How do you find the PI of a transformer?

How do you find the PI of a transformer?

In PI test, ratio of insulation resistance at different times after starting of test is recorded. The DC voltage is applied between conductors and insulating part, and the insulation resistance value is recorded after 1 minute, then test is continued and the insulation resistance value after 10 minutes is recorded.

How do you test polarization index?

From a standpoint of physics, to polarize is to cause something to obtain polarity. The test involves applying a positive charge to motor conductors and a negative charge to the motor frame, therefore polarizing the insulation. The test effectively measures a change current over time.

What is pi testing?

PI Test is a personality test administered by employers to evaluate how suitable a potential employee is for the role they applied for in an organization. Potential employees are subjected to Predictive Index Behavioral Assessment (PIBA) and Predictive Index Cognitive Assessment (PICA).

What is pi value of power transformer?

Interpretation of Polarisation Index results
PI Condition of item under test
1 – 1.5 Bad
1.5 – 2.0 Doubtful
2.0 – 3.0 Adequate

What is pi value of motor?

A minimum PI value of 2.0 is necessary for induction motors. The life and performance of a motor depend largely on the windings’ insulation conditions. This is why it is necessary to determine the insulation condition through tests such as the polar index tests and insulation resistance (IR) testing.

What is Megger pi?

A Megger commonly gives readings in ohms of resistance. A hipot registers the amount of current (typically in microamps (mA). One microamp is equal to 1 x 10-6 amps, or 0.000001 amps. The Polarization Index is derived by the ratio between the one minute reading and the ten minute reading.

What is a good polarization index?

The Polarization Index is derived by the ratio between the one minute reading and the ten minute reading. Recommended minimum PI results for suitability for service (or implementation of high voltage testing) is widely accepted as 2:1 or greater. Any reading lower than this minimum value is a concern.

What do you mean by polarization index?

Polarization Index, or PI, is a ratio of the megohms after 10 minutes divided by the megohms after 1 minute. This test is primarily conducted on form wound motors and generators.

Can you fail the predictive index?

For instance, at The Predictive Index (PI) we recommend that our clients use assessments as one factor alongside their credentials, interview(s), and references when making hiring decisions. Simply put, there really is no “pass” or “fail.”

How do you perform a PI test?

Performing PI testing Apply a maximum dc voltage between the stator and conductor in the windings. Use a megohmmeter to measure the resistance. Obtain a reading at one and 10 minutes so the final value can be determined. Turn the power supply off after the readings have been received.

Why DC is used in Megger?

If we apply DC voltage then as we know Capacitor blocks the flow of DC, only leakage current due to imperfection of insulator will flow and hence the Resistance measured by Megger will actually represent Insulation Resistance. This is the reason, an Insulation Tester or Megger have DC voltage generator.