test method

In electrical machines, the polarization index (PI) is a very important parameter for determining the quality of an electric motor's insulation. Insulation deteriorates with age.

Polarization refers to the ability of the charge carriers in the insulator to align themselves with the electric field—in other words, to polarize. The older the insulation, the poorer the mobility of the charge carriers. As a result, the electrical insulation capacity decreases and there Motor an increased likelihood of serious damage to Motor .

The force required to rotate the load carriers in the insulator can be measured in the form of a very low current during the high voltage test measurement.

The polarization of the charge carriers does not occur immediately after applying the TEST VOLTAGE, but can take up to 10 minutes. It is assumed that polarization is still in full swing one minute after the test specimen capacity has been charged. This means that the mobility of the charge carriers can be determined by the ratio of the current during vigorous rotation at the beginning to the reduced current after the rotations have been completed.

• • PI = current after one minute / current after 10 minutes

or alternatively

• • PI = insulation resistance 10 minutes /insulation resistance one minute

With a good insulator, the current has dropped four to five times after 10 minutes because all charge carriers have become polarized. This results in a high and therefore good PI (e.g., 4 to 5). With a poor insulator, the current has hardly changed after 10 minutes, as the immobile charge carriers can no longer be properly polarized. This results in a low = poor PI (e.g., 1.5). Such an electrical machine is in urgent need of maintenance.

After completing the polarization, the actual current through the insulation resistance is measured. If the insulation resistance electric motors is determined too quickly, the resistance will be displayed as too low, since the Capacitance test object is initially charged and then the polarization is measured.

What products does SCHLEICH supply SCHLEICH

• Individual test devices
• Combination testers (combination with other safety or surge voltage tests)
• Fully automated tests
• Test equipment with extensive, freely programmable matrixes
• Test equipment with automatic ramp
• test guns
• Testing equipment for various device classes

standards bodies

For legal reasons, we are often unable to make any binding statements regarding test conditions. The currently valid standards for the product to be tested are decisive for its application.

The standard may vary depending on the geographical location where the product is used. Further information can also be found at the institutes listed below.