What Is Layer Short ?

A magnetic component whit a lot of winding. However, the coil will cause short when the insulation has problem.

If this happened, the magnetic field will be changed. This will affect the efficiency of whole system.

Why will short happened on winding ?

• The process of enameled wire

The process of painting may scratch the wire.

Crack on the wire.

• Winding Process

Hook/Our of order/ Envelop

Winding span

Tin attached

Why do we need impulse tester for producing motor/transformer?

• The small defection is hard to find at low voltage test station. As the DUT goes to the final assembly test, the defect may show up.
• This will higher the cost of production.
• Motor and transformer usually work under high voltage.
• If we add impulse test in the product line, this may prevent the malfunction or burn on motor.
• Impulse Test= Quality and product life test

7750 Series Technology of Detect Layer Short

“Pulse voltage and waveform comparison” is the way we detect layer short.

The pulse voltage is non-destructive/instant voltage that apply on both side of winding and detect the DUT without damage it. By compare the wave with the golden sample, we can judge the DUT.

When short happened on coil, it may change the parameter of inductance , capacitance, and resistance. The insulation ability reduce. Usually, the problem will be discover under high voltage.

Without the high voltage, the defection point is hard to be penetrated.

So, it’s hard to find the problem from inductance , capacitance ,and resistance.

By comparing the wave of damping attenuation between golden sample and DUT.

Damping wave under L/C resonate comes from the feature change of defect coil.

1. Inductance of coil
2. Q rate
3. Turn ratio of coil(voltage different)
4. Material of core
5. Layer short in the coil

7750 Provides 6 waveform comparison

• Area Comparison

When layer short happened, the loss of power on coil increase, the resonance damping coefficient increase, resonance amplitude decrease, the total area decrease. These are the basic parameters we check layer short.

By calculating and comparing the deference of area between golden sample and DUT.

Analysis the power loss by this data.

• Area Differential Comparison

Add up the difference between normal wave and DUT wave call “ Area differential”

When layer short happened, the inductance reduce(similar the transformer). The wave phase change and the area differential also change. This will show “fail” on the instrument.

However, the parameter might cause deviation because of the deviation of inductance, resonance phase shift.

(Silicon steel product such as motor and traditional transformer is not suitable)

By calculating and comparing the deference of area between golden sample and DUT.

To determine the degree of waveform overlap.

Compare the inductance by this mode.

• LAPLACIAN Comparison (corona waveform of high-frequency)

Poor insulation quality of the coil results in discharge under high voltage impact, causing rapid changes in the oscillation waveform. By employing the 7750 second-order differentiation algorithm, the maximum discharge capacity is obtained, effectively detecting quality issues related to electrical leakage caused by poor solder joints in the monolithic inductor.

electrical discharge or poor electrode welding

• CORONA Comparison

In pulse test, the insulation defect will cause discharge and create corona. This function is able to count the times that corona happened base on the degree of deviation.

Detect the discharge phenomenon on the coil.

• COMP Comparison

During high-voltage pulse testing of the winding coil, the self-insulation system gets damaged, resulting in sharp discharge. The occurrence of corona can be observed in the discharge curve through waveform display. This functionality allows for counting the frequency of corona events and determining their deviation level for assessment.

• FLUT Comparison

When there is inter-turn discharge occurring in the winding coil, the waveform will exhibit fluctuations or tremors. Therefore, the instrument quantifies the degree of waveform tremor as a numerical value for comparison.

7750 Power Function

• Voltage Compensation Function

MICROTEST 7750 features the Voltage Compensation Function. In order to reduce the possibility of misjudgment.

• Safety Test-BDV Mode (Breakdown Voltage Test)

MICROTEST 7750 supports breakdown voltage analysis function, which allows for setting the following parameters for the winding component:

– Starting voltage
– Ending voltage
– Minimum percentage of voltage rise at the starting voltage

In the second-order differentiation mode and corona count comparison mode, it determines whether the values exceed the set standard. This verifies the withstand voltage strength of the tested winding component.

• 7750 Support checking output voltage

• 7750 Impulse Tester 200MHz/9bit  High Impulse Test Sampling Rate