IGBT can be identified and detected by pointer multimeter and digital multimeter. Before detection, the three pins of IGBT should be short-circuited and discharged to avoid affecting the accuracy of detection. The specific operation method is as follows:
1. Identify the pins
1) Set the pointer multimeter to the Rx1k block. During measurement, if the resistance value of one pole and the other two poles is infinite, and the resistance value of this pole and the other two poles is still infinite after changing the test leads, it is judged that this pole is grid G. Use a multimeter to measure the remaining two poles. If the measured resistance value is infinite, the measured resistance value is smaller after replacing the test leads. In the measurement with a smaller resistance value, the red test lead is connected to the collector C, and the black test lead is connected to the emitter E.
2) Set the digital multimeter to the diode block, use the red test lead to fix one electrode, and the black test lead to contact the other two electrodes in turn. If it shows about 0.7V twice, it means that the red test lead is connected to the gate G, and the tube belongs to the N-channel. If the overflow is displayed twice, it means that the red test lead is also connected to the grid G, but the tube belongs to the P channel. If it shows 0.3-0.6V at one time and overflows at the other time, it means that the red test lead is not connected to the grid, and other electrodes should be used to retest.
2. Detect the quality of IGBT
Set the pointer multimeter to the Rx10k block, connect the black test lead to the collector C of the IGBT, and the red test lead to the IGBT emitter E. At this time, the pointer of the multimeter is at the zero position. Touch the gate G and the collector C at the same time with your finger. At this time, the IGBT is triggered and turned on, and the pointer of the multimeter swings to the direction with the smaller resistance value, and can be fixed at a certain position. Then touch the gate G and the emitter E at the same time with your finger. At this time, the IGBT is blocked and the pointer of the multimeter returns to zero. If the measured situation is consistent with the above situation, it means that the tested IGBT is normal.
3. Check whether the IGBT contains a damping tube
To detect whether the IGBT contains a damping tube, the Rx1k block of the pointer multimeter can be used for detection, or the diode block of the digital multimeter can be used to measure the forward voltage drop of the PN junction for judgment. Use the two test pens of the pointer multimeter to measure the resistance of the G and E poles and the G and C poles of the IGBT in the forward and reverse directions. When the IGBT with the damping diode is normal, there is a forward resistance of about 4kΩ between the E and C poles), and the above measured values are all infinite. Finally, connect the red pen of the pointer multimeter to the C pole and the black pen to the E pole. If the measured value is about 3.5kΩ, the measured tube is an IGBT with a damping diode; if the measured value is about 50kΩ, then the measured IGBT Damping diode not included. For a digital multimeter, under normal circumstances, the forward voltage drop between the C and E poles of the IGBT is about 0.5V.
Any analog multimeter can be used to detect IGBTs. Note that when judging whether the IGBT is good or bad, the multimeter must be set to the Rx10k block. Because the internal battery voltage of the multimeter in the Rx1k block and below is too low, the IGBT cannot be turned on when the test is good or bad, so it is impossible to judge the quality of the IGBT.
Because this tube is relatively "squeamish", it is easily charged by the induction of external electromagnetic fields or static electricity, and a small amount of charge can form a relatively high voltage on the inter-electrode capacitor, which will damage the tube. Therefore, you should be extra careful when using a digital multimeter to detect IGBTs, and take corresponding anti-static induction measures. For example, before measuring, short-circuit the human body to the ground, and then touch the pins of the IGBT. It is best to connect a wire on the wrist to connect with the ground, so that the human body and the ground maintain an equipotentiality, and then touch the pins.
