Current Pulse Limit Protection for Motor Controllers
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Solution Overview
Problem
Power tools, such as motorized ratchet wrenches, can experience intermittent current pulses during normal operation, which are not detected by existing protection systems, leading to potential damage to the motor controller and battery due to their short duration.
Innovation Solution
Implementing a current pulse limit protection system in the tool's controller, which measures and counts current pulses exceeding specific thresholds, and ceases operation when a predetermined number of pulses is reached, in conjunction with current limit protection to address extended overcurrent events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the controller uses traditional overcurrent detection methods, then it can detect sustained overcurrent events, but it cannot detect short-duration current pulses that occur during normal operation
Solution Approach 1:
The controller dynamically adjusts its detection behavior based on the characteristics of detected current pulses. When a current pulse exceeds the first threshold, the controller enters a pulse-counting mode with a predetermined time window, transitioning from static threshold detection to dynamic pulse monitoring. This allows the system to adaptively respond to different operating conditions without requiring completely separate detection circuits.
Solution Approach 2:
The overcurrent protection function is segmented into two distinct detection modes: traditional sustained overcurrent detection and new short-pulse overcurrent detection. The controller divides the detection time into intervals and applies different detection logic to each segment, allowing it to handle both long-duration and short-duration overcurrent events with the same hardware infrastructure.
2Reliability
If the controller ceases operation immediately upon detecting any overcurrent pulse, then it protects the controller and battery from damage, but it reduces productivity by stopping operation during normal high-current events
Solution Approach 1:
The controller employs periodic pulse counting within predetermined time windows rather than immediate cessation upon single pulse detection. It monitors the frequency and accumulation of current pulses over time, only ceasing operation when the pulse count exceeds the threshold within the monitoring period. This periodic assessment allows normal high-current operations to continue while still protecting against damaging repetitive pulse patterns.
Solution Approach 2:
The controller implements feedback by continuously monitoring current pulse occurrences and adjusting its operational state based on the accumulated pulse count. The system provides feedback to the operation logic, allowing it to distinguish between acceptable high-current events and dangerous repetitive pulsing, thereby maintaining productivity while ensuring protection.
3Measurement precision
If the controller monitors current continuously with high precision, then it can detect all overcurrent events including short pulses, but it increases energy consumption and processing load
Solution Approach 1:
The controller changes detection parameters dynamically based on operating conditions. It uses a first threshold for normal pulse detection and a second, higher threshold for immediate protection activation. The controller also adjusts the monitoring intensity based on whether pulses are being detected, reducing continuous high-precision monitoring to event-triggered measurement, thereby lowering average energy consumption while maintaining detection precision when needed.
Data Source
AI summary
The present invention relates to current pulse limiting protection of a motorized device that includes a motor, a controller, and a power source (such as a battery). The controller implements current pulse limit protection to protect the controller and battery from damage due to overcurrent pulse events. For example, the controller may measure current flowing through the controller, and detect a number of current pulses that meets or crosses a first current threshold, regardless of a duration of each of the current pulses. The controller counts each current pulse that meets or crosses the first current threshold, and if the number of current pulses counted meets or exceeds a threshold number of pulses, the controller indicates a fault and ceases operation of the tool to protect the controller and battery from damage.