Igbt Test Procedures

!±8± Igbt Test Procedures

The term Igbt is an acronym for Insulated Gate Bipolar Transistor. It can be understanding of as a Transistor with a Mosfet front end. It has three terminals (or leads) labeled Gate, accumulator and Emitter. Some Igbt's have a built in safety diode. This diode is linked across the accumulator and Emitter terminals. It is added for transient voltage safety when the Igbt is switching Inductive loads.

When these devices are thought about 'suspect' it is vital to validate their doing straight through a functional test procedure. One of two methods can be used:

The first test method will validate the condition of the safety diode, and the resistance of the accumulator and Emitter terminals. It is not a definitive test, but will find 80% of all faulty devices. This is due to the fact that most faulty Igbt's show a low resistance or short across the accumulator and Emitter terminals when the gismo is stressed.

To perform this test will wish a Dvm (Digital-Volt-Meter). Set the Dvm to the Diode Test position, and confirm that the gismo tests as follows:

Attach the Red Lead of the Dvm to the accumulator concluding and Black Lead to the Emitter Terminal. Confirm an open circuit condition.

Attach the Red Lead of the Dvm to the Emitter concluding and Black Lead to the accumulator Terminal. Confirm an open circuit condition (Igbt without a safety diode). If the Dvm displays a forward voltage drop of 0.2 to 0.8 Vdc it means that the Igbt has a built in safety diode. Both of these results are normal test conditions and are used to confirm whether the Igbt has a safety diode, and if it does, whether it is functional or not.

The second test method will check the Igbt's functionality, by gating the device. To perform this test will wish an Igbt Tester. Confirm that the gismo tests as follows:

Attach the Igbt Tester leads to the Gate, accumulator and Emitter Terminals. Confirm that the gismo Conduction Led is not lit.

Press the Test Button, and confirm that the Conduction Led lights.

Reverse the accumulator and Emitter leads. Do not press the Test Button. If the Conduction Led lights the Igbt has a built in safety diode. This is a normal test condition for this type of device. If the Conduction Led does not light then the Igbt does not have a built in safety diode. This is also a normal test condition for this type of device.

It is leading to note that Functional test of the Igbt should all the time be performed when the gismo is out-of-circuit. In other words, it should be removed from the goods and have no other electrical connections in place, other than those outlined in the Test procedure.