Questions about the three-phase current of the motor?
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For a 30kW three-phase asynchronous motor, the operating currents are 52A for phase A, 43A for phase B, and 38A for phase C. There is no alarm indicating current imbalance in the motor controller. Is this operating current normal? What causes such a large difference between the three phases?
It’s probably a problem with the motor’s insulation…. In the case of regenerative motors, issues such as drying out and inadequate insulation can occur due to improper reinstallation. Or maybe the motor is damp,,, It is recommended to try drying it again, for reference.
Ahaha, let me explain! Firstly, the three-phase current imbalance (under load) has already exceeded 3%, which is above the acceptable limit; this will also lead to increased motor vibration. It is recommended to schedule a shutdown for inspection and repair; otherwise, the motor windings may get burned out over time! The main reasons can be analyzed from three aspects: 1. It is caused by an unbalanced voltage in the three-phase power supply; it is necessary to check whether there are issues such as poor contact, oxidation, or looseness in the contacts of the switching elements in the distribution circuit ； 2. There is an inter-turn short circuit fault in the stator windings; the machine can be shut down to check whether the DC resistances of the three-phase windings are balanced ； 3. There may be loose connections or oxidation between the power supply and the motor, or among the various terminals of the motor; open the wiring box and check each connection individually to address the issue.
It’s not compared to the rated current. Check whether the currents of the three-phase motor are balanced; the difference between the current of any one phase and the average value of the three-phase currents must not exceed 10%. If this value is exceeded, it indicates that there is a fault with the motor, and the cause must be identified and measures taken.