Inverter Startup Frequency Ramping to Limit AC Component Current
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Solution Overview
Problem
Existing transport refrigeration units face challenges in safely and efficiently supplying electrical power during the startup process of electrical components, risking damage to other components.
Innovation Solution
An apparatus with a controller that operates an inverter in a protected startup mode, controlling output frequency and voltage to gradually increase until reaching a predefined operating frequency, while monitoring and maintaining output current and power within safe thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inverter supplies full power during startup, then the startup process is completed quickly, but other components may be damaged due to excessive current
Solution Approach 1:
The controller detects startup conditions before full power is applied and prepares a controlled startup sequence. The inverter enters protected startup mode in advance, gradually increasing output frequency and voltage from zero to rated values, preventing sudden current surges that could damage components while ensuring the startup process completes safely and efficiently
Solution Approach 2:
The inverter dynamically changes output parameters (frequency and voltage) during the startup process. The controller adjusts the output frequency from 0 Hz to the rated frequency (e.g., 50 Hz or 60 Hz) and correspondingly adjusts the output voltage from 0 V to the rated voltage, maintaining current within safe thresholds throughout the transition
2Speed
If the inverter increases output frequency rapidly, then the electrical component reaches operating speed quickly, but excessive current may damage the inverter
Solution Approach 1:
The controller continuously monitors the output current of the inverter during the startup process and uses this feedback to adjust the rate of frequency and voltage increase. When current approaches the maximum threshold, the controller slows down the ramp-up rate, and when current is well below the threshold, it can increase the ramp-up rate, optimizing both startup speed and safety
Solution Approach 2:
The inverter employs dynamic control of the output frequency and voltage ramp-up rate rather than a fixed linear increase. The controller adapts the startup profile in real-time based on load conditions, allowing faster startup when possible and slower startup when necessary to maintain current within safe limits
Data Source
AI summary
The present disclosure relates to an apparatus comprising a controller, an inverter, a load and a DC link. The DC link is coupled to the load and couplable to a power source. The load comprises an AC electrical component. The inverter is configured to provide an output voltage and an output current to the AC electrical component, the output voltage having an output frequency. The controller is configured to: evaluate a component startup criterion relating to whether the AC electrical component is performing a startup process; in response to a determination that the component startup criterion has been met, operate the inverter in a protected startup mode; and when operating the inverter in the protected startup mode, control the output frequency such that the output frequency increases with time until the output frequency reaches a predefined operating frequency.