How to perform a DC hipot test?

IC Capacitive

Capacitive current, also known as geometric capacitive current, refers to the inrush current that occurs due to the capacitance of the windings. Current is necessary to increase the voltage potential. Typically, capacitive current decreases to zero within seconds after the test voltage from the motor tester stabilizes.

You will receive efficient and thoughtful service from Hengfeng.

IA Absorption

Absorption current occurs during the atomic and molecular polarization of insulation and is a key current during a Polarization Index (PI) test. This current may drop to zero, or nearly zero, over varying periods depending on the motor, ranging from seconds to more than 10 minutes.

IG Volume Conduction

Volume conduction current flows through the entire volume of insulation located between the ground and conductors. In well-functioning windings, this current is generally zero or close to zero, depending on the insulation system's composition and condition. This current is sometimes equated with leakage current, though in used motors, surface conduction current (IL) mainly accounts for the leakage.

IL Surface Conduction

Surface conduction current, often termed surface leakage current, travels along the insulation’s end winding surfaces.

For more information on the 320KV DC hipot tester, please contact us, and we will provide professional answers.

• Surface conduction arises from contaminants, dirt, and moisture on grounded windings.
• With increased contamination, the resistance decreases, leading to a rise in current.
• As voltage increases, current typically escalates proportionally with the voltage applied by the motor tester.
• In used motors, this current often overshadows the absorption and volume conduction currents due to comparatively lower resistance in surface contamination.
• For new, thoroughly clean, dry motors, this current should be either zero or nearly zero.

How DC Hipot Tests Work

During a DC hipot test, a DC over-voltage potential is applied to the windings while measuring the current to ground with a resolution of 1 pA for the iTIG and 10 nA for the Power Pack. This current comprises leakage from the windings along with surface currents on the windings’ exterior. For more details on various leakage currents, refer to Insulation Resistance Measurement Methods.

The test voltage varies based on the condition of the Device Under Test (DUT), typically ranging from about 2E to 3.4E+V, where E corresponds to the RMS operating voltage of the DUT.

The iTIG tester features three possible failure modes that can terminate the test:

1. The over-current trip-out threshold is surpassed, a level that can be preset in μA by the user.
2. An arc is detected between the windings and ground.
3. The current to ground accelerates beyond the set rate of change (ROC) limit established for a step voltage test.

Can a DC Hipot Test Be Destructive?

DC hipot tests involve applying a voltage that exceeds the DUT's operating voltage, thus they are termed over-voltage tests. When conducted correctly, these tests are not destructive. Their non-destructive nature primarily stems from the test voltage being significantly lower than the insulation design voltage. Additionally, the available energy is dictated by the applied voltage and the system's capacitance, which is relatively low. Should an arc occur due to weak insulation, the low energy involved typically would not damage the insulation, unless the test is performed under unsuitable conditions for over-voltage tests.

The company is a leading 340KV DC hipot tester supplier. We are your one-stop shop for all related needs. Our specialized staff will assist you in locating the product you require.