Rotary Machine Open Phase Detection via Current Sum Compensation
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Solution Overview
Problem
The existing rotary machine control devices are unable to perform open phase determination with high accuracy when the rotary machine is rotating due to the influence of motional electromotive force on the DC bus current.
Innovation Solution
A rotary machine control device that includes a voltage application unit, a current detection unit, and an open phase determination unit, which applies voltage between pairs of phases and compares the sum of currents flowing between these phases with a reference value to determine if an open phase has occurred, effectively canceling the effect of motional electromotive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rotary machine control device measures DC bus current to perform open phase determination, then the determination can be implemented, but the accuracy deteriorates when the rotary machine rotates due to motional electromotive force interference
Solution Approach 1:
The patent extracts and eliminates the harmful motional electromotive force component from the DC bus current measurement by applying a compensation voltage equal in magnitude but opposite in polarity to the motional electromotive force, thereby isolating the current component caused solely by the applied test voltage for accurate open phase determination
Solution Approach 2:
The patent changes the measurement approach by not directly measuring DC bus current, but instead measuring the current flowing through the rotary machine windings after compensating for motional electromotive force, transforming the measurement parameter from DC bus current to phase current with compensation
2Productivity
If the rotary machine rotates during operation, then the machine can perform work, but the open phase determination accuracy deteriorates due to motional electromotive force
Solution Approach 1:
The patent applies preliminary action by compensating for the motional electromotive force before performing the open phase determination measurement, ensuring that the measurement is performed under compensated conditions even while the machine is rotating and producing work
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
This approach allows for accurate open phase determination even when the rotary machine is rotating, preventing false determinations and ensuring reliable operation.
Implementation Method 1
the inverter applies a pulse-shaped voltage to each phase of the rotary machine one by one, and the magnitude of a direct current (DC) bus current of each phase that flows upon application of the pulse-shaped voltage is compared with a reference value
Implementation Method 2
detecting values of currents flowing between the respective pairs of the phases by monitoring the voltage command and the current information
Implementation Method 3
comparing a sum of the values of the currents flowing between the respective pairs of the phases with a predetermined reference value
Data Source
AI summary
A rotary machine control device includes a voltage application unit that applies a voltage to a rotary machine with three phases, a current detection unit that outputs current information representing information on a current caused to flow to the rotary machine by application of the voltage, a control unit that outputs a voltage command to apply a voltage between each of pairs of the phases of the rotary machine, and an open phase determination unit that performs open phase determination to determine whether an open phase occurs in the rotary machine, by detecting the values of currents flowing between the respective pairs of the phases by monitoring the voltage command and the current information, and by comparing the sum of the values of the currents flowing between the respective pairs of the phases with a predetermined reference value.