Field Current Control for Rotary Electric Machine Efficiency
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Solution Overview
Problem
Existing control techniques for field-winding-type rotary electric machines, such as ISGs, face challenges in improving power efficiency due to complex control of stator and field currents, leading to increased copper and iron losses, especially at varying rotational speeds.
Innovation Solution
A control unit is implemented that adjusts the field current to minimize the difference between induced and applied voltages, thereby reducing the phase current through the armature winding, simplifying control and minimizing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If stator current and field current are simultaneously controlled to ensure generated power at varying rotational speeds, then power generation capability is maintained, but control complexity increases and power efficiency deteriorates due to increased copper and iron losses
Solution Approach 1:
The patent segments the control into two independent parts: (1) stator current control to maintain generated power, and (2) field current control to minimize iron losses. This segmentation allows each control to be optimized independently, reducing overall control complexity while maintaining power generation capability.
Solution Approach 2:
The patent dynamically adjusts field current based on rotational speed to minimize iron losses. At low speeds, field current is increased to ensure generated power; at high speeds, field current is decreased to reduce iron losses. This dynamic adjustment optimizes power efficiency across the operating range.
2Power
If stator current is increased to ensure generated power at high rotational speeds, then power generation capability is maintained, but copper losses increase reducing power efficiency
Solution Approach 1:
The patent changes the field current parameter dynamically based on rotational speed. At high speeds, field current is reduced to decrease magnetic flux, which allows generated power to be maintained with lower stator current, thereby reducing copper losses in the stator windings.
3Power
If field current is increased to ensure generated power at low rotational speeds, then power generation capability is maintained, but iron losses increase reducing power efficiency
Solution Approach 1:
The patent implements dynamic field current control where field current is adjusted according to rotational speed. At low speeds, field current is increased to ensure sufficient generated power; at high speeds, field current is decreased to minimize iron losses in the field winding and magnetic core.
4Measurement precision
If map data with multiple input values (output torque, rotational speed) and output values (stator current, field current) is used for control, then control accuracy is improved, but storage capacity requirements increase and control complexity increases
Solution Approach 1:
The patent segments the control strategy into two independent control loops: stator current control and field current control. This eliminates the need for complex multi-dimensional map data, reducing storage requirements and control complexity while maintaining adequate control accuracy for each variable.
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 enhances power efficiency by reducing copper losses and simplifying control, while maintaining optimal output torque and power generation across different rotational speeds.
Implementation Method 1
an induced voltage generated in the armature winding by rotation of the rotor
Data Source
AI summary
A control unit applied to a motor that includes a rotor having a field winding and a rotor having armature winding groups to control a field current passed through the field winding. Each of the armature winding groups is applied with a prescribed voltage. The field current is controlled so as to be a minimum field current value If_min with which a deviation between an amplitude of an induced voltage generated in the armature winding groups by rotation of the rotor, and an amplitude of the voltage applied to the armature winding groups becomes equal to or smaller than a prescribed value.