Motor Drive Safe-State Control with Phase Voltage Ramp-Down
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Solution Overview
Problem
Existing electric motor drive systems face challenges in safely transitioning to a safe state without causing high current transients that can damage the inverter or trigger overcurrent protection, particularly when using Active Short Circuit (ASC) due to the high current transient generated during the transition.
Innovation Solution
A computer system that controls the electric motor drive system by ramping down the initial phase voltage of the electrical machine before short-circuiting it through the inverter, using previously determined machine parameters and assuming a constant speed to reduce the voltage gradually, thereby minimizing high current transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Active Short Circuit (ASC) is used for safe state operation, then the safety level is improved, but high current transients are generated that can damage the inverter or trigger overcurrent protection
Solution Approach 1:
The patent applies preliminary action by ramping down the phase voltage to zero before triggering the Active Short Circuit safe state. This preparatory voltage reduction prevents harmful current transients from damaging the inverter when the short circuit is activated, while still achieving the desired safe state operation.
2Speed
If phase voltage is rapidly reduced to zero, then the response time is improved, but high current transients are generated that can damage the inverter
Solution Approach 1:
The patent applies preliminary anti-action by implementing a controlled voltage ramp-down process before the safe state transition. This gradual voltage reduction counteracts the potential for harmful current transients, protecting the inverter while still achieving timely safe state operation.
Data Source
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AI summary
A computer system is provided. The computer system comprises processing circuitry configured to: obtain a safe state request for an electric motor drive system (11) comprising an inverter (13) and an electrical machine (10) having a plurality of phases; determine, from a plurality of electrical machine parameters obtained prior to obtaining the safe state request, at least one initial phase voltage for the electrical machine (10); ramp down the magnitude from the at least one initial phase voltage while controlling the electrical machine (10); and short-circuit the electrical machine (10) through the inverter (13) when the at least one initial phase voltage has been ramped down.