What is the cause of the three-phase current imbalance of the motor?
Research and application of AC motors, the three-phase balance problem is always a topic that cannot be avoided. In order to synthesize a circular rotating magnetic potential, the three-phase windings must be designed to have a spatial angular difference of 120° and an equal impedance value. In the actual application conditions, if there is a problem of three-phase current imbalance, or the finger can be fixed in a single moment, or the situation deteriorates and lead to a serious accident, the reason is always difficult to say. Today, Xiaobian discusses the three-phase current balance problem, aiming at cracking the three-phase unbalanced current and its causes, and using and controlling the three-phase AC motor.
Why is the three-phase current unbalanced?
In theory, when a three-phase symmetrical voltage is applied to the motor, a three-phase symmetrical current should flow through the armature winding of the three-phase AC motor. But in fact it is far from simple: the grid is not a simple three-phase load, and the motor is unbalanced due to its own quality, load and maintenance, and the three-phase current may be unbalanced, causing heat and abnormal noise. Or a serious accident that burned the motor.
●The influence of grid voltage on motor current
For a three-phase motor, if the power supply voltage is not flat, there will be a reverse-sequence current magnetic field in the motor, and a large reverse-order torque will be generated, resulting in current unevenness. When the power supply voltage imbalance is 5%, the motor phase current may appear to be as high as 20%.
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