Motor drive device, blower, compressor, and air conditioner
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Solution Overview
Problem
Conventional motor drive devices fail to reliably protect switching elements in converter circuits from overcurrents, which can lead to propagation of faults to other switching elements during short-circuit conditions.
Innovation Solution
A motor drive device is designed with a reactor, converter circuit, capacitor, and dual current detection systems to identify overcurrents in both alternating and direct currents, triggering a stop operation of the converter and inverter circuits to prevent fault propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If self-protection function of IPM is used to protect switching elements from overcurrent, then switching elements are protected from overcurrent, but overcurrent continues to flow through diodes and parasitic diodes causing fault propagation to other switching elements
Solution Approach 1:
The patent divides overcurrent detection into two separate detection systems: one for AC current in the converter circuit and another for DC current in the inverter circuit. This segmentation allows independent monitoring and protection of each circuit stage, preventing fault propagation by stopping operation when overcurrent is detected in either circuit.
Solution Approach 2:
The patent implements preliminary overcurrent detection by monitoring both AC current before it enters the converter circuit and DC current after conversion. By detecting overcurrent conditions early in the conversion process and immediately stopping operation, the system prevents harmful overcurrent from reaching and damaging switching elements through diode paths.
2Reliability
If drive signal stops being output to protect switching element from overcurrent, then switching element is protected, but current continues to flow through diodes causing another switching element to be adversely affected
Solution Approach 1:
The patent employs feedback mechanisms by continuously monitoring both AC and DC current levels and using this information to control the drive signals. When overcurrent is detected in either the converter or inverter circuit, the feedback signal immediately stops the drive output, preventing current from flowing through diodes and protecting other switching elements from adverse effects.
3Device complexity
If single overcurrent detection is implemented, then detection is simple, but overcurrent paths through diodes are not blocked reliably
Solution Approach 1:
The patent segments overcurrent detection into two independent detection systems: one for AC current in the converter circuit and another for DC current in the inverter circuit. This dual-detection approach reliably blocks overcurrent paths by monitoring both stages of the power conversion process, ensuring comprehensive protection despite increased system complexity.
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
The solution effectively blocks overcurrent paths through diodes and parasitic diodes, ensuring reliable protection of switching elements and preventing fault propagation, thereby enhancing the reliability of the motor drive device.
Implementation Method 1
a converter circuit connected to another end of the reactor, the converter circuit converting a first voltage into a direct current voltage, the first voltage being an alternating current voltage output from the alternating current power supply
Implementation Method 2
a capacitor for smoothing a second voltage, the second voltage being a voltage on a direct current side of the converter circuit
Data Source
AI summary
A motor drive device includes a reactor, a converter circuit, a capacitor, an inverter circuit, and overcurrent determination units. The converter circuit converts a first AC voltage output from an AC power supply into a DC voltage. The capacitor smooths a second voltage on the DC side of the converter circuit. The inverter circuit converts DC power stored in the capacitor into AC power. One of the overcurrent determination units determines overcurrent based on a detected value of the first AC current, flowing between the AC power supply and the converter circuit. Another overcurrent determination unit determines overcurrent based on a detected value of the second DC current, flowing between the converter circuit and the capacitor. The converter and inverter circuits stop operating when the determination result of one of the overcurrent determination units indicates an overcurrent.