BLDC Motor Drive Phase Correction for Reactive Power Loss
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Solution Overview
Problem
Existing DC motor drive systems face inefficiencies due to phase-shifts between phase voltages and EMF voltages, leading to unwanted reactive power generation and increased losses, especially during continuous drive, acceleration, and deceleration, which are not accurately addressed by existing methods like Field Oriented Control (FOC).
Innovation Solution
A method and circuitry for a BLDC motor drive system that includes a controller to sample the rotor's instantaneous angle, measure input power, and calculate phase differences to adjust the phase and level of input voltages applied to separate coils using a controlled inverter and up/down DC-DC converter, optimizing power transfer and phase correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Field Oriented Control (FOC) is used to correct phase-shift between phase voltages and EMF voltages, then motor efficiency is improved, but computing power requirements and system complexity increase
Solution Approach 1:
The patent changes the control parameter from complex real-time phase angle calculation to simple input power measurement. By measuring input power and using a pre-stored lookup table to determine phase correction values, the system avoids complex computing while achieving accurate phase correction and improved motor efficiency.
Solution Approach 2:
The patent uses a lookup table that stores pre-calculated phase correction values based on input power levels. This copying approach replaces complex real-time calculations with simple table lookups, significantly reducing computing power requirements while maintaining accuracy.
2Speed
If PWM is used to control motor speed, then speed control flexibility is improved, but switching losses increase during continuous drive and deceleration
Solution Approach 1:
The patent uses periodic six-step commutation instead of continuous PWM switching. By applying voltage in discrete six-step intervals synchronized with rotor position, the system achieves speed control while minimizing switching losses during continuous drive and regenerative braking operations.
3Device complexity
If phase correction is not applied, then system simplicity is maintained, but reactive power generation increases and reduces motor efficiency
Solution Approach 1:
The patent implements feedback by measuring input power and using this measurement to select appropriate phase correction values from a lookup table. This closed-loop approach ensures reactive power is minimized while maintaining system simplicity through straightforward measurement and table-based control.
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 provides efficient bidirectional power transfer and accurate phase correction, reducing computing power requirements and enhancing motor efficiency by optimizing the match between input voltages and currents, thereby minimizing power losses and improving motor performance.
Implementation Method 1
When a coil is activated, the generated magnetic field attracts/detracts one of the poles of the rotor magnets in order to start and maintain rotation
Implementation Method 2
the generated magnetic field attracts/detracts one of the poles of the rotor magnets
Implementation Method 3
the electromotive force (EMF) generated when the inductor passes (via rotation) a permanent magnet
Data Source
AI summary
A drive system for a BLDC motor having poles implemented by separate coils that are activated in corresponding phases, which comprises a controller for controlling the level and phase of input voltages supplied to the separate coils; a controlled inverter with outputs, for applying phase-separated input voltages to each of the separate coils at desired timing for each input voltage, determined by the controller; a power source for feeding power to the controlled inverter; an up/down DC-DC converter for converting the feeding power to the input voltages according to a command signal provided by the controller. The controller is adapted to sample the instantaneous angle of the rotor of the BLDC motor; sample the input voltage input voltage and the current of each phase to obtain the input power P; and for each input voltage, calculate the phase difference value that corresponds to the input power and feeds the phase difference value to the up/down DC-DC converter, thereby causing the up/down DC-DC converter to apply each input voltage to its corresponding coil at a specific timing for obtaining an optimal match between each input voltage and the current that is being built up in the corresponding coil.