Motor Drive Overvoltage Alarm Level Setting
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Solution Overview
Problem
Motor drive devices face challenges in efficiently and reliably protecting elements from overvoltage in the DC link unit, as existing solutions either result in excessive margin settings or delayed crisis prevention, potentially leading to voltage exceeding the withstand voltage of components.
Innovation Solution
A motor drive device with a voltage detecting unit, alarm level setting unit, alarm determining unit, and alarm reporting unit that dynamically sets an overvoltage alarm level based on forecasting calculations of voltage increase, considering the time required for inverter stoppage, regenerated power conversion, and DC link capacitor capacitance, to prevent voltage from exceeding the withstand voltage of elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed overvoltage alarm level is set with excessive margin below withstand voltage, then element protection is ensured, but the alarm level becomes suboptimal and may cause unnecessary operations
Solution Approach 1:
The alarm level setting unit dynamically adjusts the overvoltage alarm level based on real-time parameters including inverter stoppage time, regenerated power conversion characteristics, and DC link capacitor capacitance. This transforms the fixed alarm level into a dynamic value that adapts to changing operating conditions, resolving the contradiction between ensuring protection and maintaining operation efficiency.
Solution Approach 2:
The system changes the alarm level parameter based on multiple factors: time required for inverter stoppage, amount of regenerated power, conversion capability of the converter, and capacitance of the DC link capacitor. By adjusting this parameter dynamically rather than using a fixed value, the system achieves both reliable protection and optimal operation efficiency.
2Productivity
If alarm level is set closer to withstand voltage to reduce margin, then operation efficiency improves, but voltage may exceed withstand voltage during alarm response time
Solution Approach 1:
The system performs preliminary calculation of the voltage increase that will occur during the inverter stoppage time before setting the alarm level. By anticipating the voltage rise during the response period, the alarm level is set at a value that prevents overvoltage even after the delay, allowing the alarm level to be optimally close to the withstand voltage without compromising protection.
Solution Approach 2:
The forecasting calculation unit predicts the voltage increase during alarm response time and the alarm level setting unit preemptively adjusts the alarm level to counteract this expected increase. This preliminary anti-action ensures that even with the response delay, the voltage will not exceed the withstand voltage, enabling higher alarm levels for improved efficiency.
3Device complexity
If conventional fixed alarm level method is used, then device complexity is low, but the alarm level cannot adapt to dynamic operating conditions
Solution Approach 1:
The system implements feedback by continuously monitoring operating parameters (inverter stoppage time, regenerated power amount, converter conversion capability, DC link capacitor capacitance) and using this information to dynamically adjust the alarm level. The forecasting calculating unit uses this feedback to predict voltage behavior and the alarm level setting unit adjusts accordingly, enabling adaptability while maintaining relatively simple control through automated calculations.
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 effectively sets an optimal overvoltage alarm level, preventing excessive margin and reliably protecting motor drive device elements from overvoltage, ensuring efficient operation and component safety.
Implementation Method 1
a DC link capacitor which is capable of accumulating DC power
Implementation Method 2
a converter which converts AC power supplied from an AC power supply side into DC power
Implementation Method 3
an inverter which converts the DC power supplied from a DC side into AC power for driving the motor
Data Source
AI summary
A motor drive device includes a converter which mutually converts power between AC power and DC power, an inverter which converts the DC power into AC power for driving a motor to output to a motor side, and converts regenerated AC power from the motor side into DC power to output to the DC side, a DC link unit which connects a DC side of the converter and a DC side of the inverter, a voltage detecting unit which detects a DC voltage value, an alarm level setting unit which sets an alarm level of the DC voltage value, an alarm determining unit which determines whether or not the DC voltage value exceeds the alarm level, and an alarm reporting unit which instructs the inverter to stop conversion operation when it is determined that the voltage value exceeds the alarm level.