Pole-Change Induction Motor for Ram Air Fan Weight Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ram air fan systems with induction motors face inefficiencies and weight issues due to excessive magnetizing current and low power factor when operating at low speeds, requiring large and heavy contactors and motor controllers.
Innovation Solution
A pole-change induction motor system with separate conductor buses and controllers for high and low-speed operations, utilizing YY/Y or YY/Δ configurations to maintain similar frequencies and voltages, reducing magnetizing current and enabling smaller, lighter motor controllers and contactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the ram air fan motor operates at low speed and low terminal voltage, then the speed and power are reduced, but the magnetizing current becomes excessively high relative to load current, resulting in very low power factor and reduced efficiency
Solution Approach 1:
The patent applies parameter changes by switching between different pole-count configurations (first and second pole counts) of the induction motor. This changes the motor's electrical parameters including synchronous speed, impedance, and current characteristics. By selecting appropriate pole counts for different operating conditions, the system maintains better power factor and efficiency across both high and low speed operations, avoiding the excessively high magnetizing current that would otherwise occur at low speeds with a fixed pole configuration.
2Speed
If the ram air fan motor operates at low speed and low terminal voltage, then the speed is reduced, but the efficiency of the motor and motor controller is reduced
Solution Approach 1:
The patent uses parameter changes through pole-count switching to optimize motor efficiency across different speed ranges. By changing the pole count configuration, the motor operates at or near its optimal efficiency point for each speed condition, rather than operating inefficiently at low speeds with a fixed pole configuration. This maintains better overall system efficiency while providing variable speed operation.
3Speed
If the low power factor and low terminal voltage operating condition is used, then the motor can operate at low speed, but a relatively large rating and weight is required for the contactor
Solution Approach 1:
The patent applies parameter changes by switching pole counts to improve power factor at low speed operation. This reduces the current magnitude and improves the power factor, thereby reducing the electrical stress on the contactor. As a result, a smaller and lighter contactor rating becomes sufficient, reducing the weight of stationary objects in the system while still enabling low-speed motor operation.
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 system achieves reduced weight and increased efficiency by optimizing motor configurations for both high and low-speed operations, necessitating smaller contactors and controllers, while maintaining consistent operating frequencies and voltages.
Implementation Method 1
a pole-change induction motor with at least two pole-count configurations
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A ram air fan control system (700;800) includes a ram air fan motor (703;803), the ram air fan motor being a pole-change induction motor (401;501) with at least two pole-count configurations; a ram air fan contactor (711;811,805) in operative communication with a first pole-count configuration of the ram air fan motor over a conductor bus (712,822); a ram air fan power controller (701,801) in operative communication with the ram air fan contactor; a common contactor (721;821,806) in operative communication with a second pole-count configuration of the ram air fan motor over a second conductor bus (722) or the conductor bus (822); and a common power controller (702,802) in operative communication with the common contactor (721;821,806).