Pulse Shift Protection for Phase-to-Phase Short Circuit Detection
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Solution Overview
Problem
Existing electric motor drive systems face challenges in detecting phase-to-phase short circuits without causing significant disturbance to the output voltage, which can affect motor performance and produce unwanted noise.
Innovation Solution
A pulse shift protection method that calculates the optimal time for short circuit detection online, executing it when the output voltage is far from active vectors to minimize disturbance, using a combination of look-up tables, timers, and target angles to determine execution instances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the short circuit detection function is executed periodically to detect phase-to-phase short circuits, then the reliability of short circuit detection is improved, but the output voltage disturbance increases and motor performance deteriorates
Solution Approach 1:
The short circuit detection function is executed periodically at optimized intervals rather than continuously, balancing detection reliability with minimal output voltage disturbance. The periodic execution is timed to occur at specific moments in the PWM cycle when disturbance is minimized.
Solution Approach 2:
The optimal execution instant for the short circuit detection function is pre-calculated and stored in a lookup table based on PWM duty cycles and motor frequencies. This preliminary calculation allows the system to execute detection at predetermined optimal moments without real-time computation delays.
2Reliability
If the short circuit detection function is executed frequently to improve detection speed, then the reliability of short circuit detection is improved, but the current waveform quality deteriorates and acoustic noise increases
Solution Approach 1:
The detection function executes periodically at optimized intervals rather than continuously, reducing the frequency of executions to minimize acoustic noise while maintaining adequate detection speed for safety-critical applications.
Solution Approach 2:
The system uses its own operational parameters (PWM duty cycle, motor frequency) to determine the optimal detection timing, making the detection schedule adaptive to current operating conditions without external intervention.
3Device complexity
If the short circuit detection function is executed at any instant to simplify control, then the device complexity is reduced, but the output voltage disturbance increases
Solution Approach 1:
The complex task of determining optimal detection instants is performed in advance and stored in a lookup table. During operation, the system simply queries the table with current PWM duty cycle and frequency parameters, avoiding real-time complex calculations while achieving optimal disturbance minimization.
Solution Approach 2:
A lookup table serves as an intermediary between the simple query (current operating parameters) and the complex optimal detection timing. This intermediary pre-computes and stores the relationship, allowing fast retrieval without complex real-time computation.
Data Source
AI summary
The present invention is directed at a pulse shift protection method for detecting a phase-to-phase short circuit in a drive for controlling electric motors, wherein the drive provides an output voltage to the electric motor, and wherein the instant, at which a short circuit detection function is executed, is chosen to minimize disturbance in the output voltage of the drive. The invention is also directed at a drive for controlling electric motors, said drive including a controlling portion for generating an output signal and an output portion connectable to an electric motor. The drive is provided for executing the above-mentioned pulse shift protection method.