AC-Powered VFD Control for Transport Refrigeration Compressors

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Solution Overview

Problem

Operating and maintaining a variable frequency drive (VFD) using DC power in trailer or container refrigeration units is complex and costly.

Innovation Solution

Implementing an AC-powered VFD system that converts 3-phase AC power into AC or DC power with adjustable attributes to drive the compressor and/or fans using AC power sources such as a diesel engine, generator, or electrical grid, optimizing power supply based on compressor and fan requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If DC power is used to operate VFD in transport refrigeration units, then the compressor can be controlled with variable speed, but the system complexity and maintenance cost increase

Engineering Contradiction:

Improvevariable speed controlVSAvoidsystem complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent changes the power source parameter from DC to AC, and modifies the VFD to accept AC input. This parameter change simplifies the overall system by eliminating DC-AC conversion components while maintaining variable speed control capability through AC-powered VFD technology.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If DC power is used to operate VFD in transport refrigeration units, then the compressor can be controlled with variable speed, but the maintenance cost increases

Engineering Contradiction:

Improvevariable speed controlVSAvoidmaintenance cost

Core Design Contradiction:

Adaptability or versatilityVSEase of repair

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

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

Provides a simple, efficient, and cost-effective solution for driving compressors and fans in transport refrigeration units, enabling wider operating speed ranges and reducing complexity and costs associated with DC-powered VFD systems.

Implementation Method 1

The VFD is operable to receive a 3-phase AC power having a first set of electrical attributes from at least one of the one or more AC power source, convert the received 3-phase AC power into AC power or DC power having a second set of electrical attributes and supply the AC or DC power having the second set of electrical attributes to the compressor and/or the one or more fan

Methodology Applied

Scientific EffectPower conversion:

Data Source

PatentUS12525911B2System and method for operating variable frequency drive using AC-power source in transport refrigeration unit

Publication Date: 2026.01.13 CARRIER CORP

AI summary

A system in a transport refrigeration unit (TRU) for driving a compressor and/or fan(s) of the TRU by a variable frequency drive (VFD) that is operable using AC power comprises the VFD operatively connected between the compressor and one or more ac power source such as an engine-generator assembly of the TRU and/or an electrical grid. The same VFD or a different VFD is also operatively connected between the AC power source and fan(s) associated with an evaporator, and a condenser of the TRU. The VFD is configured to be operated by the AC power sources. The VFD is operable to receive a 3-phase AC power ranging from 200 to 650 volts and 0.25 to 25 KW from at least one of the AC power source, convert the received 3-phase AC power to supply AC or DC power to a motor associated with the compressor and/or the fan(s).