HVAC Condenser Bus Voltage Control for Compressor Backspin

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Solution Overview

Problem

In HVAC systems, compressor motors can backspin due to high refrigerant pressure, generating excessive voltage that can damage electrical components, and existing solutions like mufflers and chopper resistors are not always effective in preventing damage.

Innovation Solution

The implementation of a PFC circuit and controllable bus voltage system that couples the condenser and compressor assemblies, allowing the condenser motor to dissipate power generated by the backspinning compressor motor, and using a condenser inverter to control the output voltage and motor speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If permanent magnet compressor motors are used to compress refrigerant, then compression efficiency is improved, but the motors may backspin at high speed generating excessive voltage that can damage electrical components

Engineering Contradiction:

Improvecompression efficiencyVSAvoidexcessive voltage damage

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful backspin energy into a beneficial braking torque by using the condenser motor as an electrical load. When the compressor motor backspins, it generates excessive voltage that is directed to the condenser motor through the inverter, causing the condenser motor to act as a brake on the compressor motor, thereby dissipating the harmful energy while protecting electrical components.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The inverter serves as an intermediary device between the compressor motor and condenser motor. It detects excessive voltage from backspinning and redirects this energy to the condenser motor, mediating the harmful effect by transforming it into a controlled braking mechanism rather than allowing direct damage to electrical components.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If mufflers and check valves are used to inhibit reverse refrigerant gas flow, then backspin is reduced, but device complexity and component count increase

Engineering Contradiction:

Improvebackspin inhibitionVSAvoidcomponent count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical backspin inhibition devices (mufflers and check valves) with an electrical control system. Instead of using mechanical components to physically block reverse flow, the system uses the inverter to detect and electrically control the condenser motor to provide braking torque, substituting mechanical complexity with electrical control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If chopper resistors are used to produce braking torque, then reverse rotation is inhibited, but energy is dissipated as heat and device complexity increases

Engineering Contradiction:

Improvereverse rotation inhibitionVSAvoidenergy dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

Instead of dissipating backspin energy as wasted heat through chopper resistors, the patent converts this harmful energy into useful work by driving the condenser motor. The condenser motor acts as an electrical load that converts the kinetic energy from backspin into mechanical work, thereby inhibiting reverse rotation while utilizing the energy rather than wasting it.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively prevents damage from backspinning by dissipating the generated voltage and controlling motor speed, eliminating the need for chopper resistors and mechanical check valves, thereby enhancing the safety and efficiency of HVAC systems.

Implementation Method 1

a PFC circuit for generating an output voltage, a condenser motor operatively coupled to a fan... a condenser inverter having an input coupled to the PFC circuit and an output coupled to the condenser motor for powering the condenser motor with the output voltage

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

allowing the condenser motor to dissipate power generated by the backspinning compressor motor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS8400090B2HVAC condenser assemblies having controllable input voltages

Publication Date: 2013.03.19 COPELAND LP

AI summary

Assemblies for HVAC systems and methods of operating HVAC systems are disclosed, including a method of operating an HVAC system having a condenser motor operatively coupled to a fan and a controllable bus voltage for powering the condenser motor. The method includes increasing the controllable bus voltage from a first voltage to a second voltage to increase a speed of the condenser motor.