Motor Current Control for Permanent Magnet Demagnetization Prevention
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Solution Overview
Problem
Existing methods for preventing demagnetization of permanent magnets in motors, such as using resistors or triacs, result in power loss and limited effectiveness, as they either consume unnecessary battery power or fail to manage excessive currents during normal operation.
Innovation Solution
A motor-driven appliance with a battery, motor, momentary maximum current upper limit storage, current detection, threshold setting, exceedance determination, and flow interruption units, which continuously monitor and interrupt the current path before it exceeds a predetermined threshold, preventing demagnetization while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is inserted in the current path to prevent demagnetization, then demagnetization is suppressed, but power loss due to resistance occurs continuously and battery remaining capacity decreases faster
Solution Approach 1:
The invention uses periodic action by inserting the resistor only during the activation period when rush current occurs, rather than continuously. The control unit activates the resistor during activation and deactivates it during normal operation, thereby suppressing demagnetization when needed while avoiding continuous power loss.
2Reliability
If a triac is used to control current at activation, then rush current is prevented, but excessively large current during normal operation cannot be dealt with
Solution Approach 1:
The invention applies dynamics by making the control method adaptable to different operational states. The control unit dynamically switches between activation-mode control (using triac) and normal-operation control (using resistor insertion), allowing the system to handle both rush current at activation and excessively large current during normal operation appropriately.
3Reliability
If the current threshold is set low to prevent demagnetization, then demagnetization is suppressed, but normal operation may be interrupted unnecessarily
Solution Approach 1:
The invention uses local quality by setting different current thresholds for different operational phases. A first threshold is set for activation period to handle rush current, and a second (higher) threshold is set for normal operation to allow legitimate high current while still preventing demagnetization. This localized threshold setting prevents unnecessary interruptions during normal operation.
4Reliability
If the resistor is activated continuously to ensure demagnetization suppression, then demagnetization is reliably prevented, but battery power is unnecessarily consumed
Solution Approach 1:
The control unit activates the resistor periodically based on operational phase detection. During activation period, the resistor is activated to suppress demagnetization. During normal operation, the resistor is deactivated to avoid unnecessary power consumption. This periodic activation strategy maintains reliability while minimizing energy use.
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
Effectively suppresses demagnetization of permanent magnets throughout the motor's operation period while reducing unnecessary battery power consumption by promptly interrupting excessive currents, thus enhancing the motor's performance and battery life.
Implementation Method 1
a current detection unit that detects a current flowing in the motor
Implementation Method 2
demagnetization of the permanent magnets is caused under the influence of a magnetic field generated from the armature
Implementation Method 3
demagnetization of the permanent magnets in the motor causes a change in characteristics of the motor
Data Source
AI summary
A motor-driven appliance includes a battery; a motor including permanent magnets as field magnets; a momentary maximum current upper limit storage unit in which a predetermined momentary maximum current upper limit is stored; a current detection unit that detects a current flowing in the motor; a current threshold setting unit that generates a current threshold based on the momentary maximum current upper limit, and outputs the generated current threshold; a current exceedance determination unit that determines whether the current detected by the current detection unit has become equal to or greater than the current threshold, and outputs an interruption signal used to interrupt a current path from the battery to the motor when the detected current has become equal to or greater than the current threshold; and a current flow interruption unit that interrupts the current path when the interruption signal is outputted from the current exceedance determination unit.