Electric Motor Input Power Estimation Without Sensors
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Solution Overview
Problem
Existing methods for determining the input power of electric motors, such as using current and voltage sensing circuitry, are costly and complex, making them impractical for low-cost motor applications.
Innovation Solution
A motor assembly comprising an electric motor and a motor controller that estimates input power by determining output power, motor speed, and calculating a scaling factor to estimate input power without the need for current and voltage sensing circuitry, using equations like input power=(−K1X2+K2X+K3) times output power, where K1, K2, and K3 are constants and X is the motor speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current and voltage sensing circuitry is used to determine input power, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the essential information needed for power estimation (current and voltage magnitudes) and obtains them indirectly through alternative measurement methods rather than using traditional sensing circuitry. The controller estimates input power by measuring other parameters and calculating accordingly, removing the need for dedicated current and voltage sensors.
Solution Approach 2:
The patent creates a mathematical model that copies the relationship between electrical parameters and power consumption. By measuring easily obtainable parameters like motor speed, torque, and electrical characteristics, the system replicates the information that would be obtained from direct sensing, allowing power estimation without physical sensors.
2Measurement precision
If current and voltage sensing circuitry is used to determine input power, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the expensive sensing circuitry components from the motor system while retaining the ability to estimate input power accurately. By extracting only the necessary measurement information through alternative means (measuring motor speed, torque, and electrical characteristics), the system achieves power measurement functionality without the high manufacturing cost of additional sensors.
Solution Approach 2:
The patent replaces expensive, complex sensing circuitry with a cost-effective computational approach using existing motor controller resources. The estimation method uses readily available measurements and mathematical calculations that are already part of the motor control system, eliminating the need for additional expensive hardware components.
3Productivity
If speed sensing is implemented, then productivity is improved through better control, but device complexity increases
Solution Approach 1:
The motor controller performs speed estimation using its own existing measurements of electrical characteristics and motor parameters. The system uses its built-in capability to measure stator current frequency and other electrical parameters to determine motor speed, eliminating the need for external speed sensors while maintaining accurate speed information for control purposes.
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 accurate estimation of input power without additional hardware, reducing costs and complexity, and is applicable to various motor technologies and applications like HVAC systems and washing machines.
Implementation Method 1
The speed of the motor may be sensed with a Hall effect sensor or other shaft speed sensor.
Data Source
AI summary
A method of estimating an input power of a motor comprises determining an output power of the motor; determining a speed of the motor; calculating a scaling factor as a function of the speed of the motor; and estimating the input power as a function of the scaling factor and the output power.