Motor Control Device Reducing Losses via Dynamic V/F Ratio
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Solution Overview
Problem
Conventional motor control systems using V/F fixing control experience excessive motor loss and inefficiency in low-speed or light-load regions due to complex arithmetic processing and inadequate voltage-frequency ratio control, leading to suboptimal operation.
Innovation Solution
A motor control apparatus that divides motor current into torque and excitation currents, using a secondary-magnetic-flux-command calculating unit and PWM-signal generating unit to perform vector control, minimizing current root-mean-square values and optimizing secondary magnetic flux commands to reduce copper and iron losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If V/F fixing control is used to simplify control structure, then control complexity is reduced, but motor loss increases in low-speed or light-load regions
Solution Approach 1:
The patent dynamically adjusts the voltage-frequency ratio based on rotational speed and load conditions. Instead of fixing V/f throughout all operating ranges, the control unit varies the ratio to match actual motor needs, reducing excessive voltage application in low-speed/light-load regions while maintaining simplicity of V/F control structure
Solution Approach 2:
The invention changes the voltage-frequency ratio parameter according to operating conditions. By calculating optimal V/f ratios based on rotational speed and load torque, the system adapts voltage and frequency parameters dynamically, reducing motor losses without requiring complex control architecture
2Adaptability or versatility
If arithmetic processing using numerical formula is performed in all speed regions, then control coverage is complete, but calculation complexity increases
Solution Approach 1:
The patent segments the speed range into multiple regions (low-speed region, medium-speed region, high-speed region) and applies different control strategies to each segment. This reduces calculation complexity within each region while maintaining complete control coverage across all operating ranges
Solution Approach 2:
The control system dynamically selects appropriate control methods based on the current operating region. By transitioning between different control approaches (V/F fixing in some regions, numerical formula in others), the system maintains versatility without requiring complex calculations in all regions simultaneously
Data Source
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AI summary
A motor control apparatus includes a secondary-magnetic-flux-command calculating unit 5 including a minimum-current-secondary-magnetic-flux-command calculating unit that calculates a secondary magnetic flux command F2R for minimizing a current root-mean-square value due to a torque current and an excitation current and a PWM-signal generating unit 9 that generates a torque current command for outputting a desired torque command PTR and an excitation current command for outputting the secondary magnetic flux command F2R, performs vector control such that a q-axis current I1QF, which is a detection value of the torque current, and a d-axis current I1DF, which is a detection value of the excitation current, respectively coincide with the torque current command and the excitation current command, and generates control signals U, V, W, X, Y, and Z for turning on and off a switching element 16 included in an inverter 11.