To test the winding fault of the hydraulic oil pump motor, Dalan Motor will teach you a simpler and more practical method!

Turn-to-turn faults are an unavoidable problem in the manufacturing process of hydraulic oil pump motors. Large enterprises are equipped with turn-to-turn testers, but small businesses and repair companies do not necessarily have this equipment. Therefore, the simple frequency modulation test method is very effective. of. Please check with the editor of Dalan Motor for details.

1. Inter-turn fault appearance

After an inter-turn short-circuit fault occurs in the stator windings of the motor, the short-circuit turns generate induced electromotive force under the action of the alternating magnetic field inside the motor. Since the short circuit turns into a loop by itself, the resistance is very small, and the induced potential generates a large current in the short circuit loop. The current can be as high as several times the rated current, which increases the temperature of the short-circuit turns.

Second, the working principle of the traditional shock pulse turn-to-turn instrument

In the current detection methods, the turn-to-turn withstand voltage tester is often used to diagnose winding turn-to-turn faults. It is based on the basic principle of the impedance symmetrical balance of the three-phase windings of the motor stator, using high-voltage pulses to perform equivalent overvoltage simulation tests on the windings, that is, using the shock wave comparison method to detect. Observe the waveform through the display of the tester and compare and analyze it. When there is an inter-turn insulation breakdown, the waveform on the display shows burrs and jumps, and the waveform does not coincide.

Three, frequency modulation method to determine the fault between the turns of the motor winding

When the traditional impulse pulse turn-to-turn non-destructive test withstand voltage cannot be implemented due to no instrument or instrument failure, other methods have to be used for comparison and distinction. One of the simplest and practical methods is the frequency modulation detection method.

Principle: When there is a short circuit between turns of a certain phase of the stator, the inductance is small compared with the normal one, and the three-phase difference caused is not as large as the surrounding interference, which makes the traditional shock pulse inter-turn test impossible. The fault phase is detected.

If the frequency of the test power supply is increased, the circulating current in a few turns where the short-circuit fault occurs will increase, and then dramatic changes will occur:

(1) The three-phase difference increases;

(2) Local overheating is aggravated.

Therefore, there are the following favorable factors for the judgment of the inter-turn short-circuit fault:

(1) The fault phase in the three-phase winding is easily detected;

(2) It is easy to determine the fault location-just feel which slot is warm.