DC Brushless Motor Current Spike Control via Position-Based Limit Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
DC brushless motors experience current and voltage spikes when the rotor approaches the aligned position, leading to inefficiencies and potential damage due to the sudden change in current direction.
Innovation Solution
A control strategy is implemented that includes a power supply circuit, a position sensor, and a control circuit to detect the rotor's position and adjust the peak current limit, reducing the current spike by altering the power supply's output when the rotor is close to alignment, thereby minimizing voltage spikes on the input capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the current direction is changed when the rotor passes the aligned position, then the rotor can rotate with fixed direction, but current and voltage spikes occur causing inefficiencies and potential damage
Solution Approach 1:
The control circuit detects when the rotor is approaching the aligned position using position sensor signals, and proactively adjusts the current limit before the commutation event occurs. This preliminary action prevents the harmful current spike from occurring in the first place, rather than reacting after the spike has already damaged the system.
Solution Approach 2:
The patent dynamically changes the current limit parameter based on the rotor's position relative to the aligned position. When the rotor is detected to be within a predetermined angle range of the aligned position, the current limit is reduced from its normal value to a lower value, thereby preventing the conditions that lead to current and voltage spikes during commutation.
2Object-affected harmful factors
If the current limit is reduced when the rotor is close to the aligned position, then current and voltage spikes are decreased, but the motor torque is reduced during this transition period
Solution Approach 1:
The current limit is not statically fixed but dynamically adjusted based on real-time rotor position feedback. The system transitions between two current limit states (normal and reduced) depending on whether the rotor is within the critical angle range of the aligned position, optimizing both protection and performance at different operational phases.
Solution Approach 2:
The current limit reduction is applied periodically only during the specific transition phase when the rotor approaches and passes through the aligned position. During the majority of the rotation cycle where no commutation is imminent, the full current limit is maintained to ensure optimal torque production and motor performance.
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 control strategy effectively decreases current and voltage spikes, maintaining motor stability and preventing damage by adjusting the current limit before the rotor reaches the aligned position, ensuring a smoother operation and reduced stress on the system.
Implementation Method 1
The position sensor may be a hall sensor. According to the right-hand rule, when the current Ic flows through the coil 101 with the direction shown in FIG. 1, there will be a electromagnetic field with an N (north) magnetic pole above and an S (south) magnetic pole below.
Implementation Method 2
when the current Ic flows through the coil 101 with the direction shown in FIG. 1, there will be a electromagnetic field with an N (north) magnetic pole above and an S (south) magnetic pole below. According to the law of opposite magnet poles attract but like magnet poles repel each other, the magnetic torque generated by the electromagnetic field will force a counterclockwise rotation spin of the rotor 102.
Implementation Method 3
According to Lenz's law, the magnitude of the induced electromotive force Vt is proportional to the product of the speed of the rotor and the variation rate dB/dt of the flux density.
Data Source
AI summary
A DC brushless motor system is disclosed. When a rotor of the DC brushless motor is close to an aligned position, there will be current spike in the coil and voltage spike in an input capacitor. By decreasing the peak current limit of the current in the coil when the rotor is close to the aligned position, the current spike and the voltage spike are reduced.