Motor Winding Connection Switching to Prevent Arcing in Rotation
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Solution Overview
Problem
Existing motor driving apparatuses face challenges in preventing increased apparatus size while switching motor windings during operation, particularly when handling large currents, which affects efficiency and reliability.
Innovation Solution
A motor driving apparatus comprising a DC power supply circuit, an inverter, and a connection switching device that adjusts the motor's winding connection from a first state to a second state with a higher output voltage and rotational speed, ensuring the current remains below a predetermined threshold during switching, allowing for seamless connection switching without arcing or sudden rotational speed changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preparatory loads are connected in parallel with windings to prevent large current flow during switching, then current protection is improved, but apparatus size increases due to increased power capacity requirements
Solution Approach 1:
The patent applies preliminary action by increasing the DC link voltage before switching operations to ensure that current remains below predetermined thresholds during connection changes. The control unit raises the DC link voltage to a higher level prior to switching, which limits the inrush current and eliminates the need for additional preparatory loads, thereby preventing apparatus size increase while maintaining reliable current protection.
2Productivity
If connection switching is performed while motor is rotating to maintain continuous operation, then productivity is improved, but reliability deteriorates due to arcing and sudden rotational speed changes
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the DC link voltage level during switching operations. The control unit increases the DC link voltage to a predetermined higher level during the switching process, which changes the electrical parameters to limit current flow and prevent arcing. This allows connection switching to be performed while the motor is rotating without causing sudden rotational speed changes or reliability issues.
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 solution prevents apparatus size increase, reduces arcing and noise, maintains efficient operation, and allows for reliable switching of motor windings while minimizing current changes, thereby enhancing the motor driving apparatus's reliability and efficiency.
Implementation Method 1
a DC power supply circuit to apply a DC voltage of variable voltage value to DC buses
Implementation Method 2
an inverter to receive the DC voltage on the DC buses and apply an AC voltage of variable frequency and variable voltage value to a motor
Implementation Method 3
a connection switching device to switch connection of windings of the motor
Data Source
AI summary
In a motor driving apparatus including a DC power supply circuit of variable output voltage value, an inverter of variable frequency, and a connection switching device for selecting connection, switching of the connection switching device is performed in a state where an output voltage of the DC power supply circuit is increased, a rotational speed of a motor is increased, and a current flowing through the motor is made not greater than a predetermined threshold. For example, the switching of the connection switching device is performed in a state where the current through the motor is made zero. For example, the switching is performed in a state where the output voltage of the DC power supply circuit is set at a value corresponding to the rotational speed of the motor during the switching. It is possible to prevent increase in apparatus size and switch the connection of windings while the motor is rotating.