Zhuzhou Zhirong Advanced Material Co., Ltd , https://www.zrcarbide.com
According to the analysis of the burned three-phase motor, Dalan motor manufacturers know that no matter what type of motor is connected, when the motor lacks phase, it can still continue to run, but the speed of the motor will decrease and the slip will become larger. Next is the cause analysis and corresponding countermeasures.
One, two kinds of wiring analysis are as follows:
(1) When the winding of three-phase asynchronous motor is Δ connection
In operation, it is assumed that when the B-phase power supply is disconnected, the two-phase windings of B and C become serially connected in parallel with the A phase. Under the condition of constant load, the current of the A phase is too large, and the long-term operation, the winding of this phase is inevitable Overheated and burned. The same is true in actual work. If the motor's one-phase or two-phase windings burn out (or overheat), they are generally caused by the lack of phase operation.
(2) When the three-phase asynchronous motor winding is Y-connected
After the power supply is out of phase, the motor can continue to run, but also the speed drops significantly, the slip becomes larger, and the speed of the magnetic field cutting conductor increases. At this time, the B-phase winding is opened, and the two-phase windings of A and C become serial and pass Excessive current and long-term operation will cause the two-phase winding to burn out at the same time.
When a stopped motor is closed without a one-phase power supply, it will generally only hum and cannot be started. This is because the symmetrical three-phase AC power applied to the motor will produce a circular rotating magnetic field in the stator core, but when one phase is missing After power is supplied, a single-phase pulsating magnetic field is generated in the stator core, which cannot cause the motor to generate a starting torque. Therefore, not only can the motor not start when the power supply is phase-deficient, but the phase-closing will produce a locked rotor current several times the rated current in the motor windings, and the winding burn-out speed will be faster and more serious than the sudden phase loss during operation. The operator must pay attention to this.
Second, the corresponding countermeasures:
From the above analysis of Dalan motor manufacturers, we know that no matter whether the motor is static or dynamic, the direct harm caused by the lack of phase operation is that the one-phase or two-phase windings of the motor are overheated or even burned out. At the same time, the over-current operation of the power line (cable) also accelerates the aging of the line insulation. Therefore, in order to ensure the safe operation of the motor, so that it can stop the operation of the motor in time when the phase loss operation occurs, to avoid causing motor burnout accidents, generally important motors are equipped with protection devices. However, most of the current motor phase loss protection circuits use microcomputer protection or electronic protection devices, which have many components, complicated circuits and low working reliability. When problems occur, they often lose protection or work abnormally, causing the motor protection to refuse to operate. Or it cannot be closed.
----- Responsible Editor: Dalan Oil Pump Motor 02-Procurement Consultant
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