Electric Motor Thermal Derating via Dynamic Power Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for limiting the temperature in electric machines often require overdesigning to handle short-term power peaks, leading to increased costs, space, and weight, as they do not effectively allow for temporary exceedance of continuous temperature limits without risking damage.
Innovation Solution
A method that allows temporary exceedance of continuous temperature limits by calculating a derating time during which additional heat can be absorbed, followed by reducing power and torque to prevent long-term damage, using temperature-sensitive elements and a controller to manage the temperature difference and heat absorption characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric motor is designed to meet maximum short-term power requirements, then the continuous power rating must be increased, but this leads to increased costs, installation space, and weight
Solution Approach 1:
The patent applies dynamic derating strategies that adjust the continuous power rating based on real-time temperature conditions and predicted future temperatures. The system dynamically determines a derated continuous power rating that varies with operating conditions, allowing the motor to operate at higher power levels when temperatures permit and reduce power when temperatures approach limits. This dynamic adjustment eliminates the need to design for maximum continuous power, reducing motor size, weight, and cost while maintaining the capability to deliver maximum power for short periods when needed.
2Power
If the electric motor is designed to meet maximum short-term power requirements, then the continuous power rating must be increased, but this leads to increased installation space
Solution Approach 1:
The patent applies dynamic derating strategies that adjust the continuous power rating based on real-time temperature conditions and predicted future temperatures. The system dynamically determines a derated continuous power rating that varies with operating conditions, allowing the motor to operate at higher power levels when temperatures permit and reduce power when temperatures approach limits. This dynamic adjustment eliminates the need to design for maximum continuous power, reducing motor size, weight, and cost while maintaining the capability to deliver maximum power for short periods when needed.
3Reliability
If active derating is applied to prevent thermal overloading, then the torque or phase current is reduced, but this prevents the motor from delivering maximum power during short-term peaks
Solution Approach 1:
The patent applies preliminary action by predicting future temperature development before thermal limits are exceeded. The system uses predicted temperature data to proactively adjust the continuous power rating and operating parameters in advance, preventing thermal overload while maximizing power delivery during the predicted safe operating window. This allows the motor to deliver maximum power during short-term peaks when temperature predictions indicate safety, while still protecting against thermal overload through advance derating when predictions indicate risk.
Solution Approach 2:
The patent applies feedback by continuously monitoring actual temperature, comparing it with predicted temperature, and using this information to dynamically adjust the continuous power rating and operating parameters. The feedback loop enables the system to distinguish between temporary temperature excursions that are safe and those that indicate impending thermal overload, allowing maximum power delivery when safe and appropriate derating when necessary, thus resolving the contradiction between reliability and short-term power capability.
4Duration of action of stationary object
If a fixed continuous power rating is used, then the motor can operate continuously at that power level, but it cannot accommodate short-term power peaks without overdesign
Solution Approach 1:
The patent applies dynamic derating strategies that adjust the continuous power rating based on real-time temperature conditions and predicted future temperatures. The system dynamically determines a derated continuous power rating that varies with operating conditions, allowing the motor to operate at higher power levels when temperatures permit and reduce power when temperatures approach limits. This dynamic adjustment enables both continuous operation at appropriate power levels and short-term power peaks when temperature conditions allow, eliminating the need for fixed overdesign ratings.
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
Enables higher power outputs for short durations without permanent damage, allowing for a more compact and cost-effective electric drive design by strategically managing temperature and power reduction.
Implementation Method 1
determined on the basis of a temperature of the electric machine
Implementation Method 2
Losses caused by the ohmic resistance of the stator windings contribute to the temperature development in an electric motor to a large extent
Data Source
Figure 1
Figure 2~3
AI summary
In order to provide a method for limiting the temperature in an electrical machine, wherein the retrieval of higher drive powers is briefly allowed after a predetermined permanent temperature has been exceeded, it is proposed to determine the temperature φ in the electrical machine, to allow a further temperature increase in a period calculated by a controller after a predetermined permanent temperature φDauer has been exceeded and to reduce the power and/or the torque and/or at least one phase current of the electrical machine after expiry of this period. In order to briefly achieve higher drive powers of an electrical machine, exceeding of the permanent temperature φDauer is allowed for an implicitly or explicitly defined limited duration and the torque, the power and/or at least one phase current of the electrical machine is/are reduced uniformly (that is to say not abruptly) after expiry of this time.