Phase Angle Shift for Cycle-Skipping Harmonic Reduction

Solution Overview

Problem

Cycle-skipping motor speed control systems experience high-amplitude harmonic components when multiple cycle skippers are connected to a common source with temporally aligned firing patterns, leading to undesirable effects like vibration and noise.

Innovation Solution

Implementing a phase angle shift in the firing patterns of multiple cycle skippers connected to a common source to distribute current flow more evenly, reducing harmonic components by ensuring non-concurrent firings across the firing cycle.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple cycle skippers are connected to a common source with temporally aligned firing patterns, then the system can drive multiple loads efficiently, but high-amplitude harmonic components are generated causing vibration and noise

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies periodic action by implementing phase angle shifting in the firing patterns of multiple cycle skippers. Each cycle skipper operates periodically but with different phase angles (e.g., 0°, 120°, 240°), which distributes the current flow more evenly over time and reduces the amplitude of harmonic components while maintaining system productivity

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the parameter of firing angle timing for each cycle skipper. By adjusting the phase angle of each cycle skipper's firing pattern relative to the common source voltage, the system transforms the temporal distribution of current flow, thereby reducing harmonic distortion without sacrificing efficiency

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If firing patterns are temporally aligned for simplicity of control, then the control system is easier to operate, but harmonic components increase causing undesirable effects

Engineering Contradiction:

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The patent introduces dynamic phase angle shifting where the firing patterns of multiple cycle skippers are intentionally staggered in time. This dynamic temporal distribution of firing events simplifies control by using standardized cycle-skipping logic while eliminating the need for complex synchronization, and simultaneously reduces harmonics by avoiding concurrent firings

Inventive Principle:

Principle #15Dynamics

3Power

If cycle skippers fire concurrently to maximize power delivery, then the power output is maximized, but the magnitude of harmonic components increases

Engineering Contradiction:

Core Design Contradiction:

PowerVSObject-generated harmful factors

Solution Approach 1:

The patent segments the firing events of multiple cycle skippers by applying different phase angles to each. Instead of all cycle skippers firing concurrently at the same instant, they are divided into staggered firing groups, which maintains overall power delivery while distributing the harmonic energy across different time intervals, thereby reducing peak harmonic amplitude

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS7508159B2Method for controlling a cycle-skipping control system including computer readable code and controller for performing such method

Publication Date: 2009.03.24

AI summary

A method, computer-readable code, and controller are provided for controlling a cycle-skipping control system having two or more cycle skippers connected to a common multi-phase AC (alternating current) power source to drive a variable frequency load. A respective firing sequence is generated to be applied to a plurality of power switches in the two or more cycle skippers for implementing a desired mode of operation. A phase angle shift is provided between each respective firing sequence to be applied to the two or more cycle skippers over a firing cycle. This enables a non-concurrent firing for each cycle skipper over the firing cycle.