Motor Vehicle Control Unit Discharge via Frequency Reduction
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Solution Overview
Problem
In electric vehicles, high-voltage intermediate circuits pose a safety risk during accidents or maintenance, as existing solutions require additional components like ohmic resistors for discharging, which are not always efficient or safe.
Innovation Solution
A control unit with an inverter and transformer that reduces the operating frequency to quickly discharge the intermediate circuit capacitor, disconnecting the high-voltage battery and connecting the remaining energy to a low-voltage network, thereby reducing the risk of electric shock without additional resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional ohmic resistors are used to discharge the intermediate circuit capacitor, then the discharge function is provided, but the device complexity increases and space is required for additional components
Solution Approach 1:
The inverter is designed to perform both its primary function of driving the electrical machine and an additional function of discharging the intermediate circuit capacitor. By utilizing the existing inverter switches and transformer, the system achieves discharge capability without requiring separate dedicated discharge resistors or switching elements, thereby reducing device complexity while maintaining the discharge function.
2Speed
If the inverter operating frequency is reduced during discharge, then the AC resistance of the transformer decreases and discharge speed increases, but the power conversion efficiency may be affected
Solution Approach 1:
The inverter operating frequency is dynamically adjusted based on the discharge requirement. During normal operation, the inverter operates at its standard frequency for optimal power conversion efficiency. When discharge is required, the frequency is temporarily reduced to decrease the transformer's AC resistance and increase discharge speed. This dynamic frequency adjustment allows the system to optimize for discharge performance when needed while maintaining efficient power conversion during normal operation.
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 efficiently discharges the intermediate circuit to a safe voltage, reducing the risk of electric shock during accidents or maintenance, and prevents overheating of the transformer and inverter by limiting current based on magnetic flux and temperature.
Implementation Method 1
a control unit with an inverter and transformer that reduces the operating frequency to quickly discharge the intermediate circuit capacitor
Implementation Method 2
A control unit with an inverter and transformer that reduces the operating frequency to quickly discharge the intermediate circuit capacitor
Data Source
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AI summary
The invention relates to a control unit for a motor vehicle. Said control unit comprises a voltage converter which has an inlet for a direct voltage network. Said voltage converter is designed to generate a direct voltage smaller than an input voltage on the inlet for the direct voltage network and the direct voltage is emitted on the outlet side. According to the invention, the voltage converter comprises an inverter and a transformer which is connected to said inverter. Said voltage converter also comprises an inlet for a discharge signal and is designed to discharge by means of the inverter an intermediate circuit capacitor which is connected to the inlet of the direct voltage network in accordance with the discharge signal, and to reduce a working frequency of the inverter, in particular, compared to the frequency with no discharge signal.