Electric Drive System Neutral Point Charging Circuit
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Solution Overview
Problem
Existing charging systems for energy stores in electric vehicles are not cost-effective and lack efficient voltage management, leading to potential overcharging and premature aging of energy storage devices.
Innovation Solution
A drive system comprising a three-phase electric motor with an inverter and energy store, where the electric motor is fed by an inverter supplied from the energy store, allowing current to be supplied to the neutral point from a rectifier with a secondary winding inductively coupled to a primary winding, enabling efficient voltage level adjustment and protection against overcharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a rectifier is fed from a secondary winding with voltage far lower than charging voltage, then a compact charging circuit is achieved, but voltage level adjustment becomes necessary
Solution Approach 1:
The inverter's stator windings are utilized for multiple purposes: driving the electric motor and simultaneously functioning as inductors in the charging circuit. This multi-functionality eliminates the need for separate charging inductors, reducing component count and circuit complexity while enabling voltage level adjustment from low secondary voltage to high charging voltage
Solution Approach 2:
The system uses its own existing components (inverter and stator windings) to perform the voltage boosting function required for charging. The inverter, already present for motor control, is made to serve the additional function of voltage conversion, making the charging circuit self-sufficient without requiring external voltage conversion equipment
2Loss of energy
If direct charging from secondary winding is used when voltage is above first critical value, then charging efficiency is improved, but risk of overcharging and energy store damage increases
Solution Approach 1:
The control unit continuously monitors the voltage at the neutral point and compares it against critical values. Based on this feedback, the control unit dynamically switches between charging modes (direct charging or inverter-mediated charging) and activates protection mechanisms, ensuring both efficiency and safety by adapting to real-time voltage conditions
Solution Approach 2:
The system proactively prevents overcharging by implementing multiple protective measures: diverting current through the inverter when voltage exceeds the first critical value, and providing passive protection through the second current path when voltage exceeds the second critical value. These preliminary actions prevent harmful effects before they occur
3Reliability
If passive protection current path is released for voltage above second critical value, then reliability is improved, but device complexity increases
Solution Approach 1:
The passive protection current path is pre-configured in the circuit but remains inactive during normal operation. When voltage exceeds the second critical value, this pre-prepared path automatically activates to divert current and protect the energy store. This preliminary preparation ensures immediate protection without requiring complex real-time decision-making or additional active components
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 allows for a compact, wide-voltage charging circuit that protects the energy store from overcharging and premature aging, maintaining efficiency even with fluctuating voltages and varying supply networks, while reducing losses and ensuring reliable energy transmission.
Implementation Method 1
a secondary winding, with the secondary winding being supplied from a primary winding which is provided inductively coupled to the secondary winding
Data Source
Figure 1
AI summary
The invention relates to drive system and to a method for operating the drive system, comprising an electric motor, inverter, energy accumulator, wherein the electric motor can be fed from the inverter, which can be supplied from the energy accumulator. At least one stator winding of the electric motor can be supplied with a current which can be controlled by a switch and is supplied from an electric energy source that is different from the energy accumulator.