Motor Drive Switching Control for Power-Loss Arc Prevention
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Solution Overview
Problem
Existing motor driving apparatuses face issues with connection switching devices experiencing arc discharge and breakdown due to power failures, leading to contact welding and reduced reliability, especially when electromagnetic or semiconductor switches are used.
Innovation Solution
A motor driving apparatus with a capacitor to store electric charge, a connection switching device, a control power supply generating circuit, an inverter, and a control device that detects electric quantities to predict voltage falls, initiating a braking process to stop the motor before the switching power supply voltage drops below the minimum required, preventing breakdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electromagnetic switches are used in the connection switching device, then the device can be operated, but arc discharge and contact welding occur when power supply is lost, leading to breakdown
Solution Approach 1:
The control device stops the inverter before the switching power supply voltage falls below the minimum required voltage for the connection switching device operation. This preliminary action prevents the electromagnetic switches from operating in a voltage state that would cause arc discharge and contact welding, thereby maintaining reliability while allowing normal operation.
2Reliability
If the inverter is stopped immediately when power supply is lost, then breakdown is prevented, but the motor continues to rotate at high speed causing contact between rotor and fixed part
Solution Approach 1:
The control device calculates a predetermined voltage threshold that ensures the motor reaches a safe rotation speed before the inverter is stopped. By stopping the inverter when the switching power supply voltage falls to this predetermined value or higher, the system preliminarily ensures safe deceleration while preventing breakdown, avoiding both harmful outcomes.
3Adaptability or versatility
If the switching power supply voltage falls below minimum required voltage, then connection switching device cannot operate, but arc discharge occurs causing contact welding and breakdown
Solution Approach 1:
The control device monitors the switching power supply voltage and uses this feedback to determine when to stop the inverter. By continuously detecting the voltage level and comparing it with the predetermined threshold, the system automatically stops the inverter at the appropriate moment, preventing the voltage from falling to levels that would cause arc discharge while maintaining operational capability.
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
The solution effectively prevents breakdowns of the connection switching device, extends the lifetime of the motor driving apparatus, and allows for the use of less expensive components, reducing costs while enhancing reliability.
Implementation Method 1
a capacitor configured to store an electric charge to output a DC voltage
Implementation Method 2
The electromagnetic switches return to a certain connection state when the power supply is lost
Implementation Method 3
If the electromagnetic switches are switched before the inverter for driving the motor is stopped, arc discharge may occur between the contacts, which may result in contact welding, and breakdown
Data Source
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AI summary
An electric quantity of a power supply of a connection switching device (60) for switching the connection state of a motor (7), or at least one electric quantity which varies with the first-mentioned electric quantity is detected (90), the result of the detection is used to detect or predict a fall of a voltage of the switching power supply. Based on the result of the detection or prediction, an inverter is so controlled as to stop the motor before the voltage (V60) of the switching power supply falls below the minimum voltage required for the operation of the connection switching device. Breakdown of the connection switching device can be prevented.