Back-up Power Control System with VFD and Bypass Starter

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Solution Overview

Problem

Existing back-up power systems for AC-powered components during power outages are costly and inefficient, requiring separate DC motors and active power electronics that generate significant heat, increasing air conditioning needs and overall costs.

Innovation Solution

A back-up power control system that includes a variable frequency drive (VFD) coupled to a DC bus and a bypass starter connected to an AC bus, with a controller that switches the VFD between active and low-power modes based on power availability, allowing the system to convert DC power to selectable frequency AC power only during outages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If active power electronics are used in UPS systems to route conditioned AC line voltage to components during normal operation and switch to DC battery power during outages, then back-up power reliability is improved, but heat generation increases significantly and air conditioning capability must be increased

Engineering Contradiction:

Improveback-up power reliabilityVSAvoidheat generation

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent extracts the active power electronics from the normal operation path, using them only during outage conditions. The bypass starter handles normal AC power routing without active electronics, while the VFD with DC batteries provides back-up power only when needed, eliminating continuous heat generation while maintaining reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The system switches between two operational modes: normal AC power mode using the bypass starter, and back-up DC power mode using the VFD and batteries during outages. This periodic activation of active power electronics only when needed reduces continuous heat generation while ensuring reliability during critical periods.

Inventive Principle:

Principle #19Periodic action

2Reliability

If separate DC back-up motors are included for each AC-powered component to replace the AC motor during power outages, then back-up power reliability is improved, but initial cost, maintenance cost, and system footprint increase

Engineering Contradiction:

Improveback-up power reliabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses a single VFD system that can universally replace multiple AC motors during outages. Instead of having dedicated DC motors for each AC component, the VFD converts DC battery power to AC power signals that can drive any AC-powered component, reducing system complexity while maintaining reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent replaces the mechanical approach of using separate DC motors with a电气 substitution approach. The VFD uses power electronics to convert DC to AC, eliminating the need for mechanical DC motors and their associated complexity while providing the same back-up function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If inverter-ready motors and cables are used for critical components instead of general duty AC motors and power cables, then back-up power compatibility is improved, but initial cost increases

Engineering Contradiction:

Improveback-up power compatibilityVSAvoidinitial cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent makes the motor configuration dynamic by using the VFD to generate adjustable frequency AC power. The VFD can adapt its output to match the requirements of different motors, allowing general duty motors to be used during back-up operation without requiring expensive inverter-ready motors, thus reducing initial cost while maintaining compatibility.

Inventive Principle:

Principle #15Dynamics

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 solution reduces heat generation, decreases initial and maintenance costs, and allows the use of general duty motors and cables, while extending the availability of the DC power source by operating components at partial speeds during outages.

Implementation Method 1

a variable frequency drive (VFD) coupled to a DC bus... said VFD converts DC power provided by the DC bus into a selectable frequency AC power signal

Methodology Applied

Scientific EffectPower conversion (DC to AC):

Data Source

PatentUS10985608B2Back-up power system for a component and method of assembling same

Publication Date: 2021.04.20 GE INFRASTRUCTURE TECH LLC

AI summary

A back-up power control system for an AC-powered component includes a bypass starter coupled to an AC bus, and a variable frequency drive (VFD) coupled to a DC bus. The VFD is selectively operable in each of (i) an active mode, such that said VFD converts DC power provided by the DC bus into a selectable frequency AC power signal, and (ii) a stand-by low-power mode. The system also includes a controller operatively coupled to the bypass starter and the VFD and programmed to (a) while the AC bus is in a normal operating condition, command the VFD to the low-power mode and operatively couple the bypass starter to the AC-powered component, and (b) while the AC bus is in an outage condition, command the VFD to the active mode and operatively couple the VFD to the AC-powered component.