How to use a multimeter to measure an IGBT module?
I. Judging the Polarity
First, set the multimeter to the R×1K gear. When measuring with the multimeter, if the resistance between one pole and the other two poles is infinite, and the resistance between this pole and the other two poles is still infinite after reversing the test leads, then this pole is judged to be the gate (G). Then measure the remaining two poles with the multimeter. If the measured resistance is infinite, and the resistance is smaller after reversing the test leads. In the measurement with a smaller resistance value, the pole connected to the red test lead is judged to be the collector (C), and the pole connected to the black test lead is the emitter (E).
II. Judging the Quality
Set the multimeter to the R×10K gear. Connect the black test lead to the collector (C) of the IGBT and the red test lead to the emitter (E) of the IGBT. At this time, the pointer of the multimeter is at the zero position. Touch the gate (G) and the collector (C) simultaneously with your fingers. At this time, the IGBT is triggered to conduct, and the pointer of the multimeter swings towards the direction of smaller resistance and can stop at a certain position. Then touch the gate (G) and the emitter (E) simultaneously with your fingers. At this time, the IGBT is blocked, and the pointer of the multimeter returns to zero. At this time, it can be judged that the IGBT is in good condition.
III. Any pointer-type multimeter can be used to detect the IGBT
When judging the quality of the IGBT, be sure to set the multimeter to the R×10K gear. Because the internal battery voltage of the multimeter in the gears below R×1K is too low, the IGBT cannot be turned on during the detection of its quality, and it is impossible to judge the quality of the IGBT. This method can also be used to detect the quality of power field effect transistors (P-MOSFET).
Detection of IGBT Modules in Inverters:
Set the digital multimeter to the diode test gear, and test the forward and reverse diode characteristics between c1 and e1, c2 and e2 of the IGBT module, as well as between the gate G and e1, e2 to determine whether the IGBT module is in good condition.
Take a six-phase module as an example. Remove the wires of the U, V, and W phases on the load side. Use the diode test gear. Connect the red test lead to P (collector c1) and the black test lead to U, V, and W in turn. The value displayed on the multimeter is the maximum. Reverse the test leads, connect the black test lead to P, and the red test lead to U, V, and W. The value displayed on the multimeter is about 400. Then connect the red test lead to N (emitter e2), and the black test lead to U, V, and W. The value displayed on the multimeter is about 400. Connect the black test lead to P, and the red test lead to U, V, and W. The value displayed on the multimeter is the maximum. The forward and reverse characteristics between each phase should be the same. If there are differences, it indicates that the performance of the IGBT module has deteriorated and it should be replaced. When the IGBT module is damaged, only the situation of breakdown and short circuit will occur.
Use the red and black test leads to measure the forward and reverse characteristics between the gate G and the emitter E respectively. If the values measured by the multimeter twice are both the maximum, it can be determined that the gate of the IGBT module is normal. If a value is displayed, it indicates that the performance of the gate has deteriorated, and this module should be replaced. When the forward and reverse test results are zero, it means that the gate of the detected phase has been broken down and short-circuited. When the gate is damaged, the voltage regulator tube on the circuit board that protects the gate will also be broken down and damaged.
