Brushless DC Motor With Switchable Stators
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Solution Overview
Problem
Conventional brushless direct current (BLDC) motors face a challenge in maintaining starting torque while increasing vehicle speed, as the voltage and torque constants must decrease to remain within the power supply voltage limit, leading to reduced starting torque at higher speed capabilities, and existing solutions like mechanical transmissions add weight, cost, and efficiency losses.
Innovation Solution
The use of independently driven and switchable stators in a BLDC motor, with separate power electronics directing energy to each stator, allowing for adjustments in torque and speed within the voltage limit by switching between series and parallel connections, utilizing unidirectional power switches like MOSFETs and IGBTs to manage current direction cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the voltage and torque constants are decreased to remain within the power supply voltage limit, then the vehicle speed capability is increased, but the starting torque is reduced
Solution Approach 1:
The motor is divided into multiple independent stators (first stator, second stator, etc.) that can be independently controlled by separate power electronics. This segmentation allows the motor to operate in different configurations: at low speeds, multiple stators work together to provide high starting torque; at high speeds, individual stators can be switched independently to maintain voltage within power supply limits while achieving high vehicle speed capability.
Solution Approach 2:
The motor employs dynamic switching of stator connections through separate power electronics for each stator. The stators can be switched between series and parallel connections based on operating conditions. This dynamic reconfiguration allows the motor to adapt its voltage and torque constants in real-time, maintaining high starting torque when needed while achieving high speed capability when required, all within the power supply voltage limit.
2Speed
If a mechanical transmission with two or more speeds is employed, then the vehicle speed range is extended, but the weight, cost and efficiency losses increase
Solution Approach 1:
The patent replaces the mechanical transmission system with an electrical control system. Instead of using mechanical gears and transmissions to achieve different speed ranges, the invention uses independent power electronics for each stator to dynamically control motor output. This substitution eliminates the need for heavy mechanical transmission components while achieving the same vehicle speed range extension, thereby reducing weight, cost, and efficiency losses associated with mechanical transmissions.
3Speed
If the voltage and torque constants are decreased to remain within the power supply voltage limit, then the vehicle speed capability is increased, but the cost increases due to additional components
Solution Approach 1:
Each independent stator with its dedicated power electronics serves multiple functions: it can operate individually for high-speed low-torque applications, or combine with other stators for low-speed high-torque applications. This multi-functionality allows the system to achieve high vehicle speed capability without requiring completely separate motor systems for different speed ranges, thereby reducing overall manufacturing cost despite the added complexity of independent stator 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 enables the BLDC motor to maintain consistent torque and power output across varying speeds without exceeding the power supply voltage, reducing weight and cost, and improving efficiency by using unidirectional power switches, thus enhancing the motor's performance and reliability.
Implementation Method 1
a first power electronics for directing energy to the first stator, and a second power electronics for directing energy to the second stator
Implementation Method 2
The DC motor employs independently driven and switchable stators. The motor includes at least a first stator and a second stator, positioned for relative rotation with a rotor
Data Source
AI summary
An apparatus and method are provided for adjusting torque and speed of a motor, while remaining within the voltage limit of a power supply. The invention provides a brushless direct current motor with independently driven and switchable stators. In an aspect, each stator and the rotor is structured to function as an independent motor separate from another stator and the rotor. A first power electronics directs energy to a first stator, and a second power electronics directs energy to a second stator. A rotor rotates relative to the stators. In an aspect, a commutation electronics determines electrical position of the rotor relative to the stators, and synchronizes current pulses directed to a sequentially selected phase of the stators, to generate a rotating magnetic field that communicates with the rotor. A controller sets the connection of the first power electronics in series or in parallel with the second power electronics.