Problem of the low-frequency standby pump for the liquid oxygen pump
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Ladies and gentlemen, let me first explain the situation: we use three liquid oxygen pumps to supply oxygen to our customers, with two in operation and one as a backup; the backup pump operates at a low speed of 1100 RPM. The problem encountered at present is that when the customer starts up the large equipment, the voltage of the entire power grid drops, causing the current flowing through this pump in low-frequency mode to surge (from 70A to 150A). As a result, the flow rate at the pump’s outlet (the backflow) also increases (from 7500 to 15000). Eventually, the flow rate exceeds the requirements specified for low-frequency operation, which leads to the pump shutting down. (The pump’s output hasn’t changed at all.) Please help me figure out what the problem is. We are using AB frequency converters.
When a frequency converter encounters low voltage, the current increases~~As the voltage slowly returns to normal, the flow rate at the pump outlet rises~~Typically, the low-voltage protection threshold for frequency converters is set at 85%; frequent occurrences of low voltage along with high currents can reduce the motor’s service life~~