Motor Control Apparatus Reducing Leakage Current via Phase Windings
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Solution Overview
Problem
Existing motor control apparatuses experience high frequency leakage currents due to voltage variations in motor frame, leading to electromagnetic interference and increased copper and iron losses, despite attempts to suppress these currents through PWM control and voltage averaging.
Innovation Solution
The motor control apparatus divides phase windings into sets and employs a PWM control method where switching sequences alternate the connection of phase winding ends to the positive and negative power supply sides, synchronizing the phase relationship between sets to minimize current ripples and frame voltage variations, thereby reducing high frequency leakage currents without using common mode coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If PWM control is used to suppress voltage variation and high frequency leakage current, then electromagnetic interference is reduced, but current ripples increase and copper losses increase
Solution Approach 1:
The phase windings are divided into two sets (first set and second set). The PWM control means for the first set and the PWM control means for the second set operate with different switching sequences that are phase-shifted relative to each other. This segmentation allows the voltage variations from one set to compensate for the other, reducing overall current ripples while maintaining suppression of high frequency leakage current.
2Object-affected harmful factors
If voltage averaging is used to suppress high frequency leakage current, then electromagnetic interference is reduced, but the complexity of the control system increases
Solution Approach 1:
The invention employs periodic switching sequences with specific phase relationships. The PWM control means for the first set of phase windings and the PWM control means for the second set execute switching sequences that are phase-shifted by a predetermined angle. This periodic, synchronized action naturally averages the voltage variations over time, suppressing high frequency leakage current without requiring additional complex control circuitry.
3Productivity
If switching elements are used for high frequency PWM control, then motor control efficiency is improved, but voltage variation at switching causes high frequency leakage current
Solution Approach 1:
The invention introduces an intermediary phase relationship between two sets of phase windings. By controlling the switching sequences of the first and second sets with a predetermined phase shift, the voltage variations generated by high frequency switching in one set act as a mediator to cancel out the harmful effects of the other set, thereby maintaining high motor control efficiency while suppressing high frequency leakage current.
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 effectively reduces current ripples and frame voltage variations, minimizing electromagnetic interference and associated losses, while preventing high frequency leakage currents, thus enhancing motor control efficiency.
Implementation Method 1
PWM control means for PWM-controlling the respective inverter type drive means
Implementation Method 2
a phenomenon such that a high frequency leakage current flows into a grounding conductor through stray capacitance of the motor windings
Data Source
AI summary
The present invention restrains high frequency leakage current while reducing ripples of current flowing through a motor having one set and another set of independent phase windings. A plurality of inverter type drive means drives the respective phase windings and a PWM control means controls the respective inverter type drive means, by a switching sequence connecting one end of all phase windings including the other set to the negative side of the power supply when both ends of the phase winding included in one set are connected to the positive side of the power supply and connecting at least one end of all phase windings included in the other set to the positive side of the power supply when both ends of at least one phase winding included in one set are connected to the negative side of the power supply.