Capacitor Current Determination for Inverter Electric Compressors
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Solution Overview
Problem
Inverter integrated electric compressors face issues with excessive input current to capacitors, leading to potential failures, necessitating a technique to control the capacitor current within an appropriate range.
Innovation Solution
A current value determination device and method that calculates and determines whether the capacitor current is within an appropriate range using input voltage, motor rotation speed, and a predetermined determination model, with a controller adjusting the inverter to maintain the current within safe limits by defining a three-dimensional coordinate system and temperature-specific models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the inverter integrated electric compressor is used in a high temperature environment, then the compressor can operate in hot conditions, but the capacitor current becomes excessive which may cause capacitor failure
Solution Approach 1:
The patent changes the operating parameters by introducing a determination model that considers temperature, rotation speed, and voltage to calculate appropriate capacitor current thresholds. The controller adjusts the inverter output parameters dynamically based on the determined appropriate current range, resolving the contradiction between high-temperature operation and capacitor reliability
Solution Approach 2:
The patent implements a feedback mechanism where the capacitor current is monitored, compared against the determined appropriate range, and the inverter control is adjusted accordingly. This closed-loop control ensures the capacitor current remains within safe limits while maintaining compressor operation in high-temperature environments
2Reliability
If the capacitor current is controlled to an appropriate range, then capacitor failure is prevented, but the device complexity increases due to additional determination models and calculations
Solution Approach 1:
The determination model serves multiple functions: it determines appropriate capacitor current ranges, evaluates operating conditions, and guides control decisions. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in device complexity while maintaining capacitor reliability
3Power
If the capacitor current is increased to meet high power demands, then the power output is improved, but the capacitor may fail due to excessive current
Solution Approach 1:
The patent applies dynamics by making the capacitor current limit dynamic rather than fixed. The appropriate current range is determined based on real-time operating conditions (temperature, rotation speed, voltage), allowing the system to maximize power output when conditions permit while protecting the capacitor when conditions are unfavorable, thus resolving the contradiction between power output and capacitor reliability
Data Source
AI summary
A current value determination device provided with: a capacitor current computation unit for computing the capacitor current of a capacitor included in a high-voltage circuit that drives a motor, on the basis of the input voltage of an inverter included in the high-voltage circuit and the revolution speed of the motor; and a capacitor current determination unit for determining the value of capacitor current on the basis of the input voltage of the inverter, the revolution speed of the motor, the capacitor current computed by the capacitor current computation unit, and a prescribed model for determination.