BLDC Motor Coil Preheating for Low Temperature Start-Up
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Solution Overview
Problem
BLDC motors experience unreliable start-up behavior at low temperatures, particularly below -40°C, due to increased viscosity of the lubricant in the motor bearings, leading to higher friction loads and reduced torque, which existing solutions often address through overdesigning the drive circuit or repeated start-up attempts without effectively addressing the viscosity issue.
Innovation Solution
A method and system that includes a motor drive circuit with a timer unit and energizing unit to preheat the coils before starting the motor, using a special energizing scheme with alternating pulses to heat up the lubricant indirectly, thereby reducing viscosity and improving start-up reliability without increasing system cost or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive circuit is overdesigned to provide higher torque capability, then the motor can start reliably at low temperatures, but the system cost and complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-heating the motor coils before starting the motor at low temperatures. The drive circuit detects low temperature conditions and activates a pre-heating phase where current is applied to the coils to generate heat, warming the lubricant before the motor actually starts rotating. This preliminary thermal preparation reduces the viscosity of the lubricant in advance, enabling reliable start-up without requiring an overdesigned drive circuit with excessive torque capability.
2Reliability
If the drive circuit is overdesigned to provide higher torque capability, then the motor can start reliably at low temperatures, but the system cost increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the drive circuit's operating parameters based on temperature conditions. At low temperatures, the circuit transitions from a standard driving mode to a pre-heating mode with different current characteristics and timing. The drive circuit includes temperature detection capability and modifies its output parameters (current magnitude, pulse width, frequency) to provide appropriate pre-heating energy. This allows the same drive circuit to serve both normal operation and cold-start requirements without overdesigning for the worst-case scenario, thereby reducing system cost while maintaining reliability.
3Reliability
If repeated start-up attempts are made without addressing viscosity, then the motor may eventually start, but time is lost and reliability is reduced
Solution Approach 1:
The patent applies preliminary action by implementing a pre-heating phase before the actual motor start attempt. When low temperature is detected, the drive circuit first applies current to the coils to heat the lubricant, reducing its viscosity before the motor is commanded to start. This preliminary thermal preparation eliminates the need for repeated start-up attempts, as the motor is guaranteed to have sufficient torque capability from the first attempt. The process sequentially executes pre-heating followed by start-up, ensuring reliable operation without time loss from multiple failed attempts.
4Device complexity
If standard energizing schemes are used at low temperatures, then the drive circuit remains simple, but the motor fails to start reliably due to high friction
Solution Approach 1:
The patent applies dynamics by making the drive circuit's energizing scheme adaptive rather than static. The circuit dynamically adjusts its operation based on detected temperature conditions. At low temperatures, it automatically transitions to a pre-heating energizing mode with different parameters (higher current, extended duration, specific pulse patterns) before normal operation. This dynamic adaptation allows the simple drive circuit to provide enhanced pre-heating capability when needed, resolving the contradiction between simplicity and reliability by making the circuit's behavior conditional rather than fixed.
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 preheating method enhances the motor's start-up reliability at low temperatures by reducing the viscosity of the lubricant, allowing the motor to start successfully even with limited torque capability, without the need for overdesigning the drive circuit or repeated start-up attempts.
Implementation Method 1
preheating the coils before starting the motor, using a special energizing scheme with alternating pulses to heat up the lubricant indirectly
Data Source
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AI summary
A method of starting and/or driving a fan assembly (110), the fan assembly comprising a BLDC motor (111) having one or more coils (112), and a bearing (113) comprising a lubricant. The method comprises performing a special action for intentionally heating up the one or more coils (112) and thereby indirectly heating up the lubricant. The method may comprise measuring a temperature of the bearing, or measuring a value related to said temperature, and performing the special action only if said temperature is below a certain threshold temperature.