An IGBT or insulated gate bipolar transistor is a semiconductor component used to power many home appliances and vehicles. If an appliance appears to be short-circuiting, you can perform a test to determine if the IGBT is the culprit. If performed successfully, this can save having to replace the appliance and instead replace the faulty IGBT. It is important to pay close attention and take care when performing this test, however, as applying excessive heat or voltage to the IGBT can be dangerous and cause irreparable damage to the appliance.

Finding a faulty IGBT can save the expense of replacing the entire circuit on an appliance.

Step 1

Unplug the appliance. Locate the IGBT in the circuitry. It is a black or white circuit brick with two connections on the side and two to six connections on top. Location on the circuit board will vary by appliance.

Step 2

Remove the IGBT from the appliance by unscrewing the four screws at the corners. Do not perform any test procedures until all electronic connections have been removed from the IGBT to ensure safety.

Step 3

Check the condition of the protection diode using DMM (digital multi meter) in diode test mode. Take the red lead of the DMM and attach it to the black lead on the IGBT. This is the emitter terminal. If the reading on the DVM is between .2 and .8, the IGBT has a functional protection diode.

Step 4

Take a digital multi-meter (DMM) and set it in resistance mode. Attach it to the emitter on the IGBT (the black lead). If the device displays anything but an infinite reading you may have a shorted IGBT. This is known as a gate-oxide test.

Step 5

Test the functionality of the IGBT by taking an IGBT tester and attaching it to the gate, collector and emitter terminals on the IGBT. The gate will be on the side of the device near the emitter while the collector is on the opposite side. This should be all three leads on the device. Press the test button on the tester and check if the conduction light is on. If it does not light, the IGBT may be faulty.

Step 6

To be sure a protection diode is not interfering, switch the collector and emitter leads but DO NOT hit the test button. If switching the leads causes the conduction light to turn, on the IGBT has a functional production diode.