Teach you how to detect IGBT good or bad
The quality of the IGBT tube can be detected by the Rxlk block of the multimeter, or by using the “diode†block of the digital multimeter to measure the forward voltage drop of the PN junction. Before testing, short-circuit the three pins of the IGBT tube to avoid affecting the accuracy of the test; then use the two multimeters of the multimeter to measure the resistances of the G and e poles and the G and c poles. For normal IGBTs (normal The forward and backward resistances between the two poles of GE and Gc are infinite; the IGBTs with a damped diode are normal, and there are 4kΩ forward resistances between the eC poles). The measured values ​​are all infinite; finally, the red of the pointer multimeter is used. The pen is connected 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 tube with a damped diode. If the measured value is about 50kΩ, the measured IGBT tube does not contain a damper diode. For digital multimeters, the forward voltage drop across the eC pole of the IGBT tube is approximately 0.5V under normal conditions. The schematic diagram of the detection of the IGBT tube containing the damper diode is shown in the figure. The connection of the test leads is infinite, except for the connection shown in the figure. If the measured resistance between the three pins of the IGBT is very small, it indicates that the pipe has broken down. If the measured resistance between the three pins of the IGBT is infinite, it indicates that the pipe has been damaged by an open circuit. In practice, IGBTs are mostly damaged by breakdown. The judgement of the quality of the power module is mainly the judgment of the freewheeling diode in the power module. For the IGBT module, we also need to determine whether it can turn on and off under the trigger voltage. Inverter IGBT module detection: Put the digital multimeter to the diode test file and test the positive and negative diode characteristics between the IGBT modules c1 e1, c2 e2 and the gate G and e1, e2 to judge whether the IGBT module is in good condition. Take the six-phase module as an example. Remove the U-, V-, and W-phase conductors on the load side. Use the diode test file. Connect the red probe to P (collector c1). The black probes measure U, V, and W in turn. The multimeter displays the highest value. The test leads are reversed and black. The pens are connected to P, and the red pens measure U, V, W. The multimeter shows a value of about 400. Then the red table pen is connected to N (emitter e2), black table pen to measure U, V, W, multimeter display value is about 400; black table pen to P, red table pen to measure U, V, W, multimeter display value is the largest. The positive and negative characteristics between the phases should be the same. If there is a difference, it indicates that the performance of the IGBT module has deteriorated and should be replaced. When the IGBT module is damaged, only a short circuit occurs. The red and black markers respectively measure the forward and reverse characteristics between the gate G and the emitter E, and the values ​​measured twice by the multimeter are the maximum. At this time, it can be determined that the gate of the IGBT module is normal. If a value is displayed, the performance of the gate becomes poor and the module should be replaced. When the forward and reverse test results are zero, it indicates that the detected one-phase gate has been broken through. When the gate is damaged, the voltage regulator of the circuit board protection gate also breaks down and damages the variable frequency speed control system. After the induction motor is determined, the frequency converter should normally be selected according to the rated parameters of the asynchronous motor or the actual operating parameters of the motor. It has been found in practice that a high degree of attention should be given to the selection of the rated current of the frequency converter. If you select the inverter and only consider the capacity and do not consider the current, it is very easy to cause the inverter to burn. Therefore, there must be room for proper calculation of the inverter capacity. Usually require the rated current of the inverter: ≥ (1.05 ~ 1.1) IN (1) or I change ≥ (1.05 ~ 1.1) IMAX (2) I change----the rated current of the inverter IN---- Rated current of the motor IMAX----The maximum current in the actual operation of the motor When selected by capacity, the inverter capacity: P change ≥ 1.732 & TImes; KINUN10-3 (KVA) (3) In the formula IN----Motor rated current UN----Motor rated voltage K----safety factor, generally selected (1.05~1.1) For example, the selected motor has a rated voltage of UN=380V and a rated current of IN=7.2A. According to formula (1), the rated current of the inverter is selected: I becomes ≥1.1IN=1.1&TImes; 7.2=7.92(A) According to the formula (3) converter capacity selection: P variable ≥ 1.732 & TImes; 1.05 & TImes; 7.2 × 380 × 10-3 = 4.98 (KVA) Based on the above calculations, the inverter can select inverters with power ≥5KVA and rated current ≥8A. Judgment polarity Set the multimeter to R×1KΩ, when measuring with a multimeter, fix the black lead to one electrode, and the other (red lead) to the other two pins respectively. If the resistances are infinite, call Red. The test leads are fixed on this electrode (the pin that the original black lead was connected to), and the other leads (black lead) are connected to the other two pins respectively. If the resistances are infinite, the test lead is fixed. The connected pin is the gate. The other two poles are then measured with a multimeter. If the measured resistance is infinite, change the meter to measure the resistance. In the measurement of a small resistance value, it is determined that the red pen is connected to the drain (D); the black pen is connected to the source (S). Good or bad judgment Set the multimeter to R×10KΩ, connect the black lead to the drain (D) of the IGBT, and connect the red lead to the source (S) of the IGBT. At this time, the pointer of the multimeter is pointing at infinity. Touching the gate (G) and drain (D) at the same time with your finger, the IGBT is triggered to conduct. The pointer of the multimeter swings to a direction with a smaller resistance, and can stand in a certain position. Then touch the source (S) and the gate (G) at the same time with your fingers. At this time, the IGBT is blocked and the pointer of the multimeter returns to infinity. At this point, it can be judged that the IGBT is good. Note: If you enter the second measurement, short the source (S) and the gate (G). Any analog multimeter can be used to detect IGBTs. Note that when judging the IGBT is good or bad, be sure to set the multimeter to R×10KΩ, because the internal battery voltage of each multimeter of R×1K Ω is too low, the IGBT cannot be turned on when the test is good or bad, and the IGBT cannot be judged well. Bad. This method can also be used to detect the quality of power MOSFETs (P-MOSFETs).
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