Motor Driving Device Switching Winding via Zero Voltage Circulating Current
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Solution Overview
Problem
Conventional motor driving devices experience failures due to arc discharge and wear at the contact points of the connection switcher when switching the connection condition of a motor's stator winding during rotating operations, as the potential difference causes issues with the contact points of the switch.
Innovation Solution
A motor driving device that incorporates an electromagnetic contactor, an inverter, and a short-circuiting circuit with a rectification circuit and switch, which allows the connection switcher to switch the winding condition when the output voltage of the inverter is zero, creating a circulating current that prevents current flow through the contactors, thus avoiding arc discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the connection switcher switches the connection condition of the winding during the rotating operation of the motor, then the motor can operate continuously without stopping, but arc discharge occurs between the contact points of the switch due to potential difference, causing wear and fusion of the contact points
Solution Approach 1:
A diode is introduced as an intermediary component between the connection switcher and the motor winding. The diode conducts current in one direction only, allowing current to flow through the winding during motor operation while preventing reverse current that would cause arc discharge at the switch contact points. This mediator protects the switch from wear and fusion while enabling continuous motor operation.
Solution Approach 2:
The invention converts the harmful effect of current flow during switching into a beneficial protection mechanism. By allowing current to circulate through the diode and winding during operation, the system prevents arc discharge at the switch contact points. The current that would normally cause wear is redirected through the diode, transforming a harmful effect into a protective mechanism that extends switch life.
2Reliability
If the output voltage of the inverter is controlled to make the current flowing to the motor equal to zero for switching, then the connection condition can be switched, but this requires stopping the motor or reducing speed, which reduces productivity
Solution Approach 1:
The diode enables continuous current flow through the motor winding during the switching operation. Instead of requiring the motor to stop or the current to be reduced to zero, the diode maintains a continuous circulation path for the current. This allows the switching operation to proceed without interrupting the motor's useful action, maintaining productivity while ensuring reliable switching.
Solution Approach 2:
The diode is pre-installed in the circuit to establish a predetermined current path before switching occurs. This preliminary arrangement of the current circulation path through the diode and winding ensures that when switching is needed, the current can immediately redirect through the safe path without requiring motor shutdown or complex control sequences.
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 failures in the connection switcher during motor operation by eliminating arc discharge and wear, enabling seamless switching of the connection condition without stopping the motor, even at high speeds, and extends the lifespan of the switch components.
Implementation Method 1
an electromagnetic contactor connected to a winding of a motor and switches connection condition of the winding by switching condition of the electromagnetic contactor
Implementation Method 2
a short-circuiting circuit having a rectification circuit and a switch
Data Source
AI summary
A motor driving device includes: a connection switcher that has an electromagnetic contactor connected to a winding of a motor and switches connection condition of the winding by switching condition of the electromagnetic contactor; an inverter to apply an output voltage as an AC voltage to the winding via the connection switcher; a short-circuiting circuit having a rectification circuit and a switch; and a controller to control the electromagnetic contactor, the inverter and the switch, wherein a circulating circuit is formed by the short-circuiting circuit and the winding when the switch is set at ON, and the connection switcher switches the connection condition of the winding in a period in which the output voltage of the inverter is set at zero in a rotating operation of the motor and a current caused by the rotating operation circulates in the circulating circuit.