Motor Control Apparatus Power Failure Detection
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Solution Overview
Problem
Motor control apparatuses face challenges in efficiently performing protection operations during power failures on the three-phase AC input side, leading to potential equipment damage and economic losses due to inappropriate execution of protection operations during instantaneous or successive power failures.
Innovation Solution
The motor control apparatus includes a rectifier, inverter, AC voltage detection unit, voltage amplitude calculation unit, power failure recovery detection unit, protection operation command unit, time measurement unit, and condition change unit, which dynamically adjust power failure detection reference voltage and protection operation timing based on elapsed time to enhance detection sensitivity and minimize energy storage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection operation is executed immediately upon detecting power failure, then equipment damage is prevented, but manufacturing line stops causing economic loss during instantaneous power failures
Solution Approach 1:
The power failure detection reference voltage is dynamically changed based on elapsed time. Initially set to a first value for normal operation, it switches to a second value (higher than first but lower than recovery reference) after a predetermined time elapsed since recovery. This dynamic adjustment enables the system to tolerate instantaneous power failures while protecting against successive failures, resolving the contradiction between equipment protection and manufacturing continuity.
2Productivity
If power failure detection reference voltage is set high, then instantaneous power failures are tolerated, but successive power failures may not be detected in time
Solution Approach 1:
The system periodically switches the detection reference voltage between two levels based on elapsed time since power recovery. During the first period (0 to predetermined time), the reference voltage is at the first level allowing instantaneous failures. After the predetermined time, it switches to the second level for detecting successive failures. This periodic switching resolves the contradiction by adapting the detection threshold to the current operational state.
3Reliability
If protection operation reference time is short, then protection is provided quickly, but energy storage units must be large to maintain operation
Solution Approach 1:
The protection operation reference time is set to a relatively long duration, allowing the energy storage unit to be smaller. The system accepts that protection operation takes longer to execute, trading off protection speed for reduced energy storage requirements. This resolves the contradiction by choosing partial protection action (longer reference time) to minimize energy storage capacity.
Data Source
AI summary
A motor control apparatus includes a rectifier which converts AC of a power source to DC, an inverter which converts DC to AC for a motor, a voltage amplitude calculation unit which calculates a power source voltage amplitude value, a power failure recovery detection unit which determines whether or not the AC input side has transitioned to a power failure state or a power recovery state on the basis of the power source voltage amplitude value, a protection operation command unit which outputs a protection operation command when a reference time has elapsed from a time point at which the AC input side transitioned to the power failure state, a time measurement unit which measures an elapsed time from when the AC input side transitioned to the power recovery state, and a condition change unit which changes the power failure reference voltage value and/or the reference time.