Solutions for overcurrent during the startup of power-frequency refrigerant compressors
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Is anyone still here? I recently tried to start a 8000 KW motor for an industrial-frequency compressor. I was able to start it successfully once before; the inlet pressure was 1.5 kilograms, and the gas mixture consisted mainly of methane and ethylene. The anti-surge valve was set to its maximum position while the outlet valve was closed. Yet the starting current reached 1000 A, causing the system to shut down twice. Even after shutting down all of the plant’s high-power equipment before attempting to start the compressor, it didn’t work. Are there any good strategies for starting this compressor successfully?
Equipment rated at 380V is equipped with soft starters, which result in a longer start-up time; the starting current is relatively low, approaching the current level during normal operation. However, for such large motors of 8000kW, high voltage is definitely used, so it’s difficult to determine the exact value in this case
The set value is 250% of the rated current; as a result, it reaches over 1000 amperes right away, and the value jumps immediately – I don’t dare set it any higher
The CT transformation ratio is 1000:5, right? Around 500 currents for 8000 kW, which is normal. What is the starting method, and what is the value of the start-up delay? This is a comprehensive issue; the equipment itself is fine. You guys in electrical engineering should understand this. What fault does the protection device report when the system shuts down?
Our factory is equipped with an inverter for variable-frequency starting
For direct starting at line frequency, it is necessary to evaluate the impact of the starting current on the system:
May I ask what the motor’s rated current is, and what the voltage is – 6 KV? Generally, it is started directly, and the starting current can reach about 5 times the rated current. Has the electrical engineering team taken into account the impact of direct starting on the power grid during the design phase?
Generally, variable frequency drives are used to control the startup