BLDC Motor Multi-Pulse Commutation for Lower EMI and Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor control technologies for brushless DC motors face challenges in reducing power dissipation, heating, switching losses, electromagnetic interference (EMI), audible noise, and noise associated with high current, particularly in single-pulse and pulse width modulation (PWM) control methods.
Innovation Solution
A motor controller system that employs adaptive multi-pulse commutation, utilizing a commutation monitor, pulse scheduler, and driver controller to optimize pulse timing and field direction switching within the commutation cycle, based on position data and rotational speed, to minimize peak current and switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-pulse commutation is used, then device complexity is reduced, but power dissipation and heating increase due to higher current
Solution Approach 1:
The single commutation pulse is segmented into multiple pulses (first pulse and second pulse) distributed across the commutation cycle. This segmentation reduces the peak current required for each individual pulse while maintaining the total energization time, thereby reducing power dissipation and heating in the winding without significantly increasing control circuit complexity
Solution Approach 2:
The invention applies periodic multi-pulse commutation where multiple pulses are delivered at specific intervals within the commutation cycle rather than a single continuous pulse. This periodic action allows the current to decay between pulses, reducing instantaneous power dissipation and heating while maintaining motor drive capability
2Loss of energy
If PWM control is used, then power dissipation is reduced, but switching losses and EMI increase
Solution Approach 1:
The multi-pulse commutation scheme uses naturally occurring commutation cycle timing to deliver pulses at optimal moments, avoiding the high-frequency switching inherent in PWM. This reduces switching losses and electromagnetic interference while maintaining effective power delivery to the motor winding
Solution Approach 2:
The first pulse is delivered at a predetermined time within the commutation cycle to initiate current flow and begin the energization process before the second pulse. This preliminary action allows the motor to respond to the first pulse while the second pulse reinforces the effect, achieving effective motor control with lower peak currents and reduced switching stress
3Power
If higher current is used, then motor power output increases, but audible noise and EMI increase
Solution Approach 1:
The total current requirement for motor power output is segmented across multiple pulses rather than delivered in a single high-current pulse. This segmentation reduces peak current while maintaining total energy delivery, thereby reducing audible noise and electromagnetic interference associated with high current transients
Solution Approach 2:
Multiple pulses are delivered at periodic intervals within the commutation cycle, allowing current to decay to lower levels between pulses. This periodic delivery maintains average power output while reducing peak current levels, thereby minimizing audible noise and EMI generated by high current
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 adaptive multi-pulse control reduces power dissipation, heating, EMI, and audible noise while maintaining efficiency, achieving similar power consumption to PWM control with lower-cost circuitry and reduced noise.
Implementation Method 1
receive position data from a position sensor coupled to the brushless direct current motor and determine a rotational speed of the brushless direct current motor based on the position data
Implementation Method 2
voltage is applied to the winding and commutated such that the stator poles of the motor pull and push rotor magnets to create rotation
Implementation Method 3
switch a field direction of the winding in response to an end of the commutation cycle
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A control system includes a motor controller coupled to a brushless direct current motor. The motor controller determines a first start time and a first duration for a first pulse and a second start time and a second duration for a second pulse relative to a commutation cycle of the motor. The motor controller energizes a winding of the motor with the first pulse and the second pulse within the commutation cycle.