Turn-to-turn failure is a problem that cannot be avoided in the production process of hydraulic oil pump motors. Large enterprises are equipped with turn-to-turn testers, but small enterprises and repair companies may not have this equipment. Therefore, the simple FM test method is very effective of. Just check it out with the editor of Dalan Motor.
1. Inter-turn fault appearance
After an inter-turn short-circuit fault occurs in the stator winding of the motor, the short-circuit turn generates an induced electromotive force under the action of the alternating magnetic field inside the motor. Since the short-circuit turns form a loop and the resistance is very small, the induced potential generates a large current in the short-circuit loop. This current can be as high as several times the rated current, causing the temperature of the short-circuit turn to increase.
Second, the working principle of the traditional impulse interturn instrument
In the current detection method, a turn-to-turn voltage tester is often used to diagnose winding turn-to-turn faults. It is based on the basic principle of the symmetrical balance of the impedance of the three-phase winding of the motor stator. The high-voltage pulse is used to perform an equivalent overvoltage simulation test on the winding, that is, the shock wave comparison method is used for detection. Observe the waveform and comparative analysis through the display of the tester. When there is insulation breakdown between the turns, the waveform on the display appears burrs and jumps, and the waveform does not overlap.
3. Frequency modulation method to measure the inter-turn faults of motor windings
When the withstand voltage of the traditional impulse impulse non-destructive test cannot be implemented due to no instrument or instrument failure, it has to seek to compare and distinguish through other methods. One of the most simple and practical methods is the frequency modulation detection method.
Principle: When there is a small number of turns between turns in a certain phase winding of the stator, the inductance is reduced compared with normal, the reduced inductance is very small, and the resulting three-phase difference is not as large as the surrounding interference, making the traditional impulse interturn test impossible The faulty phase is detected.
If the frequency of the test power supply is increased, the circulating current within a few turns of the short-circuit fault will increase, and then a dramatic change will occur:
(1) Increased three-phase difference;
(2) Local overheating intensified.
Therefore, there are the following favorable factors for judging the short-circuit fault between turns:
(1) The faulty phase in the three-phase winding is easily detected;
(2) Easy to determine the fault location-just touch which tooth groove is warm.
----- Responsible Editor: Dalan Oil Pump Motor 02-Procurement Consultant
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