adjust multi-phase stationary reference frame voltages for phase coils, ensuring balanced torque by measuring and adjusting current values until they equal or fall within a predetermined range of a selected phase coil current, using a modified field-oriented control system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standard motor control is used assuming identical phase coils, then device complexity is reduced, but manufacturing precision deteriorates due to coil parameter variations
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the control voltages for each phase based on measured current deviations. The controller modifies the voltage parameters in real-time to compensate for manufacturing variations in coil resistance and inductance, thereby achieving balanced torque without requiring perfectly identical coils.
Solution Approach 2:
The patent implements feedback control by measuring the actual current in each phase coil and using this information to adjust the control voltages. The controller continuously monitors phase currents and modifies the PWM duty cycles to maintain equal current levels across all phases, compensating for manufacturing tolerances.
2Ease of manufacture
If coil parameter variations are not compensated, then ease of manufacture is improved, but motor efficiency deteriorates due to torque imbalance
Solution Approach 1:
The system changes control parameters (voltage amplitudes and PWM duty cycles) for each phase to compensate for manufacturing variations. By adjusting these parameters dynamically, the motor maintains balanced torque and high efficiency even when coil parameters vary within acceptable manufacturing tolerances.
Solution Approach 2:
The feedback mechanism measures actual phase currents and uses this information to adjust control voltages, ensuring that torque imbalance caused by manufacturing variations does not degrade motor efficiency. The continuous adjustment maintains optimal operating conditions despite coil parameter variations.
3Loss of energy
If phase coil currents are balanced through voltage adjustment, then motor efficiency is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The patent uses feedback control where the controller measures phase currents and automatically adjusts control voltages to maintain balanced operation. This feedback mechanism improves motor efficiency by compensating for coil variations while keeping the control system complexity manageable through automated closed-loop control.
Solution Approach 2:
The control system performs self-adjustment by automatically detecting current imbalances and correcting them through voltage modulation. The system serves itself by continuously monitoring and correcting its own operation, improving efficiency without requiring external intervention or overly complex control architecture.
4Ease of manufacture
If manufacturing variations in coil parameters are accepted, then ease of manufacture is maintained, but reliability deteriorates due to torque imbalance and potential overheating
Solution Approach 1:
The feedback control system continuously monitors phase currents and adjusts control voltages to prevent torque imbalance and overheating. This maintains reliability by ensuring balanced operation even when manufacturing variations exist, without requiring overly stringent production specifications.
Solution Approach 2:
The system dynamically changes control parameters to compensate for manufacturing variations, preventing reliability issues such as torque ripple and thermal stress. By adjusting voltages in real-time, the motor maintains reliable operation despite coil parameter variations within manufacturing tolerances.
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
This approach reduces torque imbalances, enhancing motor efficiency and maintaining consistent operation by adjusting motor control voltages and currents, thereby improving overall performance.
Implementation Method 1
outputting pulse modulated control signals to the respective phase coils to bring the motor to a constant mode of operation
Implementation Method 2
A permanent magnet motor uses permanent magnets in the rotor to provide a constant magnetic flux which typically has a sinusoidal back-electromotive force (emf) signal
Implementation Method 3
If a permanent magnet or electromagnet is present in this rotating magnetic field, the magnet is magnetically locked with the rotating magnetic field and consequently rotates at the same speed as the rotating field
Data Source
AI summary
A method of driving a multi-phase permanent magnet rotor motor having a plurality of phase coils. The method comprises outputting pulse modulated control signals to the respective phase coils to bring the motor to a constant mode of operation. Once the motor is in its constant mode of operation, the method includes measuring phase coil currents and, for a selected phase coil, adjusting values of multi-phase stationary reference frame voltages for only remaining phase coils by one or more predetermined increments until the phase coil currents of the remaining phase coils equals the phase coil current of the selected phase coil or until the phase coil currents of the remaining phase coils fall with a predetermined range with respect to the phase coil current of the selected phase coil.