Multi-Phase Machine Switch-On Using Vector Matching
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Solution Overview
Problem
Switching on multi-phase electrical machines in motor vehicles, especially at high speeds, often results in overshooting phase currents and high electrical and mechanical loads due to interactions between phase and pole wheel voltages, making it difficult to manage the switching process effectively.
Innovation Solution
The method involves applying a phase voltage with a phase voltage vector in PWM operation that matches the rotor voltage vector when the excitation current is ramped up, switching to block operation when the magnet wheel voltage vector reaches a specific threshold, optimizing the switching time to avoid current peaks and ensuring smooth operation regardless of vehicle speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phase voltage is switched on first, then the electrical machine can start operating, but phase current may overshoot causing high electrical and mechanical loads
Solution Approach 1:
The patent applies preliminary action by first switching on the excitation voltage to build up the magnetic field before applying the phase voltage. This preparatory step ensures that when the phase voltage is applied, the rotor already has the necessary magnetic field to prevent current overshoot. The excitation current is ramped up in advance during PWM operation, creating the magnetic field conditions needed for smooth subsequent phase voltage application.
Solution Approach 2:
The patent employs dynamics by using PWM (Pulse Width Modulation) operation to dynamically control the excitation current ramp-up process. The PWM technique allows the excitation voltage to be applied in a controlled, time-varying manner rather than a simple step function, enabling smooth buildup of the magnetic field. The transition from PWM operation to block operation is dynamically timed based on when the magnet wheel voltage vector reaches the phase voltage vector, optimizing the switching moment to prevent current peaks.
2Reliability
If excitation voltage is switched on first, then the magnetic field is established, but pole wheel voltage interacts negatively with phase voltage causing high loads
Solution Approach 1:
The patent applies feedback by continuously monitoring the magnet wheel voltage vector and using this information to determine the optimal switching moment. The control system evaluates when the magnet wheel voltage vector reaches the phase voltage vector in terms of both magnitude and direction, and only then transitions from PWM to block operation. This feedback mechanism ensures that the phase voltage is applied at the precise moment when pole wheel voltage interaction is minimized, preventing harmful effects.
Solution Approach 2:
The patent employs parameter changes by transitioning the electrical machine through different operational states with changing parameters. The system starts in PWM operation mode with ramping excitation current, then transitions to block operation mode when specific voltage vector conditions are met. This parameter change approach allows the magnetic field to be established progressively while controlling the timing of phase voltage application to avoid negative interactions.
3Object-affected harmful factors
If switching on is delayed until speed reduces, then current peaks are avoided, but switching responsiveness is reduced
Solution Approach 1:
The patent applies preliminary action by establishing the magnetic field through excitation voltage application before the harmful high-speed conditions occur. By ramping up the excitation current during PWM operation, the system prepares the magnetic field in advance, enabling immediate phase voltage application without waiting for speed reduction. This preliminary magnetic field establishment eliminates the need to delay switching for current peak avoidance.
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 approach allows for optimal switching times, minimizing undesired current peaks and loads, enabling the electrical machine to be switched on gently and efficiently as a motor or generator, supporting the internal combustion engine without waiting for reduced speeds, and is suitable for various vehicle types, including hybrid vehicles.
Implementation Method 1
If an excitation voltage is switched on first, a pole wheel voltage with a pole wheel voltage vector is first induced in the stator
Implementation Method 2
The electrical machine is switched on in a PWM operation with a phase voltage being applied to the stator winding, which corresponds in terms of magnitude and direction to a rotor voltage vector
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method for switching on a multi-phase electrical machine (110) in a motor vehicle. Said multi-phase electrical machine (110) comprises a rotor with a rotor winding (101) and a stator with a multi-phase stator winding. In a PWM mode, a phase voltage with a phase voltage vector is applied to the stator winding, said vector corresponding to the vector of a pole wheel voltage in terms of amount and direction, and the rotor winding (101) is energized with an excitation current, and the PWM mode is deactivated and a burst mode is activated to apply the phase voltage when at least one parameter influencing the pole wheel voltage reaches a threshold value.