Testing IGBTs

Preamble

Inside a broken Electrolux induction hotplate, ETD28KS, there is a IGBT, H20R1203. Other hotplates I had tried to fix were MOSFETs that controlled the current to the heating coil, see Fixing a hotplate.

Most videos on YouTube or web guides seem to focus on IGBT packages, the large black blocks, that contain two IGBTs, and refer to C2/E1.

However, I want to test only one single IGBT, not a pair.

This is the hotplate

This is the IGBT

This is the PCB (the IGBT is bottom left):

The package showing the leads and Gate, Collector and Emitter:

The Gate of an IGBT takes little or no current, only a voltage control. The Collector-Emitter (CE) junction carries the high current.

This differs from the Base of a BJT which is current controlled.

Links

Videos

Guides

  • Testing an IGBT – This seems to contain an error at 1.2. The check should be from C1 to C2/E1 (and not C2/E1 to C1 as this will show a diode voltage drop). However, this may be checking that the diode itself is not shorted. In that case the leads should be reversed on both checks for shorts, to check for short across the diode and across the CE junction.

Notes

First video

From How to test an IGBT with a Multimeter

First test – Collector Emitter Junction test

  1. Short the Gate and Emitter
  2. DMM in Diode mode
  3. Positive lead to Emitter, Ground lead to Collector
  4. Diode drop expected
  5. Positive lead to Collector Ground to Emitter
  6. Open circuit

Second test – Gate oxide test

  1. DMM in diode resistance mode
  2. Gate to Collector resistance- should be open circuit
  3. Gate to Emitter resistance – should be open circuit

Second video

From How To Test an IGBT, it is pointed out that there is a diode from Emitter to Collector, as shown in the datasheet for the H20R1203:

Hence the diode voltage drop across EC, in step 4 of the first test (Collector Emitter Junction test).

First test – Ground short

  1. DMM on Diode check
  2. Short gate and emitter to remove any charge from the gate.
  3. Positive to ground, negative lead to gate, collector, emitter
  4. All three should be open circuit

Gate Emitter check

  1. Short gate and emitter to remove any charge from the gate.
  2. Test gate (positive lead) to emitter (negative lead)
  3. Should be open circuit (DMM diode check voltage is three voltage max and not enough to turn on IGBT)

High current check

  1. Short gate and emitter to remove any charge from the gate.
  2. positive lead to collector
  3. Negative lead to emitter
  4. Expect to see open circuit
  5. positive lead to emitter
  6. Negative lead to collector
  7. Expect to see diode voltage drop – a short circuit is very bad and IGBT is fried.

Gate to anything

  1. Short gate and emitter to remove any charge from the gate (optional for this test, but still good practice).
  2. Positive lead to Gate,
  3. Negative lead to Collector and Emitter.
  4. Expect to see Open circuit on both
  5. Reverse leads: Negative lead to Gate
  6. Positive lead to Collector and Emitter
  7. Expect to see Open circuit on both – again

Charged gate

  1. Negative lead to emitter
  2. Positive lead to Gate – now the gate is charged
  3. Positive lead to collector
  4. Negative lead to emitter
  5. You should see a voltage drop (~0.45 V) as current is now passed from collector to emitter

Possible faults:

  • Bad transistor has short from gate to emitter – 0.013 V dropped

Guide

This guide, Testing an IGBT, is useful, but a little confused for the shorted check. Also if it is checking resistance then the DMM should be on a resistance setting and not diode. This is how I would use it:

1. CHECK FOR SHORTED IGBT
Using a digital ohmmeter on the resistance scale:

  1. Measure resistance between C2/E1 and E2. Reverse leads and check again.
  2. Measure resistance between C1 and C1. Reverse leads and check again.

If you measure a short (0 ohms) in step 1a. or 1b., the IGBT is not usable.

2. TURN ON Q1, Q2
Using a digital ohmmeter on the resistance scale:

  1. Touch the + (red) meter lead to G1 and the – (black) to E1.
  2. Touch the + (red) meter lead to G2 and the – (black) to E2.
  3. Measure resistance between C1 and C2/E1. Should read a low resistance (about a diode drop). Reverse meter leads, reading should be the same.
  4. Measure resistance between E2 and C2/E1. Should read a low resistance (about a diode drop). Reverse meter leads, reading should be the same.

3. TURN OFF Q1, Q2
Using a ohmmeter on the resistance scale:

  1. Touch the + (red) meter lead to E1 and the – (black) to G1.
  2. Touch the + (red) meter lead to E2 and the – (black) to G2.
  3. Measure resistance between C2/E1 (+) and C1 (-). Should read a low resistance (same as in step 2c.). Reverse meter leads. Read infinite resistance.
  4. Measure resistance between C2/E1 (-) and E2 (+). Should read a low resistance (same as in step 2d.). Reverse meter leads. Read infinite resistance.

Note: Some digital ohmmeters do not have enough power to turn on an IGBT. A 9 volt battery may be used instead.

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