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IGBT Modules definition

The IGBT module is the abbreviation of the Isolated Gate Bipolar Transistor. It is a new type of composite power electronic device that was born in the early 1980s and developed rapidly in the 1990s. The IGBT module is composed of a MOSFET field effect transistor and a BJT bipolar transistor. The input stage is a MOSFET and the output stage is a PNP high-power transistor. It combines the advantages of these two devices and has the advantages of a MOSFET device with high input impedance, fast response speed, good thermal stability and a simple drive circuit. , and has the advantages of low on-state voltage, high withstand voltage and large output current of bipolar devices. Its frequency characteristics are between MOS-FET and power transistors, and it can work normally in the frequency range of tens of kHz. In modern power electronics It has been increasingly widely used in technology and occupies a dominant position in high-frequency and medium-power applications. The turn-on and turn-off of the IGBT module is controlled by the gate voltage.

When a positive voltage is applied to the gate, a channel is formed in the MOSFET and provides base current for the PNP transistor, thereby turning on the IGBT module. At this time, the high-voltage IGBT module also has a low on-state voltage drop on the gate. When a negative voltage is applied, the channel in the MOSFET disappears, the base current of the PNP transistor is cut off, and the IGBT module is turned off. The IGBT module, like the MOSFET, is a voltage-controlled device. More than ten volts are applied between its gate and emitter. The DC voltage has only microampere leakage current and basically consumes no power, showing the advantage of large input impedance.

2. Replacement of IGBT module

Because the IGBT module works in a high-current and high-voltage state, has a high operating frequency, and generates a large amount of heat, its failure rate is high, and its price is high. Therefore, when replacing the IGBT module, the following principles should be followed: First, try to use Replacing the original model is not only conducive to fixed installation, but also relatively simple. Secondly, if there are no tubes of the same type, IGBT modules with similar parameters can be used to replace them. Generally, tubes with a larger rated current are used instead of tubes with a smaller rated current. Use high-voltage ones instead of low-voltage ones. If the parameters have been worn out, they can be replaced according to their rated power.

3. Storage of IGBT module

The temperature and humidity where semiconductor components are stored should be maintained at normal temperature and humidity, and should not deviate too much. Generally, normal temperature is 5 to 35 degrees Celsius, and normal humidity is 45% to 75%. In areas that are particularly dry in winter, humidification is required. The container for humidifying IGBT modules should be a non-static container and should be kept away from corrosive gases or places with a lot of dust. In places where the temperature changes drastically, there may be dew condensation on the surface of the IGBT module. Therefore, the IGBT module should be Place in a place where temperature changes are small.

4. Precautions for use

The gate of the IGBT module is electrically isolated from the emitter through an oxide film. Since this oxide film is very thin, the UGE voltage of the IGBT module is 20V. When a voltage exceeding the voltage is applied to the IGBT module, it will cause damage. Danger In addition, when the gate-emitter is open circuited, if a voltage is applied between the collector and the emitter, as the collector potential changes, leakage current flows through the collector, causing the gate potential to rise and the collector to Then there is current flowing through this time. If there is a high voltage between the collector and the emitter, it may cause the IGBT module to heat up or even be damaged. In applications, sometimes although it is ensured that the gate drive voltage does not exceed the maximum rated voltage of the gate, the gate The parasitic inductance of the electrode connection and the capacitive coupling between the gate and the collector will also produce an oscillation voltage that damages the oxide layer. For this reason, twisted pairs are usually used to transmit drive signals to reduce the parasitic inductance in the gate connection. A small resistor in series can also suppress the oscillation voltage. If the gate circuit is inappropriate or the gate circuit cannot work at all (the gate is in an open circuit state), if voltage is added to the main circuit, the IGBT module will be damaged. To prevent this type of If damage occurs, a resistor of about 10 kΩ should be connected between the gate and the emitter.

In addition, since the IGBT module has a MOS structure, you must be very careful about static electricity. Therefore, please pay attention to the following points:

(1) When using the module or holding the subassembly, do not touch the drive terminal part. When you must touch the module terminal, you must first discharge the static electricity on the human body or clothes before touching;

(2) When using conductive materials to connect the drive terminals of the IGBT module, please do not connect the module until the wiring is connected;

(3) Try to operate when the base plate is well grounded. For example, when welding, the soldering iron must be reliably grounded. When installing or replacing the IGBT module, great attention should be paid to the contact surface condition and tightening degree of the IGBT module and the heat sink. In order to reduce the contact thermal resistance , it is best to apply thermal conductive silicone grease between the radiator and the IGBT module. Generally, a cooling fan is installed at the bottom of the heat sink. When the cooling fan is damaged and the heat sink dissipates poorly, it will cause the IGBT module to heat up and malfunction. Therefore, the cooling fan should be inspected regularly. To check, there is usually a temperature sensor installed on the heat sink close to the IGBT module. When the temperature is too high, it will alarm or stop the IGBT module.

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