Washing Drum Imbalance Detection Using Motor Phase Current
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Solution Overview
Problem
Existing methods for determining the imbalance in a laundry drum of a washing machine during a spin cycle are imprecise due to the influence of inverter losses and AC supply voltage fluctuations, which affect the accuracy of power consumption calculations.
Innovation Solution
Measuring the phase current of the drive motor and calculating the imbalance based on actual power consumption, excluding inverter losses and AC supply voltage fluctuations, while accounting for initial load and energy delivered during the spin operation to distinguish between torque due to initial load and imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power consumption is calculated from DC link voltage and DC link current, then power consumption can be determined, but the determination of imbalance becomes imprecise due to inverter losses and AC supply voltage fluctuations
Solution Approach 1:
The patent extracts the measurement point from the DC link (where inverter losses affect accuracy) to the motor terminal (where actual motor power consumption is measured). By measuring phase currents and voltages directly at the motor, the method separates motor consumption from inverter losses, enabling precise imbalance determination without being affected by energy losses in the inverter.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using phase current measurements combined with motor parameters to calculate motor power consumption. This intermediary method bypasses the need to directly measure DC link parameters and eliminates the influence of inverter losses and AC supply fluctuations on the imbalance determination.
2Measurement precision
If DC link current is measured to determine power consumption, then power can be calculated, but AC supply voltage fluctuations affect the accuracy of imbalance determination
Solution Approach 1:
The patent extracts the measurement from the AC supply side (where voltage fluctuations occur) to the motor terminal side. By measuring phase currents and using motor parameters to calculate power, the method isolates motor consumption from AC supply variations, eliminating the harmful effect of voltage fluctuations on imbalance determination accuracy.
Solution Approach 2:
The patent implements feedback by continuously monitoring phase currents and using them to calculate real-time motor power consumption. This feedback mechanism allows the system to compensate for any variations and accurately determine imbalance based on actual motor consumption, independent of AC supply voltage fluctuations.
3Power
If inverter losses are included in power consumption calculation, then total power can be determined, but the actual motor power and thus the imbalance cannot be determined precisely
Solution Approach 1:
The patent extracts the calculation basis from total system power (including inverter losses) to motor-only power. By measuring phase currents at the motor terminal and using motor parameters, the method directly calculates motor power consumption, separating it from inverter losses. This extraction enables precise determination of actual motor power for accurate imbalance assessment.
Solution Approach 2:
The patent introduces an intermediary calculation method that uses phase current measurements and motor parameters as intermediaries to determine motor power. This approach bypasses the need to account for inverter losses separately, as the intermediary measurements directly reflect motor consumption, enabling precise imbalance determination.
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 provides a precise and robust method for determining the imbalance, allowing for accurate control of the spin operation and preventing uncontrolled vibrations by adjusting the spin speed based on the degree of imbalance detected.
Implementation Method 1
An electrical phase current is measured in at least one phase phase of the stator
Data Source
Figure 1
Figure 2~3
AI summary
An imbalance in a washing drum 3 of a washing machine 1 is intended to be determined during a spin dryer mode. A method is provided in which the washing drum 3 is driven by a drive motor 5. An electrical AC voltage U12, U23, U13 is provided by means of an inverter 26 for each of the phases 7, 8, 9 of the drive motor 5, specifically from an intermediate-circuit DC voltage Uz. An electrical line current l1, I2, I3 is determined in at least one of the phases 7, 8, 9. In addition, even before the initiation of the spin dryer mode, an initial load in the washing drum and/or an amount of energy are/is determined, which amount of energy is that emitted to the drive motor, and is integrated during, in particular since the start of, a washing process prior to the spin dryer mode. The imbalance is determined as a function of measured values for this line current I1, I2, I3 and as a function of the initial load and/or the energy integrated during the washing process. In particular, a profile of electrical energy E which has been emitted since the start of the spin dryer mode to the drive motor 5 can be determined over the time t, and a gradient ?E/?t of this profile V1, V2 can be used as the basis to determine the imbalance. A corresponding drive apparatus 2 as well as a washing machine 1 are also provided.