Electric Drive Startup Control Under Low Supply Voltage
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Solution Overview
Problem
Household appliances with electric drives face issues in starting efficiently due to fluctuating supply voltages, leading to insufficient energy supply and potential false starts, especially when the voltage is below the nominal level.
Innovation Solution
A controller in the household appliance selects and executes pre-stored starting processes based on voltage values, using a rectifier, smoothing capacitor, and inverter circuit to manage energy efficiently, allowing for either full or reduced starting currents, and optionally recharging the smoothing capacitor to ensure reliable drive startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high starting current is supplied to the electric drive to ensure sufficient torque for starting, then the starting reliability is improved, but the energy loss increases and the smoothing capacitor discharges excessively
Solution Approach 1:
The patent applies dynamics by making the starting process adaptive rather than static. The control system dynamically selects between a first starting process (with rotor positioning and high starting current) and a second starting process (without positioning and with reduced starting current) based on the detected voltage value. This dynamic adaptation allows the system to optimize between starting reliability and energy loss depending on available voltage, preventing unnecessary energy discharge when full power is not required.
Solution Approach 2:
The patent changes the operating parameters of the electric drive based on voltage conditions. When voltage is below nominal, the system switches to the second starting process with reduced starting current and skips rotor positioning. This parameter change adapts the starting characteristics to match available voltage, preventing excessive capacitor discharge and energy loss while maintaining sufficient torque for starting under reduced voltage conditions.
2Productivity
If the rotor is positioned before starting the electric drive, then the starting efficiency is improved, but the starting time increases and the process becomes more complex
Solution Approach 1:
The patent makes the rotor positioning step dynamic rather than mandatory. The control system evaluates the detected voltage value and dynamically decides whether to execute the positioning sequence before starting. When voltage is sufficient, positioning is performed for optimal starting efficiency. When voltage is below nominal, positioning is skipped to reduce starting time and complexity, and the system proceeds directly to energizing the motor with reduced current.
Solution Approach 2:
The patent segments the starting process into distinct phases: rotor positioning (optional) and motor energization. By making the positioning phase optional and separable, the system can selectively apply it based on voltage conditions. This segmentation allows the starting process to be simplified when full efficiency is not critical, while maintaining the option for optimized starting when voltage conditions permit.
3Adaptability or versatility
If multiple starting processes are available for selection, then the adaptability to different voltage conditions is improved, but the device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-programming multiple starting processes in the control unit before operation. The first starting process includes rotor positioning followed by energization with nominal or maximum starting current. The second starting process is pre-configured to energize the motor directly with reduced starting current without positioning. When voltage fluctuation is detected, the control system simply selects between these pre-prepared sequences, avoiding the need to create control logic in real-time and reducing operational complexity while maintaining high adaptability.
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 prevents unnecessary energy losses and false starts by optimizing the starting process according to available voltage, ensuring the electric drive can be started efficiently even at lower voltages, reducing energy wastage and maintaining appliance functionality.
Implementation Method 1
The power supply includes a rectifier and a smoothing capacitor downstream of the rectifier
Implementation Method 2
The power supply includes a rectifier and a smoothing capacitor downstream of the rectifier
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a domestic appliance (100) having an electric drive, a voltage supply (109) for supplying the actuator (112) to which an electric drive is connected downstream and which has an electric supply voltage, and a controller (111) for controlling the electric drive (102), wherein the controller (111) is designed to measure a voltage value of the supply voltage and, if the voltage value reaches a threshold value, to start the electric drive (102) in accordance with a first starting procedure or, if the voltage value falls below the threshold value, to start the electric drive (102) in accordance with a second starting procedure.