Method for identifying the load condition of a pump
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Solution Overview
Problem
Existing household appliance pumps driven by electric motors, such as dishwashers, face challenges in accurately determining their load state due to the expense and difficulty of obtaining information about current load status, especially with single-strand motors connected directly to mains voltage.
Innovation Solution
A three-strand, three-phase, permanently excited synchronous motor is used with field-oriented vector control, employing a pulse width modulated voltage system that can be adjusted in frequency, phase, and amplitude, allowing for the determination of the load state from the torque-forming current component iq through a closed control circuit and motor model feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-strand motor connected directly to mains voltage is used, then the pump structure is simple and cost-effective, but the ability to determine current load status becomes expensive and difficult
Solution Approach 1:
The patent implements feedback by measuring the phase currents of the synchronous motor and using field-oriented vector control to derive the torque-producing current component iq. This current component serves as a direct indicator of the pump's load status, enabling the control system to continuously monitor and respond to load changes without additional sensors on the pump itself.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the electrical current characteristics of the synchronous motor as a mediator to infer the mechanical load status of the pump. Instead of directly measuring pump parameters, the system measures the motor's phase currents and processes them through coordinate transformation to obtain the torque component iq, which indirectly but accurately reflects the pump load.
2Reliability
If the pump continues to run after emptying the appliance, then the pump ensures complete fluid removal, but noise level increases and electrical losses occur
Solution Approach 1:
The system uses feedback from the torque-producing current component iq to detect when the pump transitions from loaded operation to idling. When the pump has emptied the appliance, the load disappears and the iq component drops to zero or near-zero values. The control system monitors this change and automatically switches off the pump, preventing unnecessary energy consumption and noise generation while ensuring complete fluid removal.
3Productivity
If the drain hose is clogged, then the pump continues to operate, but the pump remains ineffective and generates noise without achieving fluid removal
Solution Approach 1:
The system employs feedback monitoring of the current component iq to detect abnormal operating conditions. When the drain hose is clogged, the pump operates under abnormal load conditions that produce characteristic current signatures. The control system analyzes the iq component over time and can distinguish between normal operation, idling, and blocked conditions, enabling timely intervention to stop the pump and prevent noise and energy waste.
4Measurement precision
If a three-phase synchronous motor with field-oriented vector control is used, then the load state can be accurately determined from current components, but the device complexity increases
Solution Approach 1:
The patent uses the electrical current characteristics of the synchronous motor as an intermediary to infer the mechanical load status. By measuring phase currents and processing them through coordinate transformation, the system obtains the torque-producing current component iq, which serves as a precise indicator of pump load. This approach achieves accurate load detection using only electrical measurements, avoiding the need for additional mechanical sensors.
Solution Approach 2:
The patent replaces direct mechanical load sensing with electrical measurement and processing. Instead of using mechanical sensors to detect pump load, the system uses the electrical characteristics of the synchronous motor's current components. The field-oriented vector control transforms the three-phase currents into rotating reference frame components, where the q-component directly represents torque and load information, substituting mechanical measurement with electrical sensing and signal processing.
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 method enables accurate detection of load states, including idling and blockages, reducing noise, conserving energy, and allowing for targeted fluid pumping, while providing error detection and improved operational control of household appliance pumps.
Implementation Method 1
a three-strand, three-phase, permanently excited synchronous motor is used
Implementation Method 2
employing a pulse width modulated voltage system that can be adjusted in frequency, phase, and amplitude
Data Source
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AI summary
The invention relates to a method for identifying the load condition of a fluid-delivering, electric motor driven pump of a domestic appliance. The invention is characterized in that the pump is driven by a permanent magnet electric motor which is designed as a synchronous motor, a torque-producing current component iq being used to determine at least one load condition of the pump.