Brushless Motor Thermal Shock Prevention via Adaptive Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushless motors face damage when started at low temperatures due to thermal shock, and existing preheating methods are costly and inefficient.
Innovation Solution
A method of controlling a brushless motor by sensing temperature to set a lower current limit, sequentially energizing and de-energizing the winding, and gradually increasing the current limit as temperature rises, while maintaining the rotor at a fixed position to minimize thermal shock and reduce power input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor is driven at high current and power at low temperatures, then the motor can deliver full performance, but thermal shock damages motor components
Solution Approach 1:
The control system performs preliminary heating action before full operation by sequentially energizing and de-energizing windings at reduced current levels, gradually raising motor temperature to prevent thermal shock during subsequent high-power operation
Solution Approach 2:
The control system applies periodic energizing and de-energizing cycles to the motor windings, creating controlled thermal cycles that gradually heat the motor without causing thermal shock, enabling safe operation at low temperatures
2Object-affected harmful factors
If a heating device is added to preheat the motor, then thermal shock damage is prevented, but the motor cost increases
Solution Approach 1:
The motor uses its own windings and control system to generate controlled heating during operation, eliminating the need for external heating devices and reducing overall system cost while still preventing thermal shock damage
Solution Approach 2:
The motor windings serve dual functions: both as operational components for generating motor force and as heating elements for preheating the motor, eliminating the need for separate heating devices
3Temperature
If the current limit is increased to achieve faster heating, then heating rate improves, but thermal shock risk increases
Solution Approach 1:
The control system dynamically adjusts the current limit based on real-time temperature feedback, increasing current limit as temperature rises to maintain optimal heating rate while preventing thermal shock through adaptive 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 prevents damage from thermal shock, reduces power consumption, and allows for safe motor operation at lower temperatures without the need for additional heating devices, achieving efficient heating while maintaining component safety.
Implementation Method 1
By sequentially energizing and de-energizing a phase winding, power losses (e.g. copper losses, iron losses and switch losses) act to heat the motor
Data Source
AI summary
A method of controlling a brushless motor that includes sensing a temperature and using the sensed temperature to define a current limit. A lower current limit is then defined for a lower sensed temperature. A winding of the motor is sequentially energized and de-energized, with the winding being de-energized when current in the winding exceeds the defined current limit.