Reciprocating compressor motor starts with overflow trip
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The motor of the reciprocating compressor experiences overcurrent during startup, preventing it from starting. Upon startup, the motor must wait until it trips and stops before pressing the start button; only then can it start due to inertia. It’s no problem to disconnect the motor with no load. The operating current is normal upon startup.
At the moment of startup, the current in reciprocating compressors rises to 8 times the rated value. This is a common problem with all large motors; therefore, do not apply any load at the moment of startup. Let it run idle for a few minutes until the current stabilizes, and then apply the load
Startup overload. Such equipment needs major repairs. The reasons for startup overload include the need to start the oil pump and turn the shaft manually prior to startup, so as to lubricate the bearings. Excessively low ambient temperature can also cause overloading. Otherwise, a major repair will be necessary. For reference.
Check whether there’s a problem with the unloader; the situation you described is very likely due to starting the machine under load
The other one started normally without using a unloader
Is it starting under pressure? Starting under pressure results in extremely high current during startup. Another possibility is that the selected motor is underpowered. Normal operation under no-load conditions does not necessarily mean that the selection is appropriate. It is recommended to contact the motor manufacturer to determine whether the chosen motor is suitable
The reactivated one hasn’t been used for over half a year