Fault detection method and apparatus for three phase power supply circuit of frequency converter, and air conditioner

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Solution Overview

Problem

Existing fault detection methods for three-phase power supply circuits in frequency converters and air conditioners require separate detection circuits that introduce high-power resistors, causing heating and occupying large PCB areas, and cannot quickly determine fault types based solely on the main loop.

Innovation Solution

A method and apparatus that increase the current or power of the load in the three-phase power supply circuit to detect fault types by analyzing the frequency of the ripple voltage of the bus voltage, allowing quick determination of faults such as three-phase imbalance and phase missing without additional detection circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a separate fault detection circuit is introduced to detect three-phase power supply faults, then the fault detection capability is improved, but the device complexity and PCB area increase due to additional high-power resistors and detection components

Engineering Contradiction:

Improvefault detection capabilityVSAvoidcircuit structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The fault detection function is merged with the existing main control loop of the frequency converter. The same current sensor and voltage sensor used for normal operation are utilized for fault detection, eliminating the need for separate detection circuits and high-power resistors. The control processor integrates both operational control and fault detection processing.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The existing sensors and control processor are made multi-functional, serving both normal operational control and fault detection purposes. The current sensor detects both operational current and fault conditions, the voltage sensor monitors both operating voltage and fault voltage, and the control processor handles both control algorithms and fault analysis.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If high-power resistors are used for voltage reduction in the detection circuit, then the voltage detection accuracy is improved, but serious heating occurs and energy loss increases

Engineering Contradiction:

Improvevoltage detection accuracyVSAvoidheating and energy loss

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The mechanical/electrical voltage division method using high-power resistors is replaced with an electronic measurement approach. The voltage sensor directly measures the bus voltage without requiring physical voltage reduction, and the control processor digitally processes the voltage signal, eliminating resistive heating and energy loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If the load current or power is increased to improve fault detection sensitivity, then the fault detection accuracy is improved, but the normal operating conditions may be affected

Engineering Contradiction:

Improvefault detection accuracyVSAvoidnormal operation stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The fault detection is performed periodically by analyzing the ripple voltage frequency characteristics during normal operation. The control processor continuously monitors the bus voltage ripple frequency without injecting additional test signals or altering load conditions, enabling fault detection while maintaining normal operational stability.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system uses feedback from the existing voltage and current sensors to continuously monitor operational parameters. The control processor analyzes the feedback signals for ripple voltage frequency characteristics that indicate faults, allowing detection without disrupting normal operation. The system adapts its monitoring based on operational conditions.

Inventive Principle:

Principle #23Feedback

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

Enables rapid and efficient fault detection in three-phase power supply circuits by analyzing ripple voltage frequency, reducing the need for separate detection circuits and minimizing heating and PCB space usage.

Implementation Method 1

determining, according to a frequency of a ripple voltage of a bus voltage of the three-phase power supply circuit with increased load, a fault type of the three-phase power supply circuit

Methodology Applied

Scientific EffectRipple voltage:

Data Source

PatentUS12566219B2Fault detection method and apparatus for three phase power supply circuit of frequency converter, and air conditioner

Publication Date: 2026.03.03 HEFEI MIDEA HEATING & VENTILATING EQUIP

AI summary

A fault detection method and apparatus for a three-phase power supply circuit of a frequency converter, and an air conditioner. The fault detection method for the three-phase power supply circuit of the frequency converter includes: when a fault occurs in the three-phase power supply circuit, increasing a current or power of a load of the three-phase power supply circuit; quickly determining a fault type of the three-phase power supply circuit according to a frequency of a ripple voltage of a bus voltage. In this way, the fault type of the three-phase power supply circuit can be quickly determined simply based on the main loop of the three-phase power supply circuit.