Electric Compressor Brake Control to Prevent Switching Element Damage
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Solution Overview
Problem
Existing electric compressors face issues with sudden stoppage of the compression mechanism leading to excessive current flow in the inverter circuit, potentially damaging switching elements due to regenerative current during brake control.
Innovation Solution
An electric compressor with a control unit that detects current flow and adjusts the drive pattern of switching elements to prevent current from exceeding a predetermined threshold, ensuring safe shutdown and preventing damage by turning all elements OFF when current is high and adjusting the drive pattern when current is low.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If brake control is performed by turning all switching elements OFF and then energizing predetermined switching elements to apply load to the motor, then the compression mechanism can be stopped quickly, but excessive current may flow in the inverter circuit potentially damaging the switching elements
Solution Approach 1:
The control unit continuously monitors the current flowing through the inverter circuit during brake control and uses this feedback to dynamically adjust switching element operation. When current exceeds the first threshold, the control unit turns all switching elements OFF to prevent damage. This closed-loop feedback mechanism enables both quick stopping and protection of switching elements from excessive current damage.
Solution Approach 2:
The control unit changes the operational parameters of switching elements based on real-time current conditions. By adjusting which switching elements are ON or OFF depending on whether current is below or above the first threshold, the system optimizes the balance between stopping speed and switching element protection, resolving the contradiction between quick stopping and reliability.
2Reliability
If the drive pattern of switching elements is adjusted to prevent current from exceeding a lower second threshold, then switching elements are protected from damage, but the stoppage time increases
Solution Approach 1:
The control unit dynamically adjusts the drive pattern of switching elements based on real-time current monitoring. Rather than using a fixed conservative approach, the system adapts its braking strategy: when current is below the first threshold, it applies stronger braking to reduce stoppage time; when current approaches the first threshold, it reduces braking intensity to prevent exceeding the second threshold. This dynamic adjustment resolves the contradiction between protection and stopping time.
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
Effectively prevents damage to switching elements by controlling current flow, allowing quick and safe stoppage of the compression mechanism, thereby reducing the risk of reverse rotation and abnormal noise.
Implementation Method 1
a current detection unit that detects a current flowing through the motor drive circuit
Implementation Method 2
the rotational energy of the compression mechanism appears as a current flowing in the circuit of the inverter (which can also be called the regenerative current)
Data Source
AI summary
The present invention quickly stops rotation of an electric compressor while preventing damage to switching elements. An electric compressor 1 comprises a motor drive circuit 52 having multiple switching elements IGBT Q1 to Q6, a control unit 53 that controls driving of the multiple switching elements IGBT Q1 to Q6 and drives a motor 4, and a current detection unit 54 that detects a current flowing through the motor drive circuit 52. The control unit 53 performs stop control that stops rotation of the compression mechanism 3 by performing braking control that controls drive of predetermined switching elements IGBT (Q2, Q4, Q6 and the like) among the multiple switching elements IGBT Q1 to Q6. In the brake control, when the detected current value I is lower than the first threshold I1, the control unit 53 adjusts the drive pattern of the predetermined switching elements IGBT (Q2, Q4, Q6 and the like) in order to prevent the detected current value I from exceeding the second threshold I2 that is lower than the first threshold I1.