Motor Controller Modulation Switching for Compressor Electric Leak Prevention

Solution Overview

Problem

Motor-driven compressors face issues with electric leaks due to exposure to liquid refrigerant, particularly when using two phase modulation control, which increases the likelihood of leaks compared to three phase modulation control, and also experiences higher inverter losses.

Innovation Solution

A motor controller that determines the presence of liquid refrigerant and switches between three phase and two phase modulation controls to minimize electric leaks and inverter losses, with the three phase modulation control used when refrigerant is present to reduce voltage fluctuation at the neutral point and the two phase modulation control used when refrigerant is not present to reduce inverter losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If two phase modulation control is used to reduce inverter losses, then energy efficiency is improved, but the likelihood of electric leak increases when liquid refrigerant is present

Engineering Contradiction:

Improveinverter lossesVSAvoidelectric leak risk

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The system dynamically switches between two-phase and three-phase modulation control modes based on real-time detection of liquid refrigerant presence. When liquid refrigerant is detected, the system transitions from two-phase control (lower energy loss) to three-phase control (lower electric leak risk), and vice versa when liquid refrigerant is absent. This dynamic adaptation resolves the contradiction by allowing the system to optimize for energy efficiency under normal conditions while ensuring safety when liquid refrigerant accumulation occurs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the control parameter (modulation control mode) based on the detected state of liquid refrigerant. By monitoring the neutral point voltage or current characteristics to detect liquid refrigerant presence, the system adjusts the modulation strategy accordingly. This parameter change enables the system to balance between energy efficiency and electric leak prevention by selecting the appropriate control mode for each operating condition.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If three phase modulation control is used to reduce electric leak risk, then safety is improved, but inverter losses increase compared to two phase modulation control

Engineering Contradiction:

Improveelectric leak preventionVSAvoidinverter losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The system dynamically switches between two-phase and three-phase modulation control modes based on real-time detection of liquid refrigerant presence. When liquid refrigerant is detected, the system transitions from two-phase control (lower energy loss) to three-phase control (lower electric leak risk), and vice versa when liquid refrigerant is absent. This dynamic adaptation resolves the contradiction by allowing the system to optimize for energy efficiency under normal conditions while ensuring safety when liquid refrigerant accumulation occurs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the control parameter (modulation control mode) based on the detected state of liquid refrigerant. By monitoring the neutral point voltage or current characteristics to detect liquid refrigerant presence, the system adjusts the modulation strategy accordingly. This parameter change enables the system to balance between energy efficiency and electric leak prevention by selecting the appropriate control mode for each operating condition.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If voltage control is used to prevent electric leaks by lowering voltage when liquid refrigerant is accumulated, then electric leak risk is reduced, but control complexity increases

Engineering Contradiction:

Improveelectric leak preventionVSAvoidcontrol complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of directly controlling voltage levels to prevent electric leaks, the invention inverts the approach by switching between two-phase and three-phase modulation control modes. The three-phase mode inherently provides lower voltage fluctuation at the neutral point, which naturally reduces electric leak risk without requiring explicit voltage control mechanisms. This inverted approach simplifies the control system while maintaining electric leak prevention effectiveness.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8834131B2Motor-driven compressor and controller therefor

Publication Date: 2014.09.16 TOYOTA INDUSTRIES CORP

AI summary

A motor controller for a motor-driven compressor includes a compressing body for compressing and discharging a refrigerant and a motor including a rotary shaft, the motor for driving the compressing body through the rotary shaft. A coil of the motor is arranged in a refrigerant containing area in the motor-driven compressor. The motor controller includes a determining section for determining whether liquid refrigerant is present in the refrigerant containing area and a modulation control section for driving the motor in accordance with three phase modulation control or two phase modulation control based on a determination result of the determining section.