Synchronizing Current and Rotor Angle Sensors for Three-Phase Motor Control
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Solution Overview
Problem
Current current control apparatuses for three-phase rotary machines face accuracy issues in transforming actual phase currents into two-phase currents in a rotating coordinate system due to asynchronous measurement timing between current sensors and rotational angle sensors.
Innovation Solution
A current control apparatus that includes a synchronizing unit to synchronize the measurement timing of phase currents with the rotational angle, a current calculator to calculate two-phase currents based on these synchronized signals, and a transmitter to communicate these values for precise control of three-phase currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If asynchronous measurement timing is used between current sensors and rotational angle sensor, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing transformation coefficients in a lookup table before actual current transformation. The transformation coefficients are computed based on rotor position at predetermined intervals, and these pre-computed coefficients are then used for real-time current transformation, eliminating the need for complex real-time synchronization while maintaining high measurement precision.
Solution Approach 2:
The patent introduces transformation coefficients as an intermediary element between the rotational angle sensor and the current transformation process. These coefficients act as a mediator that decouples the timing requirements, allowing current transformation to use pre-computed coefficients rather than requiring simultaneous measurement of current and rotor position, thus resolving the synchronization issue without adding complexity.
2Measurement precision
If real-time synchronization is implemented between current sensors and rotational angle sensor, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Instead of implementing complex real-time synchronization, the patent uses preliminary action by pre-computing transformation coefficients at predetermined intervals and storing them in a lookup table. This approach achieves high measurement precision without requiring complex real-time synchronization mechanisms, as the pre-computed coefficients are simply looked up during current transformation.
Solution Approach 2:
The patent uses a cost-effective approach by employing a lookup table with pre-computed transformation coefficients rather than implementing expensive and complex real-time synchronization hardware or software. The lookup table provides sufficient accuracy for the application while being computationally inexpensive and easy to implement.
Data Source
AI summary
In an apparatus, a synchronizing unit synchronizes a measurement timing of values of first and second phase currents by a current sensor with a measurement timing of a rotational angle of a rotor by a rotational angle sensor. A current calculator calculates, based on the first and second parameter signals and the rotational angle of the rotor, values of two phase currents in a rotational coordinate system defined with respect to the rotor. A transmitter transmits the values of the two phase currents using a communication protocol. A controller communicates with the transmitter using the communication protocol to receive the values of the two phase currents. The controller controls the first phase current, the second phase current, and a third phase current flowing through respective first, second, and third phase windings of a three-phase rotary machine according to the values of the two-phase currents.